2018 

F., Pereira Towards Predictive ScaleResolving Simulations of Turbulent External Flows PhD Thesis Instituto Superior Tecnico, 2018. Abstract  Links  BibTeX  Tags: Chow Wing, Circular cylinder, DDES, EARSM, PANS, SRS, Validation, Verification @phdthesis{2018PhD_FilipePereira, title = {Towards Predictive ScaleResolving Simulations of Turbulent External Flows}, author = {Pereira F.}, url = {http://www.refresco.org/download/2018phd_filipepereirapdf/}, year = {2018}, date = {20180302}, school = {Instituto Superior Tecnico}, abstract = {This work investigates the requisites and aptitude of SRS methods to achieve modelling accuracies that allow their use for predictive computations of turbulent external flows with practical interest. Selected models are therefore examined through verification and validation exercises using representative flows as validation space: a circular cylinder in crossflow at Reynolds numbers of Re = 3.9E3 and 1.40E5 (statistically unsteady problems); flow around the KVLCC2 tanker at model and fullscale, Re = 4.6E6 and 2.03E9; and flow past a wing at ten degrees of angle of attack and Re = 4.0E6 (statistically steady problems). The analysed models are the DDES, IDDES, XLES, DXLES, and PANS methods. Such exercises are intended to i) estimate the requisites to reduce numerical and input errors below the modelling error; ii) quantify the modelling error; and iii) physically interpret the results to ascertain their validity. Various RANS closures are also evaluated for comparison with the SRS methods. The results illustrate the advantages of SRS methods in the prediction of statistically unsteady flows. Yet, their correct application is rife with challenges: demanding numerical requisites; difficulties setting appropriate boundaryconditions and computational domain; dependence on commutation errors; and the complexity involved in the selection of the physical resolution and closure strategy. A set of guidelines and conditions are proposed to accurately simulate turbulent wake flows driven by coherent structures. The study also shows that EARSM (RANS) closures might be an efficient alternative for some of these flow problems. On the other hand, for statistically steady flows the results indicate that SRS methods are less advantageous. In these cases, advanced RANS closures seem more adequate for predicting meanflow quantities.}, keywords = {Chow Wing, Circular cylinder, DDES, EARSM, PANS, SRS, Validation, Verification}, pubstate = {published}, tppubtype = {phdthesis} } This work investigates the requisites and aptitude of SRS methods to achieve modelling accuracies that allow their use for predictive computations of turbulent external flows with practical interest. Selected models are therefore examined through verification and validation exercises using representative flows as validation space: a circular cylinder in crossflow at Reynolds numbers of Re = 3.9E3 and 1.40E5 (statistically unsteady problems); flow around the KVLCC2 tanker at model and fullscale, Re = 4.6E6 and 2.03E9; and flow past a wing at ten degrees of angle of attack and Re = 4.0E6 (statistically steady problems). The analysed models are the DDES, IDDES, XLES, DXLES, and PANS methods. Such exercises are intended to i) estimate the requisites to reduce numerical and input errors below the modelling error; ii) quantify the modelling error; and iii) physically interpret the results to ascertain their validity. Various RANS closures are also evaluated for comparison with the SRS methods. The results illustrate the advantages of SRS methods in the prediction of statistically unsteady flows. Yet, their correct application is rife with challenges: demanding numerical requisites; difficulties setting appropriate boundaryconditions and computational domain; dependence on commutation errors; and the complexity involved in the selection of the physical resolution and closure strategy. A set of guidelines and conditions are proposed to accurately simulate turbulent wake flows driven by coherent structures. The study also shows that EARSM (RANS) closures might be an efficient alternative for some of these flow problems. On the other hand, for statistically steady flows the results indicate that SRS methods are less advantageous. In these cases, advanced RANS closures seem more adequate for predicting meanflow quantities.  
2016 

Gharraee, Behrad Numerical Simulation of Cavitation on a Tidal Turbine using ReFRESCO Masters Thesis Chalmers University of Technology, 2016. Abstract  Links  BibTeX  Tags: Cavitation, Current Turbines, KSKL, RANS, SST, URANS, Verification @mastersthesis{2016Msc_Thesis_Gharraee, title = {Numerical Simulation of Cavitation on a Tidal Turbine using ReFRESCO}, author = {Behrad Gharraee}, url = { http://www.refresco.org/download/2016msc_thesis_gharraeepdf/}, year = {2016}, date = {20160104}, address = {Gothenburg}, school = {Chalmers University of Technology}, abstract = {As renewable energies continue to grow their share in the global energy landscape, marine resources present an inexhaustible potential to provide the ever increasing human settlements energy demands. Tidal energy conversion technologies enjoy the benefits of the accurately predictable and highly reliable resources, while promising great power to weight ratio due to the relatively small size of the equipment compared with offshore wind for instance. There are various prototypes being tested today and some proposals are employing floating structures as the platform for the energy converters, the design of which is driven by the higher kinetic energy content of the streams close to the water surface. Such concepts increase the turbines susceptibility to cavitation. There has been very little explicit research performed on the cavitation behavior of tidal turbines and this thesis attempts to establish one such study to enable and promote future investigations. The specialized hydrodynamic RANS solver ReFRESCO is used with the builtin Sauer cavitation model. Structured grids have been employed. The effectiveness of an eddyviscosity modification method known as the Reboud correction is also subject of investigation for improving dynamic behavior of cavities. Two different turbulence models used are kOmega SST (SST2003) and kskL. A threebladed model scale Horizontal Axis Tidal Turbine (HATT) is numerically simulated in openwater conditions in an attempt to reproduce previous EFD results from the University of Southampton, thus validating the numerical procedures in use. The simulations are performed through three stages where initially a steady solution is obtained, then the simulation becomes transient and finally the cavitation model is switched on. The results are validated against experiments via nondimensionalized parameters for thrust and torque, which prove satisfactory. General flow shows good agreement with experimental observations and the cavity formation appears to be accurate regarding both its position and blade coverage. Interestingly a cavity is observed near the leading edge on the pressure side. The simulations fail to resolve the details near the closure line of the sheet cavity which is attributed to inadequate meshing resolution. Very little dynamic behavior of the cavity structure is observed specifically where a "horseshoe" cavity structure had been detected during EFD, which will be subject to future work.}, keywords = {Cavitation, Current Turbines, KSKL, RANS, SST, URANS, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } As renewable energies continue to grow their share in the global energy landscape, marine resources present an inexhaustible potential to provide the ever increasing human settlements energy demands. Tidal energy conversion technologies enjoy the benefits of the accurately predictable and highly reliable resources, while promising great power to weight ratio due to the relatively small size of the equipment compared with offshore wind for instance. There are various prototypes being tested today and some proposals are employing floating structures as the platform for the energy converters, the design of which is driven by the higher kinetic energy content of the streams close to the water surface. Such concepts increase the turbines susceptibility to cavitation. There has been very little explicit research performed on the cavitation behavior of tidal turbines and this thesis attempts to establish one such study to enable and promote future investigations. The specialized hydrodynamic RANS solver ReFRESCO is used with the builtin Sauer cavitation model. Structured grids have been employed. The effectiveness of an eddyviscosity modification method known as the Reboud correction is also subject of investigation for improving dynamic behavior of cavities. Two different turbulence models used are kOmega SST (SST2003) and kskL. A threebladed model scale Horizontal Axis Tidal Turbine (HATT) is numerically simulated in openwater conditions in an attempt to reproduce previous EFD results from the University of Southampton, thus validating the numerical procedures in use. The simulations are performed through three stages where initially a steady solution is obtained, then the simulation becomes transient and finally the cavitation model is switched on. The results are validated against experiments via nondimensionalized parameters for thrust and torque, which prove satisfactory. General flow shows good agreement with experimental observations and the cavity formation appears to be accurate regarding both its position and blade coverage. Interestingly a cavity is observed near the leading edge on the pressure side. The simulations fail to resolve the details near the closure line of the sheet cavity which is attributed to inadequate meshing resolution. Very little dynamic behavior of the cavity structure is observed specifically where a "horseshoe" cavity structure had been detected during EFD, which will be subject to future work.  
2015 

Rosetti, Guilherme University of Sao Paulo, USP, Brasil, 2015. Abstract  Links  BibTeX  Tags: 3DoF, Cylinder, Free Motion, FSI, Imposed Motion, LCTM, SAS, SRS, SST, Transition, Turbulence Models, URANS, Validation, Verification, VIV @phdthesis{2015phdgfrosettipdf, title = {Improvements in the Numerical Modeling of Turbulence and FluidStructure Interaction for the VortexInduced Vibrations of a Rigid Cylinder}, author = {Guilherme Rosetti}, url = {http://www.refresco.org/download/2015phdgfrosettipdf/}, year = {2015}, date = {20150902}, school = {University of Sao Paulo, USP, Brasil}, abstract = {This thesis presents the development, implementation and application of turbulence and laminarturbulent transition models and fluidstructure capabilities to address the vortexshedding and vortexinduced vibrations of a rigid cylinder. These numerical developments have been carried out in the computational fluid dynamics (CFD) code ReFRESCO. In the current work, an investigation of the performance of the turbulence modeling with k! SST in a broad range of Reynolds numbers is carried out identifying its modeling deficiencies for this flow. The implementation and systematic application of the scale adaptive simulations (SAS) and the local correlation transition model (LCTM), both combined with the SST, have improved the agreement with experimental results for the cylinder flow, in a novel contribution of this work. The application of verication and validation technique has allowed the estimation of numerical errors and uncertainties for the different models. That is also identified as a contribution of this thesis. The combination of SST modeling with imposed motions is carried out as well as with the SAS and LCTM for moderate Reynolds numbers, different vibration frequencies and amplitudes, which is considered novel, as few publications address this issue in extent. Regarding the freemoving cylinder capabilities, the present work brings contributions with the application of SST and SASSST with freemoving cylinder for the study of VIV of two degreesoffreedom, low mass ratio and moderate Reynolds numbers, higher than commonly seen in the literature. Finally, the investigation of the relative importance of turbulence effects on the freemoving cylinder and the imposedmotions case, with respect to the fixed case is carried out. A natural conjecture that has been raised early on this work and proved correct is that, for engineering applications, the choice of turbulence modeling strategy is less decisive when the cylinder is moving with prescribed motion and even less stringent, for free motions as the body response filters most of the higher order turbulence effects. That is a relevant observation as it might allow modeling simplifications and the application of CFD tools to a range of engineering problems.}, keywords = {3DoF, Cylinder, Free Motion, FSI, Imposed Motion, LCTM, SAS, SRS, SST, Transition, Turbulence Models, URANS, Validation, Verification, VIV}, pubstate = {published}, tppubtype = {phdthesis} } This thesis presents the development, implementation and application of turbulence and laminarturbulent transition models and fluidstructure capabilities to address the vortexshedding and vortexinduced vibrations of a rigid cylinder. These numerical developments have been carried out in the computational fluid dynamics (CFD) code ReFRESCO. In the current work, an investigation of the performance of the turbulence modeling with k! SST in a broad range of Reynolds numbers is carried out identifying its modeling deficiencies for this flow. The implementation and systematic application of the scale adaptive simulations (SAS) and the local correlation transition model (LCTM), both combined with the SST, have improved the agreement with experimental results for the cylinder flow, in a novel contribution of this work. The application of verication and validation technique has allowed the estimation of numerical errors and uncertainties for the different models. That is also identified as a contribution of this thesis. The combination of SST modeling with imposed motions is carried out as well as with the SAS and LCTM for moderate Reynolds numbers, different vibration frequencies and amplitudes, which is considered novel, as few publications address this issue in extent. Regarding the freemoving cylinder capabilities, the present work brings contributions with the application of SST and SASSST with freemoving cylinder for the study of VIV of two degreesoffreedom, low mass ratio and moderate Reynolds numbers, higher than commonly seen in the literature. Finally, the investigation of the relative importance of turbulence effects on the freemoving cylinder and the imposedmotions case, with respect to the fixed case is carried out. A natural conjecture that has been raised early on this work and proved correct is that, for engineering applications, the choice of turbulence modeling strategy is less decisive when the cylinder is moving with prescribed motion and even less stringent, for free motions as the body response filters most of the higher order turbulence effects. That is a relevant observation as it might allow modeling simplifications and the application of CFD tools to a range of engineering problems.  
2014 

Saraiva, Goncalo Solution of Flows Around Airfoils Using RANS with WallFunctions Masters Thesis IST, Lisbon, Portugal, 2014. Abstract  Links  BibTeX  Tags: Eppler, Foils, NACA 0012, RANS, SST, Validation, Verification, Wallfunctions @mastersthesis{2014Msc_Thesis_GoncaloSaraiva, title = {Solution of Flows Around Airfoils Using RANS with WallFunctions}, author = {Goncalo Saraiva}, url = { http://www.refresco.org/?wpdmpro=2014msc_thesis_goncalosaraivapdf}, year = {2014}, date = {20141024}, school = {IST, Lisbon, Portugal}, abstract = {The calculation of the friction forces is essential in hydrodynamic and offshore applications. However, the high gradients that exist in nearwall regions require the use of one of the following approaches: grids that are very fine near the wall to calculate the wall shearstress directly from its definition; or wallfunctions (WF) to calculate indirectly the wall shearstress and provide boundary conditions for the variables of the turbulence models. The objective of this thesis is to assess the validity of WF boundary conditions for the calculation of friction and pressure coefficients, as well as aerodynamic forces coefficients of a conventional and a laminar airfoil. The ReFRESCO solver was used to solve the RANS equations with the SST version of the eddyviscosity turbulence model. The main conclusions obtained were: WF can yield acceptable results if the Reynolds number is high enough to promote transition near the leading edge; if the laminar part of the flow is significant, the results are not realistic because WF lead to a fully turbulent flow; the results for the pressure and lift coefficient are always better than for friction and drag coefficients due to the direct connection of the wall shearstress with the last two; last but not least, the results of the WF approach are strongly dependent on the location of the first interior grid node, even at high Reynolds number.}, keywords = {Eppler, Foils, NACA 0012, RANS, SST, Validation, Verification, Wallfunctions}, pubstate = {published}, tppubtype = {mastersthesis} } The calculation of the friction forces is essential in hydrodynamic and offshore applications. However, the high gradients that exist in nearwall regions require the use of one of the following approaches: grids that are very fine near the wall to calculate the wall shearstress directly from its definition; or wallfunctions (WF) to calculate indirectly the wall shearstress and provide boundary conditions for the variables of the turbulence models. The objective of this thesis is to assess the validity of WF boundary conditions for the calculation of friction and pressure coefficients, as well as aerodynamic forces coefficients of a conventional and a laminar airfoil. The ReFRESCO solver was used to solve the RANS equations with the SST version of the eddyviscosity turbulence model. The main conclusions obtained were: WF can yield acceptable results if the Reynolds number is high enough to promote transition near the leading edge; if the laminar part of the flow is significant, the results are not realistic because WF lead to a fully turbulent flow; the results for the pressure and lift coefficient are always better than for friction and drag coefficients due to the direct connection of the wall shearstress with the last two; last but not least, the results of the WF approach are strongly dependent on the location of the first interior grid node, even at high Reynolds number.  
Corbineau, Erwan Verification of REFRESCO for forced roll oscillations Masters Thesis ENSTA, Brest, Bretagne, France, 2014. Abstract  Links  BibTeX  Tags: Deforminggrids, FreeSurface, Rolldamping, SST, URANS, Validation, Verification @mastersthesis{2014Msc_Thesis_ErwanCorbineau, title = {Verification of REFRESCO for forced roll oscillations}, author = {Erwan Corbineau}, url = {http://www.refresco.org/download/2014msc_thesis_erwancorbineau}, year = {2014}, date = {20140821}, school = {ENSTA, Brest, Bretagne, France}, abstract = {The knowledge of the behavior of a ship in a given sea state is an essential part in ship design. To predict the flow around the hull of a boat, CFD (Computational Fluid Dynamics) is especially appreciated, because it is a good alternative to timeconsuming and expensive experimental studies. MARIN has been developing for the ten last years REFRESCO, which is an inhouse CFD code. It solves the multiphase unsteady incompressible RANS (Reynolds Averaged NavierStokes) equations, which are complemented with turbulence models and volumefraction transport equations for different phases. The objective of this Master’s Thesis is to verify REFRESCO for roll motion. A hull section with bilge keels is tested and a forced oscillating roll motion is imposed to the hull section. The roll damping caused by the bilge keels is a viscous effect, and involves turbulence. It is then necessary to see how accurate is REFRESCO, for a case implying solving nonlinear equations like roll motion. The Master’s Thesis is based on the estimation of numerical uncertainty. The best numerical settings for the study are investigated, and the accuracy of the calculated results is assessed. Extensive sensitivity studies have been performed, such as the effect of the scale, y+, the damping gain, grid and time step refinement, and iterative convergence. Sensitivity studies for different foll parameters are also performed, such as roll period and amplitude and the center of rotation.}, keywords = {Deforminggrids, FreeSurface, Rolldamping, SST, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The knowledge of the behavior of a ship in a given sea state is an essential part in ship design. To predict the flow around the hull of a boat, CFD (Computational Fluid Dynamics) is especially appreciated, because it is a good alternative to timeconsuming and expensive experimental studies. MARIN has been developing for the ten last years REFRESCO, which is an inhouse CFD code. It solves the multiphase unsteady incompressible RANS (Reynolds Averaged NavierStokes) equations, which are complemented with turbulence models and volumefraction transport equations for different phases. The objective of this Master’s Thesis is to verify REFRESCO for roll motion. A hull section with bilge keels is tested and a forced oscillating roll motion is imposed to the hull section. The roll damping caused by the bilge keels is a viscous effect, and involves turbulence. It is then necessary to see how accurate is REFRESCO, for a case implying solving nonlinear equations like roll motion. The Master’s Thesis is based on the estimation of numerical uncertainty. The best numerical settings for the study are investigated, and the accuracy of the calculated results is assessed. Extensive sensitivity studies have been performed, such as the effect of the scale, y+, the damping gain, grid and time step refinement, and iterative convergence. Sensitivity studies for different foll parameters are also performed, such as roll period and amplitude and the center of rotation.  
2013 

Aurelle, Julian Prediction of Wave Loading from Steep Waves on Fixed Offshore Wind Turbines Masters Thesis Ecole Centrale de Nantes, France, 2013. Links  BibTeX  Tags: impacts, Regular Waves, Turbines, Validation, Verification @mastersthesis{2013Stage_Julian_Aurelle, title = {Prediction of Wave Loading from Steep Waves on Fixed Offshore Wind Turbines}, author = {Julian Aurelle}, url = {http://www.refresco.org/?wpdmpro=2013stage_julian_aurellepdf}, year = {2013}, date = {20131231}, school = {Ecole Centrale de Nantes, France}, keywords = {impacts, Regular Waves, Turbines, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} }  
Kuin, Roderick HYDRODYNAMIC IMPROVEMENTS OF A GENERIC SUBMARINE USING VISCOUS FLOW CALCULATIONS Masters Thesis University of Twente, Enschede, the Netherlands, 2013. Abstract  Links  BibTeX  Tags: Design, Drift, Manoeuvring, RANS, Rotation, SST, Submarines, Validation, Verification @mastersthesis{2013Msc_Thesis_RoderickKuin, title = {HYDRODYNAMIC IMPROVEMENTS OF A GENERIC SUBMARINE USING VISCOUS FLOW CALCULATIONS}, author = {Roderick Kuin}, url = {http://www.refresco.org/?wpdmpro=2013msc_thesis_roderickkuinpdf}, year = {2013}, date = {20131231}, school = {University of Twente, Enschede, the Netherlands}, abstract = {Generally, underwater vehicles such as gliders or submarines have a hull or fuselage shape with low drag properties. However, additional appendages are generally required for control or storage of equipment. These appendages induce additional resistance and may be detrimental to the quality of the inflow to the aft control surfaces or propeller. This, in turn, can lead to loss of propulsion performance or increase of vibrations and radiated noise. The underlying hydrodynamic mechanism is the penetration by the appendage of the boundary layer developing on the hull, which causes the formation of a socalled horseshoe vortex in a region of separated flow near the stagnation area on the appendage. Computational Fluid Dynamics (CFD) has matured to a state that it can be applied successfully to investigate and optimise the flow around ships and offshore structures. In this research, CFD is used to study the flow around a typical wingbody junction in order to obtain insight in how to suppress the horseshoe vortex that is wrapped around the appendage. A generic submarine hull shape has been selected and the impact of a range of modifications of the sail (sometimes called fin or fairwater) on the resistance, propulsion, manoeuvring and wake field have been investigated. To quantify the nonuniformity of the wake field, a socalled Wake Object Function (WOF) is used. The WOF is defined such that decreasing its value reduces the chance of (erosive) cavitation and radiated noise. This research presents the results of the CFD computations for a number of sail variants and discusses the changes in the flow in detail. Design guidelines regarding the most promising modifications have been developed. It is shown that a thicker and a tapered sail have a significant negative influence on the main hydrodynamic characteristics, however, quite significant improvements of the resistance as well as the wake quality can be obtained by properly designing the junction between the sail and the hull.}, keywords = {Design, Drift, Manoeuvring, RANS, Rotation, SST, Submarines, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } Generally, underwater vehicles such as gliders or submarines have a hull or fuselage shape with low drag properties. However, additional appendages are generally required for control or storage of equipment. These appendages induce additional resistance and may be detrimental to the quality of the inflow to the aft control surfaces or propeller. This, in turn, can lead to loss of propulsion performance or increase of vibrations and radiated noise. The underlying hydrodynamic mechanism is the penetration by the appendage of the boundary layer developing on the hull, which causes the formation of a socalled horseshoe vortex in a region of separated flow near the stagnation area on the appendage. Computational Fluid Dynamics (CFD) has matured to a state that it can be applied successfully to investigate and optimise the flow around ships and offshore structures. In this research, CFD is used to study the flow around a typical wingbody junction in order to obtain insight in how to suppress the horseshoe vortex that is wrapped around the appendage. A generic submarine hull shape has been selected and the impact of a range of modifications of the sail (sometimes called fin or fairwater) on the resistance, propulsion, manoeuvring and wake field have been investigated. To quantify the nonuniformity of the wake field, a socalled Wake Object Function (WOF) is used. The WOF is defined such that decreasing its value reduces the chance of (erosive) cavitation and radiated noise. This research presents the results of the CFD computations for a number of sail variants and discusses the changes in the flow in detail. Design guidelines regarding the most promising modifications have been developed. It is shown that a thicker and a tapered sail have a significant negative influence on the main hydrodynamic characteristics, however, quite significant improvements of the resistance as well as the wake quality can be obtained by properly designing the junction between the sail and the hull.  
Willemsen, Christiaan Improving Potential Flow Predictions for Ducted Propellers Masters Thesis University of Twente, Enschede, the Netherlands, 2013. Abstract  Links  BibTeX  Tags: Ducts, Propeller, RANS, RANSBEM Coupling, SST, Validation, Verification @mastersthesis{2013Msc_Thesis_ChrisWillemsen, title = {Improving Potential Flow Predictions for Ducted Propellers}, author = {Christiaan Willemsen}, url = {http://www.refresco.org/?wpdmpro=2013msc_thesis_chriswillemsenpdf}, year = {2013}, date = {20131213}, school = {University of Twente, Enschede, the Netherlands}, abstract = {The advantages of propulsion systems using a thrust generating duct around a propeller are well known in naval architecture. A ducted propeller is often employed to increase the efficiency and thrust of a highly loaded propeller. The flow accelerating duct can contribute to 50 % of the propulsor total thrust at zero ship speed. There are not many fast and accurate hydrodynamic prediction methods for the design phase of ducted propellers. Model tests are expensive, while computations based on the Reynoldsaveraged NavierStokes (RANS) equations require long CPU times. Therefore these approaches are not yet routinely used in the design process of propulsors. Currently the design process is mostly based on the use of potential flow methods, like the MARIN Boundary Element Method (BEM) PROCAL. This method is efficient and is able to deliver accurate predictions of the forces acting on open propellers, but it is less accurate when viscous flow effects become important such as is the case for ducted propellers. The goal of the present research is to investigate the flow around a ducted propeller using the MARIN inhousedeveloped RANS method ReFRESCO, with particular emphasis on the in influence of the viscous flow effects such as boundary layers, tip vortices and flow separation on the outer surface of the duct. The results obtained with RANS are used to improve the prediction of PROCAL. Finally a coupling between PROCAL and ReFRESCO is accomplished to include the viscous flow effects in an efficient way. The viscous flow over the duct is annalyzed using ReFRESCO, in which the propeller action is represented by body forces added to the righthandside of the momentum equations. These body forces are obtained from a PROCAL computation for the ducted propeller in which the propeller is represented as a discrete number of blades. Results of this approach show a good agreement between experiments and the numerical simulations: the forces differ less than 1 % around the design point of the ducted propeller.}, keywords = {Ducts, Propeller, RANS, RANSBEM Coupling, SST, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The advantages of propulsion systems using a thrust generating duct around a propeller are well known in naval architecture. A ducted propeller is often employed to increase the efficiency and thrust of a highly loaded propeller. The flow accelerating duct can contribute to 50 % of the propulsor total thrust at zero ship speed. There are not many fast and accurate hydrodynamic prediction methods for the design phase of ducted propellers. Model tests are expensive, while computations based on the Reynoldsaveraged NavierStokes (RANS) equations require long CPU times. Therefore these approaches are not yet routinely used in the design process of propulsors. Currently the design process is mostly based on the use of potential flow methods, like the MARIN Boundary Element Method (BEM) PROCAL. This method is efficient and is able to deliver accurate predictions of the forces acting on open propellers, but it is less accurate when viscous flow effects become important such as is the case for ducted propellers. The goal of the present research is to investigate the flow around a ducted propeller using the MARIN inhousedeveloped RANS method ReFRESCO, with particular emphasis on the in influence of the viscous flow effects such as boundary layers, tip vortices and flow separation on the outer surface of the duct. The results obtained with RANS are used to improve the prediction of PROCAL. Finally a coupling between PROCAL and ReFRESCO is accomplished to include the viscous flow effects in an efficient way. The viscous flow over the duct is annalyzed using ReFRESCO, in which the propeller action is represented by body forces added to the righthandside of the momentum equations. These body forces are obtained from a PROCAL computation for the ducted propeller in which the propeller is represented as a discrete number of blades. Results of this approach show a good agreement between experiments and the numerical simulations: the forces differ less than 1 % around the design point of the ducted propeller.  
2012 

Pereira, Filipe Verication of ReFRESCO with the Method of Manufactured Solutions Masters Thesis IST, Lisbon, Portugal, 2012. Abstract  Links  BibTeX  Tags: Code Verification, Convection schemes, Excentricity, MMS, Nonorthogonality, RANS, SST, Validation, Verification @mastersthesis{2012Msc_Thesis_FilipePereira, title = {Verication of ReFRESCO with the Method of Manufactured Solutions}, author = {Filipe Pereira}, url = {http://www.refresco.org/?wpdmpro=2012msc_thesis_filipepereirapdf}, year = {2012}, date = {20121001}, school = {IST, Lisbon, Portugal}, abstract = {The purpose of this Thesis was to Verify the RANS solver ReFRESCO. This analysis was executed over three distinct parts of the code: convection schemes, nonorthogonality and excentricity correctors. Moreover, it was performed the implementation and evaluation of the numerical properties of two nonorthogonality and three excentricity new correction methods. In order to execute the Verification of ReFRESCO, grid refinement studies were performed to check if the numerical error tend to zero with the correct order of grid convergence (theoretical order). The calculation of the numerical error required the use of the Method of Manufactured Solutions to create exact solutions of the RANS equations. Thus, three manufactured solutions were used, each one resembling a different flow. The main conclusions of the present Thesis were: the convection schemes are correctly coded; the Hybrid scheme order of grid convergence did not vary linearly with the blending factor and it tended to a step function with the increase of the ow complexity; the tests performed over the nonorthogonality correctors showed that these methods maintained the secondorder of the code while discarding the correctors originated a constant numerical error in the solution; in grids where the excentricity factor was independent from grid renement, compared to the noncorrected case (constant numerical error), the excentricity correctors (correctly implemented) decreased significantly the magnitude of the numerical error. However, these correctors only guaranteed rstorder accuracy.}, keywords = {Code Verification, Convection schemes, Excentricity, MMS, Nonorthogonality, RANS, SST, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The purpose of this Thesis was to Verify the RANS solver ReFRESCO. This analysis was executed over three distinct parts of the code: convection schemes, nonorthogonality and excentricity correctors. Moreover, it was performed the implementation and evaluation of the numerical properties of two nonorthogonality and three excentricity new correction methods. In order to execute the Verification of ReFRESCO, grid refinement studies were performed to check if the numerical error tend to zero with the correct order of grid convergence (theoretical order). The calculation of the numerical error required the use of the Method of Manufactured Solutions to create exact solutions of the RANS equations. Thus, three manufactured solutions were used, each one resembling a different flow. The main conclusions of the present Thesis were: the convection schemes are correctly coded; the Hybrid scheme order of grid convergence did not vary linearly with the blending factor and it tended to a step function with the increase of the ow complexity; the tests performed over the nonorthogonality correctors showed that these methods maintained the secondorder of the code while discarding the correctors originated a constant numerical error in the solution; in grids where the excentricity factor was independent from grid renement, compared to the noncorrected case (constant numerical error), the excentricity correctors (correctly implemented) decreased significantly the magnitude of the numerical error. However, these correctors only guaranteed rstorder accuracy.  
2011 

Otto, William NUMERICAL SIMULATIONS OF FLOW OVER AN AXIAL MARINE CURRENT TURBINE Masters Thesis Technical University of Delft, the Netherlands, 2011. Abstract  Links  BibTeX  Tags: Current Turbines, RANS, SST, Turbines, URANS, Validation, Verification @mastersthesis{2011Msc_Thesis_WilliamOtto, title = {NUMERICAL SIMULATIONS OF FLOW OVER AN AXIAL MARINE CURRENT TURBINE}, author = {William Otto}, url = {http://www.refresco.org/?wpdmpro=2011msc_thesis_williamottopdf}, year = {2011}, date = {20111011}, school = {Technical University of Delft, the Netherlands}, abstract = {The main objective of this Msc. thesis is to obtain and analyze numerical simulations of singlephase flow over an axial marine current turbine. A wide range of operating conditions is simulated. Great attention is paid to verification, validation and uncertainty analysis. As benchmark, a reference turbine with experimental data is used which is found in literature (A.S. Bahaj and W.M.J. Batten, 2005 [17]). The simulations were performed at model scale and scale effects were studied by using the same geometry at full scale Reynolds numbers. This thesis is limited to single phase flows, what means that cavitation and free surface effects are deliberately excluded. Only a uniform inflow is modeled and interaction between the turbine and other objects as walls, floors, mounting rigs or other turbines are not taken into account (’open water condition’). Because these aspects can play a significant roll in practical applications, the numerical method is chosen such that they can be implemented in future work, once verified and validated simulations of noninteracting, singlephase flow have been obtained. Because its ability to include the aforementioned effects, as well its the ability to study scale effects, the MARIN inhouse RANS solver ReFRESCO is used for the simulations. A geometrical description of the reference turbine was received from the original authors. This geometry is modified in order to obtain feasible calculations. First, the trailing edge had to be thickened in order to avoid troubles in the grid generation. Second, a new connection has been constructed between the blades and the hub. The original connection causes an unsteady wake which elongates the calculation time to weeks. With a new constructed blade to hub connection, the flow is less complex, reducing the calculation time to a couple of days per condition. The modeling error caused by the thickened trailing edge is studied by using two dimensional RANS calculations over a radial section of the turbine (r=R = 0:7). It is estimated that the sectional lift is reduced by 3.78% due to the thickened trailing edge. Also an increase in drag is obtained, which is estimated as 6.35%. The turbine power and axial loading is corrected for this effect. The modified blade to hub connection is taken into account as an additional uncertainty in the solutions. A verification and validation procedure is performed to estimate the numerical and modeling uncertainties. The largest component of the numerical uncertainty is the discretization error. This error is hard to quantify due to: 1) the unstructured grid approach what makes it hard to produce a series of geometrical similar grids, 2) the small refinement range limited by the available memory resources. Therefore, a conservative estimation is made by using a safety factor. The numerical uncertainty is estimated as U = 3:6% for the power coefficient CP and U = 4:8% for the axial loading coefficient CT . A cylindrical computational domain is used to represent the open water condition. Initially, the domain size was 8 turbine diameter wide in radial direction. Later it proved that this domain was too small to fully represent an undisturbed flow without (numerical) blockage effects. By systematically increasing the domain size, it is estimated that the modeling error caused by the too small domain is Udomain = 0:5% for CP and Udomain = 2:6% for CT . The calculation results at model scale (Re = 1:4 105) show a very good similarity with the experimental results for the power production as well as the axial loading. Due to the scatter in the experiments, it is not possible to follow an official validation procedure. The flow analysis at model scale shows a large area of laminar flow separation at the suction side of the blades. It can be said that the blades are in stall for a large part. The turbulence intensity shows the boundary layer at the blade is in the transitional region. Roughly half of the chord length has a laminar boundary layer, the second half is turbulent. The stall can be caused by the laminar boundary layer, what makes it a scale effect. The flow analysis at full scale Reynolds numbers Re = 5 106 does not show the large separation areas. A fully turbulent boundary layer is obtained and the flow stays to a great extend attached to the blade. As a consequence, the obtained axial loading and power coefficient is more than 10% higher than at model scale. This is a significant scale effect where designers of marine current turbines should be aware of.}, keywords = {Current Turbines, RANS, SST, Turbines, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The main objective of this Msc. thesis is to obtain and analyze numerical simulations of singlephase flow over an axial marine current turbine. A wide range of operating conditions is simulated. Great attention is paid to verification, validation and uncertainty analysis. As benchmark, a reference turbine with experimental data is used which is found in literature (A.S. Bahaj and W.M.J. Batten, 2005 [17]). The simulations were performed at model scale and scale effects were studied by using the same geometry at full scale Reynolds numbers. This thesis is limited to single phase flows, what means that cavitation and free surface effects are deliberately excluded. Only a uniform inflow is modeled and interaction between the turbine and other objects as walls, floors, mounting rigs or other turbines are not taken into account (’open water condition’). Because these aspects can play a significant roll in practical applications, the numerical method is chosen such that they can be implemented in future work, once verified and validated simulations of noninteracting, singlephase flow have been obtained. Because its ability to include the aforementioned effects, as well its the ability to study scale effects, the MARIN inhouse RANS solver ReFRESCO is used for the simulations. A geometrical description of the reference turbine was received from the original authors. This geometry is modified in order to obtain feasible calculations. First, the trailing edge had to be thickened in order to avoid troubles in the grid generation. Second, a new connection has been constructed between the blades and the hub. The original connection causes an unsteady wake which elongates the calculation time to weeks. With a new constructed blade to hub connection, the flow is less complex, reducing the calculation time to a couple of days per condition. The modeling error caused by the thickened trailing edge is studied by using two dimensional RANS calculations over a radial section of the turbine (r=R = 0:7). It is estimated that the sectional lift is reduced by 3.78% due to the thickened trailing edge. Also an increase in drag is obtained, which is estimated as 6.35%. The turbine power and axial loading is corrected for this effect. The modified blade to hub connection is taken into account as an additional uncertainty in the solutions. A verification and validation procedure is performed to estimate the numerical and modeling uncertainties. The largest component of the numerical uncertainty is the discretization error. This error is hard to quantify due to: 1) the unstructured grid approach what makes it hard to produce a series of geometrical similar grids, 2) the small refinement range limited by the available memory resources. Therefore, a conservative estimation is made by using a safety factor. The numerical uncertainty is estimated as U = 3:6% for the power coefficient CP and U = 4:8% for the axial loading coefficient CT . A cylindrical computational domain is used to represent the open water condition. Initially, the domain size was 8 turbine diameter wide in radial direction. Later it proved that this domain was too small to fully represent an undisturbed flow without (numerical) blockage effects. By systematically increasing the domain size, it is estimated that the modeling error caused by the too small domain is Udomain = 0:5% for CP and Udomain = 2:6% for CT . The calculation results at model scale (Re = 1:4 105) show a very good similarity with the experimental results for the power production as well as the axial loading. Due to the scatter in the experiments, it is not possible to follow an official validation procedure. The flow analysis at model scale shows a large area of laminar flow separation at the suction side of the blades. It can be said that the blades are in stall for a large part. The turbulence intensity shows the boundary layer at the blade is in the transitional region. Roughly half of the chord length has a laminar boundary layer, the second half is turbulent. The stall can be caused by the laminar boundary layer, what makes it a scale effect. The flow analysis at full scale Reynolds numbers Re = 5 106 does not show the large separation areas. A fully turbulent boundary layer is obtained and the flow stays to a great extend attached to the blade. As a consequence, the obtained axial loading and power coefficient is more than 10% higher than at model scale. This is a significant scale effect where designers of marine current turbines should be aware of.  
Toxopeus, Serge Practical application of viscousflow calculations for the simulation of manoeuvring ships PhD Thesis Technical University of Delft, the Netherlands, 2011, ISBN: ISBN 9789075757057. Abstract  Links  BibTeX  Tags: DARPA Suboff, Drag, DTMB 5415M, Esso Osaka, HTC, KCS, KVLCC2, Lift, Manoeuvring, RANS, Rotation, Series60, Ships, SST, Submarines, Validation, Verification, Yaw @phdthesis{2011PhDToxopeus, title = {Practical application of viscousflow calculations for the simulation of manoeuvring ships}, author = {Serge Toxopeus}, url = {http://www.refresco.org/?wpdmpro=2011phdtoxopeuspdf}, isbn = {ISBN 9789075757057}, year = {2011}, date = {20110509}, school = {Technical University of Delft, the Netherlands}, abstract = {The present work was initiated in order to improve traditional manoeuvring simulations based on empirical equations to model the forces and moments on the ship. With the evolution of the capability of viscousflow solvers to predict forces and moments on ships, it was decided to develop a practical method to simulate the manoeuvrability of ships in which viscousflow solvers are utilised and to investigate whether this improves the accuracy of manoeuvring predictions. To achieve this goal, the virtual captive test approach is adopted, because of the efficient use of computational resources compared to other methods. This procedure mimics the approach for manoeuvring simulations in which experimental PMM is used to obtain the forces and moments on the ship. This study extends the work of other researchers by providing extensive verification and validation of the predicted forces and moments on the hull and a detailed study of the sensitivity of the manoeuvring characteristics of the ship to changes in the hydrodynamic coefficients in the simulation model. Changes in the flow solvers were required to be able to calculate the flow around ships in rotational motion. These changes are discussed as well as the acceleration techniques that were developed to reduce the effort spent on grid generation and during the computations. In this thesis, it is demonstrated that good predictions of the loads on the hull in manoeuvring motion can be obtained for a wide range of ship types. The trends in the forces and moments as a function of the drift angle or yaw rate are simulated well. The verification studies provide useful insight into the in influence of grid density on the predicted forces and moments. In several cases, validation of the calculations failed, indicating modelling errors in the numerical results. In these cases, it was generally seen that the magnitude of the transverse force was underpredicted, while the magnitude of the yaw moment was overpredicted. For manoeuvring studies in the early design, the comparison errors are within acceptable levels. However, improvements remain desired and may be obtained using finer grids, larger domain sizes, different grid topologies with refinement in the wake of the ship, other turbulence models or incorporating free surface deformation. The manoeuvring prediction program SurSim has been used to simulate the manoeuvrability of the HTC. A procedure is proposed to derive the hydrodynamic coefficients required to model the forces and moments on the bare hull. This procedure is chosen to enable accurate modelling of the linearised behaviour for coursekeeping as well as realistic modelling of the harbour manoeuvring characteristics, and to enable the modelling of nonlinear manoeuvres accurately. To generate validation data for the manoeuvring predictions presented in this thesis, free sailing manoeuvring tests for the HTC were performed. This test campaign resulted in a very valuable data set which can be used for public validation studies. Besides obtaining general characteristics of the manoeuvrability of a singlescrew container ship, unique information has been obtained on the drift angles and rates of turn combined with propeller and rudder forces. Furthermore, repeat tests have been conducted for selected manoeuvres. Based on these tests, the uncertainty in the characteristic manoeuvring properties has been estimated. By using hydrodynamic manoeuvring coefficients derived from the CFD calculations, it has been shown that it is possible to improve the prediction of ship manoeuvres compared to predictions using coefficients based on empirical equations. A considerable improvement in the turning circle predictions was obtained. The prediction of the yaw checking and course keeping and initial turning abilities based on zigzag simulations improved as well, but further improvements are required for more reliable assessment of the manoeuvring performance. The sensitivity of the manoeuvring predictions to changes in the hydrodynamic coefficients was studied. It was found that for accurate predictions of the manoeuvrability using coefficients derived from CFD calculations, accurate predictions of especially the yawing moment must be made.}, keywords = {DARPA Suboff, Drag, DTMB 5415M, Esso Osaka, HTC, KCS, KVLCC2, Lift, Manoeuvring, RANS, Rotation, Series60, Ships, SST, Submarines, Validation, Verification, Yaw}, pubstate = {published}, tppubtype = {phdthesis} } The present work was initiated in order to improve traditional manoeuvring simulations based on empirical equations to model the forces and moments on the ship. With the evolution of the capability of viscousflow solvers to predict forces and moments on ships, it was decided to develop a practical method to simulate the manoeuvrability of ships in which viscousflow solvers are utilised and to investigate whether this improves the accuracy of manoeuvring predictions. To achieve this goal, the virtual captive test approach is adopted, because of the efficient use of computational resources compared to other methods. This procedure mimics the approach for manoeuvring simulations in which experimental PMM is used to obtain the forces and moments on the ship. This study extends the work of other researchers by providing extensive verification and validation of the predicted forces and moments on the hull and a detailed study of the sensitivity of the manoeuvring characteristics of the ship to changes in the hydrodynamic coefficients in the simulation model. Changes in the flow solvers were required to be able to calculate the flow around ships in rotational motion. These changes are discussed as well as the acceleration techniques that were developed to reduce the effort spent on grid generation and during the computations. In this thesis, it is demonstrated that good predictions of the loads on the hull in manoeuvring motion can be obtained for a wide range of ship types. The trends in the forces and moments as a function of the drift angle or yaw rate are simulated well. The verification studies provide useful insight into the in influence of grid density on the predicted forces and moments. In several cases, validation of the calculations failed, indicating modelling errors in the numerical results. In these cases, it was generally seen that the magnitude of the transverse force was underpredicted, while the magnitude of the yaw moment was overpredicted. For manoeuvring studies in the early design, the comparison errors are within acceptable levels. However, improvements remain desired and may be obtained using finer grids, larger domain sizes, different grid topologies with refinement in the wake of the ship, other turbulence models or incorporating free surface deformation. The manoeuvring prediction program SurSim has been used to simulate the manoeuvrability of the HTC. A procedure is proposed to derive the hydrodynamic coefficients required to model the forces and moments on the bare hull. This procedure is chosen to enable accurate modelling of the linearised behaviour for coursekeeping as well as realistic modelling of the harbour manoeuvring characteristics, and to enable the modelling of nonlinear manoeuvres accurately. To generate validation data for the manoeuvring predictions presented in this thesis, free sailing manoeuvring tests for the HTC were performed. This test campaign resulted in a very valuable data set which can be used for public validation studies. Besides obtaining general characteristics of the manoeuvrability of a singlescrew container ship, unique information has been obtained on the drift angles and rates of turn combined with propeller and rudder forces. Furthermore, repeat tests have been conducted for selected manoeuvres. Based on these tests, the uncertainty in the characteristic manoeuvring properties has been estimated. By using hydrodynamic manoeuvring coefficients derived from the CFD calculations, it has been shown that it is possible to improve the prediction of ship manoeuvres compared to predictions using coefficients based on empirical equations. A considerable improvement in the turning circle predictions was obtained. The prediction of the yaw checking and course keeping and initial turning abilities based on zigzag simulations improved as well, but further improvements are required for more reliable assessment of the manoeuvring performance. The sensitivity of the manoeuvring predictions to changes in the hydrodynamic coefficients was studied. It was found that for accurate predictions of the manoeuvrability using coefficients derived from CFD calculations, accurate predictions of especially the yawing moment must be made.  
Crepier, Pierre Validation of URANS CFD Code ReFRESCO Roll Damping Simulations Masters Thesis ENSTA, Brest, Bretagne, France, 2011. Abstract  Links  BibTeX  Tags: Bilgekeels, Rolldamping, ScaleEffects, SpalartAllmaras, SST, URANS, Validation, Verification @mastersthesis{2011Msc_Thesis_PierreCrepier, title = {Validation of URANS CFD Code ReFRESCO Roll Damping Simulations}, author = {Pierre Crepier}, url = {http://www.refresco.org/?wpdmpro=2011msc_thesis_pierrecrepierpdf}, year = {2011}, date = {20110331}, school = {ENSTA, Brest, Bretagne, France}, abstract = {Unsteady calculations of the flow around rolling hull sections have been carried out. Two cases have been considered : a rectangular hull with sharp bilges and a rectangular hull fitted with triangularshaped bilge keels. The doublebody approach has been used for the computations. Sensitivity studies have been carried out on the grid refinement, the timestep size and the iterative convergence. It shows that the dependence on the grid is larger than on the timestep and the convergence threshold. Indeed, in order to have a grid converged, fine meshes have to be used. Results show that the viscous damping coefficient decreases when refining all the parameters. Results have been compared with existing data published by Ikeda and Yeung. Calculations for the case with sharp bilges appear to be in very good agreement with experimental results reported by Ikeda. They confirm the linear behavior of the damping coefficient with the amplitude. Regarding the case with bilge keels, results show a linear behavior of the damping coefficient with the frequency which is a behavior confirmed by Ikeda. For this case, a fairly good agreement is found for nondimensional frequencies lower than 0:7. For these values a deviation lower than 10% is obtained. However we observe larger deviations at high frequencies. Those deviations are believed to be due to freesurface effects and wave making. So, computations involving the free surface leading to a damping coefficient taking the wave damping into account have to be carried out. Preliminary studies on turbulence modeling and scale effects have also been done. Changing the turbulence model from SST to SpalartAllmaras leads to a damping higher by 4:5% explained by a higher pressure on the hull. Generated vortices are observed to be rounder and closer to each other than with SST. For the study on scale effects, a geometrical scale factor of 1=50 have been used and the viscosity have been tuned to reach the full scale conditions. The results obtained do not show large deviation with the modelscale computation. Indeed a damping higher by 1:5% is obtained due to a pressure slightly higher on the hull but the vorticity do not change much between the modelscale and the fullscale calculations}, keywords = {Bilgekeels, Rolldamping, ScaleEffects, SpalartAllmaras, SST, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } Unsteady calculations of the flow around rolling hull sections have been carried out. Two cases have been considered : a rectangular hull with sharp bilges and a rectangular hull fitted with triangularshaped bilge keels. The doublebody approach has been used for the computations. Sensitivity studies have been carried out on the grid refinement, the timestep size and the iterative convergence. It shows that the dependence on the grid is larger than on the timestep and the convergence threshold. Indeed, in order to have a grid converged, fine meshes have to be used. Results show that the viscous damping coefficient decreases when refining all the parameters. Results have been compared with existing data published by Ikeda and Yeung. Calculations for the case with sharp bilges appear to be in very good agreement with experimental results reported by Ikeda. They confirm the linear behavior of the damping coefficient with the amplitude. Regarding the case with bilge keels, results show a linear behavior of the damping coefficient with the frequency which is a behavior confirmed by Ikeda. For this case, a fairly good agreement is found for nondimensional frequencies lower than 0:7. For these values a deviation lower than 10% is obtained. However we observe larger deviations at high frequencies. Those deviations are believed to be due to freesurface effects and wave making. So, computations involving the free surface leading to a damping coefficient taking the wave damping into account have to be carried out. Preliminary studies on turbulence modeling and scale effects have also been done. Changing the turbulence model from SST to SpalartAllmaras leads to a damping higher by 4:5% explained by a higher pressure on the hull. Generated vortices are observed to be rounder and closer to each other than with SST. For the study on scale effects, a geometrical scale factor of 1=50 have been used and the viscosity have been tuned to reach the full scale conditions. The results obtained do not show large deviation with the modelscale computation. Indeed a damping higher by 1:5% is obtained due to a pressure slightly higher on the hull but the vorticity do not change much between the modelscale and the fullscale calculations  
Peyro, Guillaume Analysis of Flows on Stabilizer Fins using ReFRESCO: 2D,3D, Static and Dynamic Eects Masters Thesis ENSTA, Brest, Bretagne, France, 2011. Abstract  Links  BibTeX  Tags: Imposed Motion, NACA 0015, RANS, SST, Stabilizer fins, URANS, Validation, Verification @mastersthesis{2011Msc_Thesis_GuilaumePeyro, title = {Analysis of Flows on Stabilizer Fins using ReFRESCO: 2D,3D, Static and Dynamic Eects}, author = {Guillaume Peyro}, url = { http://www.refresco.org/?wpdmpro=2011msc_thesis_guilaumepeyropdf}, year = {2011}, date = {20110301}, school = {ENSTA, Brest, Bretagne, France}, abstract = {Nowadays, Computational Fluid Dynamic (CFD) is becoming more and more important in the maritime field to investigate complex hydrodynamic phenomena, especially when combined with model tests. Conscious about this, the Maritime Research Institute of Netherlands (MARIN) developed its own CFD code called ReFRESCO. The aim of this study is to use CFD to investigate the flow on a NACA 0015 hydrofoil which represents a stabilizer n, and to compare CFD results with model tests of this n. For this study, first, 2D static computations are done with ReFRESCO which allows us to know the effects of numerical parameters (boundary conditions, domain dimensions, domain shape...) on the results. Using these results, similar 3D computations are performed and compared to the results of the model tests. Finally, preliminary dynamic computations are done in order to test some tools simulating the oscillation of the foil.}, keywords = {Imposed Motion, NACA 0015, RANS, SST, Stabilizer fins, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } Nowadays, Computational Fluid Dynamic (CFD) is becoming more and more important in the maritime field to investigate complex hydrodynamic phenomena, especially when combined with model tests. Conscious about this, the Maritime Research Institute of Netherlands (MARIN) developed its own CFD code called ReFRESCO. The aim of this study is to use CFD to investigate the flow on a NACA 0015 hydrofoil which represents a stabilizer n, and to compare CFD results with model tests of this n. For this study, first, 2D static computations are done with ReFRESCO which allows us to know the effects of numerical parameters (boundary conditions, domain dimensions, domain shape...) on the results. Using these results, similar 3D computations are performed and compared to the results of the model tests. Finally, preliminary dynamic computations are done in order to test some tools simulating the oscillation of the foil.  
2010 

LeGarrec, Morgan Verification and Validation of Viscous FreeSurface Flows around Ships with ReFRESCO Masters Thesis Ecole Centrale de Nantes, France, 2010. Abstract  Links  BibTeX  Tags: Fixed WavySurface, FreeSurface, Resistance, Series60, Validation, Verification, WigleyHull @mastersthesis{2010Msc_Thesis_MorganLeGarrec, title = {Verification and Validation of Viscous FreeSurface Flows around Ships with ReFRESCO}, author = {Morgan LeGarrec }, url = {http://www.refresco.org/?wpdmpro=2010msc_morganlegarrecpdf}, year = {2010}, date = {20101001}, school = {Ecole Centrale de Nantes, France}, abstract = {Viscousflow RANS solvers usually called Computational Fluid Dynamics (CFD) tools are being widely used nowadays to compute the flow around ship hulls. They permit to capture both potential and viscous components of the flow, and even to model the freesurface formed by the ship displacement. Additionally, contrary to the modelbasin modelscale experiments, CFD tools permit to compute the flow around the model and the prototype, i.e. the modelscale and the fullscale real ship. ReFRESCO is an inhouse RANS MARIN tool under development. It is very versatile regarding the nature of the problem as well as the grids used for the computation. The following thesis aims to check the accuracy and to test general numerical aspects of ReFRESCO calculations for two wellknown ships test cases: WigleyHull and Series 60 hull. Verification procedures are used whenever possible in order to ensure that the numerical errors are under control, and to consequently permit correct validation exercises. A thorough bibliography research on available experimental and numerical data has been done for these two test cases and it is shown in tabular form in this thesis. Three approaches are considered for tackling the flow around these ships including freesurface: 1. a doublebody model where the freesurface modeling is neglected and a symmetry surface is considered instead; 2. a composite method where the freesurface is computed using a potentialflow solver, RAPID, and afterwards considered as a wavy boundary surface in the viscousflow computation; 3. a fully freesurface capturing RANS approach where the freesurface is solved using ReFRESCO by means of additional modeling equations. For this last method, the one to be used in the future, only a preliminary first attempt has been done. For the WigleyHull, HO grids targeted for the other MARIN RANS solver PARNASSOS are used. Calculations using these grids are usually difficult to converge by general codes. In this thesis we show that it is possible, being however the computational demands high. For this ship only a doublebody approach has been used and several numerical studies performed: computational domain size, grid layout, grid stretching, grid size, discretization schemes, influence of turbulence models, influence of turbulence model boundary conditions (with and without socalled wallfunctions). In general, the results show that the domain size has a large influence on the results, that wallfunctions should not be used, that fluxlimiters decreased the order of accuracy of the higherorder QUICK convection scheme. The comparison of the numerically verified results with the ITTC57 estimate showed a small underprediction of the friction resistance. The numerical tests also showed a large discrepancy on the forces when using k }, keywords = {Fixed WavySurface, FreeSurface, Resistance, Series60, Validation, Verification, WigleyHull}, pubstate = {published}, tppubtype = {mastersthesis} } Viscousflow RANS solvers usually called Computational Fluid Dynamics (CFD) tools are being widely used nowadays to compute the flow around ship hulls. They permit to capture both potential and viscous components of the flow, and even to model the freesurface formed by the ship displacement. Additionally, contrary to the modelbasin modelscale experiments, CFD tools permit to compute the flow around the model and the prototype, i.e. the modelscale and the fullscale real ship. ReFRESCO is an inhouse RANS MARIN tool under development. It is very versatile regarding the nature of the problem as well as the grids used for the computation. The following thesis aims to check the accuracy and to test general numerical aspects of ReFRESCO calculations for two wellknown ships test cases: WigleyHull and Series 60 hull. Verification procedures are used whenever possible in order to ensure that the numerical errors are under control, and to consequently permit correct validation exercises. A thorough bibliography research on available experimental and numerical data has been done for these two test cases and it is shown in tabular form in this thesis. Three approaches are considered for tackling the flow around these ships including freesurface: 1. a doublebody model where the freesurface modeling is neglected and a symmetry surface is considered instead; 2. a composite method where the freesurface is computed using a potentialflow solver, RAPID, and afterwards considered as a wavy boundary surface in the viscousflow computation; 3. a fully freesurface capturing RANS approach where the freesurface is solved using ReFRESCO by means of additional modeling equations. For this last method, the one to be used in the future, only a preliminary first attempt has been done. For the WigleyHull, HO grids targeted for the other MARIN RANS solver PARNASSOS are used. Calculations using these grids are usually difficult to converge by general codes. In this thesis we show that it is possible, being however the computational demands high. For this ship only a doublebody approach has been used and several numerical studies performed: computational domain size, grid layout, grid stretching, grid size, discretization schemes, influence of turbulence models, influence of turbulence model boundary conditions (with and without socalled wallfunctions). In general, the results show that the domain size has a large influence on the results, that wallfunctions should not be used, that fluxlimiters decreased the order of accuracy of the higherorder QUICK convection scheme. The comparison of the numerically verified results with the ITTC57 estimate showed a small underprediction of the friction resistance. The numerical tests also showed a large discrepancy on the forces when using k  
Pengam, Benjamin NUMERICAL ACCURACY IN RANS SIMULATIONS OF THE FLOW AROUND A CYLINDER Masters Thesis ENSTA, Brest, Bretagne, France, 2010. Links  BibTeX  Tags: Cylinder, Separation, Transition, URANS, Validation, Verification, Vortexshedding @mastersthesis{2010Msc_Thesis_BenjaminPengam, title = {NUMERICAL ACCURACY IN RANS SIMULATIONS OF THE FLOW AROUND A CYLINDER}, author = {Benjamin Pengam}, url = {http://www.refresco.org/?wpdmpro=2010msc_thesis_benjaminpengampdf}, year = {2010}, date = {20100806}, school = {ENSTA, Brest, Bretagne, France}, keywords = {Cylinder, Separation, Transition, URANS, Validation, Verification, Vortexshedding}, pubstate = {published}, tppubtype = {mastersthesis} }  
Gubler, Roman Numerical Simulation of the Flow Around a Ship Hull Including Interaction Effects between Hull and Propeller Masters Thesis Ecole Polytechnique Federale de Lausanne, Switzerland, 2010. Abstract  Links  BibTeX  Tags: HTC, RANSBEM Coupling, Ships, Validation, Verification, Wakefield @mastersthesis{2010MSc_Thesis_RomanGubler, title = {Numerical Simulation of the Flow Around a Ship Hull Including Interaction Effects between Hull and Propeller}, author = {Roman Gubler}, url = {http://www.refresco.org/?wpdmpro=2010msc_thesis_romangublerpdf}, year = {2010}, date = {20100301}, school = {Ecole Polytechnique Federale de Lausanne, Switzerland}, abstract = {Propeller effects are usually neglected in computations of the flow around ship hulls since the inclusion of the complex rotating propeller geometry in a numerical viscous flow simulation is very time consuming in terms of preprocessing and requires a lot of computational resources. Various methods have emerged to approach the highly complex problem of including propeller action in the description of the flow field to allow for a more accurate prediction of forces and moments acting on the ship hull. The present work describes the implementation of a body force approach to model effects of the propeller action on the viscous flow around a ship hull, that is, the forces exerted by the propeller are included in the body force terms in the Reynolds averaged NavierStokes equations incorporated in a viscous flow solver. The propeller forces are computed in a separate potential flow code. Nonlinear interaction effects between the flow around the ship hull and the propeller are taken into account by an iterative solution procedure between the two sequentially coupled flow solvers. The implementation is tested in an open water condition associated with a uniform inflow field to assess the reliability of the approach in terms of the velocity induction caused be the propeller. Application to a benchmark ship results in an expected alteration of the flow structure when the propeller effects are included. The subsequent comparison to experimental measurements reveals encouraging results in terms of global and local quantities.}, keywords = {HTC, RANSBEM Coupling, Ships, Validation, Verification, Wakefield}, pubstate = {published}, tppubtype = {mastersthesis} } Propeller effects are usually neglected in computations of the flow around ship hulls since the inclusion of the complex rotating propeller geometry in a numerical viscous flow simulation is very time consuming in terms of preprocessing and requires a lot of computational resources. Various methods have emerged to approach the highly complex problem of including propeller action in the description of the flow field to allow for a more accurate prediction of forces and moments acting on the ship hull. The present work describes the implementation of a body force approach to model effects of the propeller action on the viscous flow around a ship hull, that is, the forces exerted by the propeller are included in the body force terms in the Reynolds averaged NavierStokes equations incorporated in a viscous flow solver. The propeller forces are computed in a separate potential flow code. Nonlinear interaction effects between the flow around the ship hull and the propeller are taken into account by an iterative solution procedure between the two sequentially coupled flow solvers. The implementation is tested in an open water condition associated with a uniform inflow field to assess the reliability of the approach in terms of the velocity induction caused be the propeller. Application to a benchmark ship results in an expected alteration of the flow structure when the propeller effects are included. The subsequent comparison to experimental measurements reveals encouraging results in terms of global and local quantities.  
2009 

Glebart, Matthieu Validation and verification of FreSCo for loads on moving cylinders Masters Thesis ENSTA, Brest, Bretagne, France, 2009. Links  BibTeX  Tags: Cylinder, Imposed Motion, SST, Validation, Verification @mastersthesis{2009Stage_MatthieuGlebart, title = {Validation and verification of FreSCo for loads on moving cylinders}, author = {Matthieu Glebart}, url = {http://www.refresco.org/?wpdmpro=2009stage_matthieuglebartpdf }, year = {2009}, date = {20091103}, school = {ENSTA, Brest, Bretagne, France}, keywords = {Cylinder, Imposed Motion, SST, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} }  
Chanony, Francois Validation and verification of FreSCo for viscous flows around oscillating bodies. Roll motion Masters Thesis ENSTA, Brest, Bretagne, France, 2009. Links  BibTeX  Tags: Rolldamping, SST, URANS, Validation, Verification @mastersthesis{2009Stage_FrancoisChanony, title = {Validation and verification of FreSCo for viscous flows around oscillating bodies. Roll motion}, author = {Francois Chanony}, url = {http://www.refresco.org/?wpdmpro=2009stage_francoischanonypdf}, year = {2009}, date = {20090901}, school = {ENSTA, Brest, Bretagne, France}, keywords = {Rolldamping, SST, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} }  
Delvoye, Simon Simulation and analysis of the flow around an underwater exhaust with FreSCo Masters Thesis ISITV, Toulon, France, 2009. Links  BibTeX  Tags: Design, Multiphase, RANS, Scoops, SpalartAllmaras, SST, URANS, Verification @mastersthesis{2009Msc_Thesis_SimonDelvoye, title = {Simulation and analysis of the flow around an underwater exhaust with FreSCo}, author = {Delvoye, Simon}, url = {http://www.refresco.org/?wpdmpro=2009msc_thesis_simondelvoyepdf }, year = {2009}, date = {20090807}, school = {ISITV, Toulon, France}, keywords = {Design, Multiphase, RANS, Scoops, SpalartAllmaras, SST, URANS, Verification}, pubstate = {published}, tppubtype = {mastersthesis} }  
2008 

Rijpkema, Douwe Numerical Simulation of SinglePhase and MultiPhase Flow over a NACA 0015 Hydrofoil Masters Thesis Technical University of Delft, the Netherlands, 2008. Abstract  Links  BibTeX  Tags: Cavitation, Drag, Lift, NACA 0015, RANS, URANS, Validation, Verification @mastersthesis{2008Msc_Thesis_DouweRijpkema, title = {Numerical Simulation of SinglePhase and MultiPhase Flow over a NACA 0015 Hydrofoil}, author = {Douwe Rijpkema}, url = {http://www.refresco.org/?wpdmpro=2008msc_thesis_douwerijpkemapdf}, year = {2008}, date = {20081107}, school = {Technical University of Delft, the Netherlands}, abstract = {In the design of marine propellers, cavitation  the phenomenon of vapour formation due to a pressure reduction at constant temperature  is associated with negative effects on the performance and lifespan of the propeller. Additionally cavitation can be a source of inboard and underwater noise. Therefore insight in the occurence of cavitation and the development of the cavity on a propeller is essential. The numerical simulation of this phenomenon with computational fluid dynamics (CFD) tools may play an important role in this analysis. In this study a numerical simulation of both wetted and cavitating flow over a NACA 0015 hydrofoil is performed. The foil is placed at an angle of attack of 6 degrees for a Reynolds number of 1.5E6. The CFD code FreSCo is used for the numerical simulations. FreSCo is an unsteady RANS solver actively being developed by a cooperation of Maritime Research Institute Netherlands (MARIN), Hamburgische SchiffbauVersuchsanstalt (HSVA) and Technische Universitaet HamburgHarburg (TUHH). In the computations, a MenterSST turbulence model is applied and a volume of fluid approach is used for the modelling of multiple phases. The influence of various numerical parameters on the hydrodynamic forces and cavitation behaviour is investigated. For wetted flow a variation in grid topology showed a significant influence on the lift. Computations with the Otype grid resulted in an increase in lift in comparison to the Ctype grid results. The Otype grid showed a better agreement with the pressure distributions obtained by other numerical methods. A refinement of the grid produced less variation in results for the QUICK scheme compared to the blending scheme for the convective flux term in the momentum equations. Therefore an Otype grid combined with a QUICK convection scheme is preferred for this type of flow. The comparison of the pressure distributions between FreSCo and two different boundary element methods showed a good agreement in results. In the case of cavitating flow, the cavitation model accounts for the creation and destruction of the vapour in the liquid. It gives an expression for the source term in the transport equation of the vapour volume fraction. A comparison was made between the Sauer, Zwart and Kunz cavitation models. The different formulations for the source term of the three models, led to large deviations in results and affected the numerical stability. It was observed that for the same cavitation model a reduction in tuning coefficient resulted in a smaller cavity and more numerically stable behaviour. For the high cavitation numbers ( = 1.75, = 1.5 and = 1.25) a steady attached cavity was found on the foil for all cavitation models. The different formulation of the various cavitation models resulted in a difference in hydrodynamic forces and cavity characteristics, becoming more pronounced with decreasing cavitation number. Due to the large source terms of the cavitation models, large pressure oscillations and consequently large lift and drag peaks were observed at low cavitation numbers ( = 1.0). A reduction of the timestep or of the condensation tuning coefficient resulted in a more stable computation. For = 1.0 shedding of the cavity was observed in the initial phase of the computation, eventually leading to an attached cavity on the foil that periodically varied in size}, keywords = {Cavitation, Drag, Lift, NACA 0015, RANS, URANS, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } In the design of marine propellers, cavitation  the phenomenon of vapour formation due to a pressure reduction at constant temperature  is associated with negative effects on the performance and lifespan of the propeller. Additionally cavitation can be a source of inboard and underwater noise. Therefore insight in the occurence of cavitation and the development of the cavity on a propeller is essential. The numerical simulation of this phenomenon with computational fluid dynamics (CFD) tools may play an important role in this analysis. In this study a numerical simulation of both wetted and cavitating flow over a NACA 0015 hydrofoil is performed. The foil is placed at an angle of attack of 6 degrees for a Reynolds number of 1.5E6. The CFD code FreSCo is used for the numerical simulations. FreSCo is an unsteady RANS solver actively being developed by a cooperation of Maritime Research Institute Netherlands (MARIN), Hamburgische SchiffbauVersuchsanstalt (HSVA) and Technische Universitaet HamburgHarburg (TUHH). In the computations, a MenterSST turbulence model is applied and a volume of fluid approach is used for the modelling of multiple phases. The influence of various numerical parameters on the hydrodynamic forces and cavitation behaviour is investigated. For wetted flow a variation in grid topology showed a significant influence on the lift. Computations with the Otype grid resulted in an increase in lift in comparison to the Ctype grid results. The Otype grid showed a better agreement with the pressure distributions obtained by other numerical methods. A refinement of the grid produced less variation in results for the QUICK scheme compared to the blending scheme for the convective flux term in the momentum equations. Therefore an Otype grid combined with a QUICK convection scheme is preferred for this type of flow. The comparison of the pressure distributions between FreSCo and two different boundary element methods showed a good agreement in results. In the case of cavitating flow, the cavitation model accounts for the creation and destruction of the vapour in the liquid. It gives an expression for the source term in the transport equation of the vapour volume fraction. A comparison was made between the Sauer, Zwart and Kunz cavitation models. The different formulations for the source term of the three models, led to large deviations in results and affected the numerical stability. It was observed that for the same cavitation model a reduction in tuning coefficient resulted in a smaller cavity and more numerically stable behaviour. For the high cavitation numbers ( = 1.75, = 1.5 and = 1.25) a steady attached cavity was found on the foil for all cavitation models. The different formulation of the various cavitation models resulted in a difference in hydrodynamic forces and cavity characteristics, becoming more pronounced with decreasing cavitation number. Due to the large source terms of the cavitation models, large pressure oscillations and consequently large lift and drag peaks were observed at low cavitation numbers ( = 1.0). A reduction of the timestep or of the condensation tuning coefficient resulted in a more stable computation. For = 1.0 shedding of the cavity was observed in the initial phase of the computation, eventually leading to an attached cavity on the foil that periodically varied in size  
Jaouen, Frederick The Validation of the FreeSurface Modelling of FRESCO Masters Thesis ENSTA, Brest, Bretagne, France, 2008. Abstract  Links  BibTeX  Tags: Duncan Foil, FreeSurface, Regular Waves, TransomStern Flows, Validation, Verification @mastersthesis{2008Msc_Thesis_FrederickJaouen, title = {The Validation of the FreeSurface Modelling of FRESCO}, author = {Frederick Jaouen}, url = {http://www.refresco.org/?wpdmpro=2008msc_thesis_frederickjaouenpdf}, year = {2008}, date = {20080801}, school = {ENSTA, Brest, Bretagne, France}, abstract = {The CFD code FRESCO – FREe Surface COde – is the result from a cooperation between HSVA (Hamburgische Schiffbau Versuch Anstalt), TUHH (Technische Universit¨at HamburgHarburg) and MARIN (MAritime Research Institute of the Netherlands). This code, whose mathematical formulation is based on the RANS equations (Reynolds Averaged NavierStokes), focuses on the resolution of multiphase flows, ie. free surface flows, cavitating flows, multispecies flows. In order to identify the modelling errors and reduce the iteration and discretization errors, any CFD code has to be validated. The purpose of this master’s thesis is the validation of the freesurface modelling of FRESCO, especially regarding wave generation and propagation. The study of the numerical dissipation and dispersion of Airy and Stokes waves is carried out. Finally, the Duncan experiments and Transom Stern flows are used for the validation. Basically the numerical results show good agreements with analytical solutions or experimental tests and conclusions are so quite optimistic. However, some specific boundary conditions seem to be required for wave problems and a more consistent way of discretizing the hydrostatic law at the interface has to be implemented.}, keywords = {Duncan Foil, FreeSurface, Regular Waves, TransomStern Flows, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The CFD code FRESCO – FREe Surface COde – is the result from a cooperation between HSVA (Hamburgische Schiffbau Versuch Anstalt), TUHH (Technische Universit¨at HamburgHarburg) and MARIN (MAritime Research Institute of the Netherlands). This code, whose mathematical formulation is based on the RANS equations (Reynolds Averaged NavierStokes), focuses on the resolution of multiphase flows, ie. free surface flows, cavitating flows, multispecies flows. In order to identify the modelling errors and reduce the iteration and discretization errors, any CFD code has to be validated. The purpose of this master’s thesis is the validation of the freesurface modelling of FRESCO, especially regarding wave generation and propagation. The study of the numerical dissipation and dispersion of Airy and Stokes waves is carried out. Finally, the Duncan experiments and Transom Stern flows are used for the validation. Basically the numerical results show good agreements with analytical solutions or experimental tests and conclusions are so quite optimistic. However, some specific boundary conditions seem to be required for wave problems and a more consistent way of discretizing the hydrostatic law at the interface has to be implemented.  
2007 

Monroy, Charles A RANSE BASED STUDY OF THE FLOW BEHIND A CYLINDER. A FIRST STEP TOWARDS RISER FLOW Masters Thesis Ecole Centrale de Nantes, France, 2007. Abstract  Links  BibTeX  Tags: Cylinder, SST, URANS, Validation, Verification, Vortexshedding @mastersthesis{2007Msc_Thesis_CharlesMonroy, title = {A RANSE BASED STUDY OF THE FLOW BEHIND A CYLINDER. A FIRST STEP TOWARDS RISER FLOW}, author = {Charles Monroy}, url = {http://www.refresco.org/?wpdmpro=2007msc_thesis_charlesmonroypdf }, year = {2007}, date = {20070927}, school = {Ecole Centrale de Nantes, France}, abstract = {The objective of this thesis is to validate the RANS solver FreSCo, developed by MARIN, in the case of the flow around a fixed smooth circular cylinder. Despite the simple geometry of the problem, the computation of the flow around a cylinder is perhaps one of the most challenging problems of fluid dynamics. It is also of prime interest for offshore applications, especially for riser flows. The study focuses on 2D computations and deals with the different types of flows for several Reynolds numbers. The main features of the flow, such as velocity, pressure distribution on the cylinder and vorticity, are presented. The results are compared with experimental data and other computational results from different sources. The study shows that FreSCo provides excellent results for the steady laminar flow (up to Re ∼ 47), and satisfying ones for the unsteady laminar flow (from Re ∼ 47 to Re ∼ 1000). For turbulent flows, although there are significant differences with the experiment, FreSCo results are comparable with the performances of other CFD codes}, keywords = {Cylinder, SST, URANS, Validation, Verification, Vortexshedding}, pubstate = {published}, tppubtype = {mastersthesis} } The objective of this thesis is to validate the RANS solver FreSCo, developed by MARIN, in the case of the flow around a fixed smooth circular cylinder. Despite the simple geometry of the problem, the computation of the flow around a cylinder is perhaps one of the most challenging problems of fluid dynamics. It is also of prime interest for offshore applications, especially for riser flows. The study focuses on 2D computations and deals with the different types of flows for several Reynolds numbers. The main features of the flow, such as velocity, pressure distribution on the cylinder and vorticity, are presented. The results are compared with experimental data and other computational results from different sources. The study shows that FreSCo provides excellent results for the steady laminar flow (up to Re ∼ 47), and satisfying ones for the unsteady laminar flow (from Re ∼ 47 to Re ∼ 1000). For turbulent flows, although there are significant differences with the experiment, FreSCo results are comparable with the performances of other CFD codes  
Manzke, Manuel Using FreSCo for the Determination of Frictional Forces Masters Thesis TUHH, Hamburg, Germany, 2007. Links  BibTeX  Tags: 1eq Menter, Drag, Flatplate, kepsilon, komega, SpalartAllmaras, SST, Turbulence Models, Validation, Verification, Wallfunctions @mastersthesis{2007Stage_ManuelManzke, title = {Using FreSCo for the Determination of Frictional Forces}, author = {Manuel Manzke}, url = {http://www.refresco.org/?wpdmpro=2007stage_manuelmanzkepdf}, year = {2007}, date = {20070504}, school = {TUHH, Hamburg, Germany}, keywords = {1eq Menter, Drag, Flatplate, kepsilon, komega, SpalartAllmaras, SST, Turbulence Models, Validation, Verification, Wallfunctions}, pubstate = {published}, tppubtype = {mastersthesis} }  
Abeil, Bastien Validation of a RANS Code in the Handling of FreeSurface Flows Masters Thesis Chalmers University, Gothenburg, Sweden, 2007. Abstract  Links  BibTeX  Tags: 2D dambreak, 3D dambreak, CICSAM, Code Verification, Convection schemes, FreeSurface, Validation, Verification @mastersthesis{2007Msc_Thesis_BastienAbeil, title = {Validation of a RANS Code in the Handling of FreeSurface Flows}, author = {Bastien Abeil}, url = {http://www.refresco.org/?wpdmpro=2007msc_thesis_bastienabeilpdf}, year = {2007}, date = {20070305}, school = {Chalmers University, Gothenburg, Sweden}, abstract = {The ever increasing demand for performances of CFD codes in terms of free surface flows has yielded developers of new RANS code FRESCO to focus on the possible ways to retain interfaces between two fluids as accurate as possible. To that extent, a fairly complete study of the existing discretization schemes designed to handle free surface flows has led to dress up a list of the most relevant ones in a view of numerical implementation within the code. The emphasis will then be put on the performances of the CICSAM scheme (developed by O. Ubbink). A wide range of computations carried out with this scheme on several test cases will lead to a conclusion regarding his performance. Finally, two different dambreak test cases will be performed, and the results from FRESCO will be compared with the ones obtained by a commercial code currently used (COMFLOW) and also with experimental data.}, keywords = {2D dambreak, 3D dambreak, CICSAM, Code Verification, Convection schemes, FreeSurface, Validation, Verification}, pubstate = {published}, tppubtype = {mastersthesis} } The ever increasing demand for performances of CFD codes in terms of free surface flows has yielded developers of new RANS code FRESCO to focus on the possible ways to retain interfaces between two fluids as accurate as possible. To that extent, a fairly complete study of the existing discretization schemes designed to handle free surface flows has led to dress up a list of the most relevant ones in a view of numerical implementation within the code. The emphasis will then be put on the performances of the CICSAM scheme (developed by O. Ubbink). A wide range of computations carried out with this scheme on several test cases will lead to a conclusion regarding his performance. Finally, two different dambreak test cases will be performed, and the results from FRESCO will be compared with the ones obtained by a commercial code currently used (COMFLOW) and also with experimental data. 
ReFRESCO related MSc and Phd ThesesGuilherme Vaz20190619T14:01:23+01:00
Cavitation Chow Wing Convection schemes Current Turbines Cylinder Drag FreeSurface Imposed Motion KSKL Lift Manoeuvring NACA 0015 Propeller RANS ReFRESCO Regular Waves Rolldamping Rotation ScaleEffects SpalartAllmaras SRS SST Transition Turbines Turbulence Models URANS Validation Verification Vortexshedding Wallfunctions