1.  S., Lovato; G., Vaz; L., Toxopeus S; G., Keetels; J., Settels: Code Verification exercise for 2D Poiseuille flow with nonNewtonian fluid. 21th Numerical Towing Tank Symposium (NuTTS), Cortona, Italy, 2018. (Type: Conference  Links  BibTeX) @conference{2018NuTTSLovato, title = {Code Verification exercise for 2D Poiseuille flow with nonNewtonian fluid}, author = {Lovato S. and Vaz G. and Toxopeus S. L. and Keetels G. and Settels J.}, url = {http://www.refresco.org/download/codeverificationexercisefor2dpoiseuilleflowwithnonnewtonianfluid/}, year = {2018}, date = {20181001}, booktitle = {21th Numerical Towing Tank Symposium (NuTTS)}, address = {Cortona, Italy}, keywords = {}, pubstate = {published}, tppubtype = {conference} } 
2.  Eca, Luis; Klaij, Christiaan; Vaz, Guilherme; Hoekstra, Martin; Pereira, Filipe: On code verification of RANS solvers. In: Journal of Computational Physics, 310 , pp. 418439, 2016. (Type: Journal Article  Abstract  Links  BibTeX) @article{2016JCPEcaKlaijVazPereiraHoekstra, title = {On code verification of RANS solvers}, author = {Luis Eca and Christiaan Klaij and Guilherme Vaz and Martin Hoekstra and Filipe Pereira}, url = {http://www.refresco.org/download/2016jcpecaklaijvazpereirahoekstra_codeverification/}, year = {2016}, date = {20160113}, journal = {Journal of Computational Physics}, volume = {310}, pages = {418439}, abstract = {This article discusses Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddyviscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple onedimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for nonorthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article discusses Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddyviscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple onedimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for nonorthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities. 
3.  Eca, Luis; Vaz, Guilherme; Hoekstra, Martin: CODE VERIFICATION OF REFRESCO WITH A STATISTICALLY PERIODIC MANUFACTURED SOLUTION. OMAE2014 San Francisco, California, 2014. (Type: Conference  Abstract  Links  BibTeX) @conference{2014_OMAE23258_MMS+Unsteady_Eca_et_al, title = {CODE VERIFICATION OF REFRESCO WITH A STATISTICALLY PERIODIC MANUFACTURED SOLUTION}, author = {Luis Eca and Guilherme Vaz and Martin Hoekstra}, url = {http://www.refresco.org/download/2014_omae23258_mmsunsteady_eca_et_al/}, year = {2014}, date = {20140606}, address = {San Francisco, California}, organization = {OMAE2014}, abstract = {This paper presents a Code Verification study performed with the unsteady ensembleaveraged NavierStokes (URANS) solver ReFRESCO using the Method of Manufactured Solutions. The study uses a statistically periodic manufactured solution including the undamped eddyviscosity of the Spalart & Allmaras turbulence model. Three main aspects of the numerical calculations of unsteady flows are addressed in this study: iterative errors; discretization errors (space and time) and the determination of the observed order of (space and time) convergence. The availability of an exact solution allows the determination of the numerical error and so the effects of iterative and discretization errors can be addressed. The paper presents grid and time refinement studies with different (iterative) convergence criteria and demonstrates that grid and time resolution are strongly connected when attempts are made to minimize the numerical uncertainty in the calculation of unsteady flows. The paper also addresses error estimation based on power series expansions in the calculation of unsteady (space and time dependent) flows. Simultaneous grid and time refinement is compared to grid refinement with fixed time step and time refinement with fixed grid. The advantages and limitations of both options are discussed in the context of Code Verification (error evaluation) and Solution Verification (error estimation).}, keywords = {}, pubstate = {published}, tppubtype = {conference} } This paper presents a Code Verification study performed with the unsteady ensembleaveraged NavierStokes (URANS) solver ReFRESCO using the Method of Manufactured Solutions. The study uses a statistically periodic manufactured solution including the undamped eddyviscosity of the Spalart & Allmaras turbulence model. Three main aspects of the numerical calculations of unsteady flows are addressed in this study: iterative errors; discretization errors (space and time) and the determination of the observed order of (space and time) convergence. The availability of an exact solution allows the determination of the numerical error and so the effects of iterative and discretization errors can be addressed. The paper presents grid and time refinement studies with different (iterative) convergence criteria and demonstrates that grid and time resolution are strongly connected when attempts are made to minimize the numerical uncertainty in the calculation of unsteady flows. The paper also addresses error estimation based on power series expansions in the calculation of unsteady (space and time dependent) flows. Simultaneous grid and time refinement is compared to grid refinement with fixed time step and time refinement with fixed grid. The advantages and limitations of both options are discussed in the context of Code Verification (error evaluation) and Solution Verification (error estimation). 
4.  Pereira, Filipe: Verication of ReFRESCO with the Method of Manufactured Solutions. IST, Lisbon, Portugal, 2012. (Type: Masters Thesis  Abstract  Links  BibTeX) @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 = {}, 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. 
5.  Eca, Luis; Hoekstra, Martin; Vaz, Guilherme: On the use of Method of Manufactured Solutions for Code Verification of RANS solvers based on Eddyviscosity Models. 02.05.2012. (Type: Presentation  Abstract  Links  BibTeX) @misc{2012ASMEV&V6140_Eca, title = {On the use of Method of Manufactured Solutions for Code Verification of RANS solvers based on Eddyviscosity Models}, author = {Luis Eca and Martin Hoekstra and Guilherme Vaz}, url = {http://www.refresco.org/download/2012asmevv6140_ecahoekstravazmmsrans/}, year = {2012}, date = {20120502}, abstract = {This presentation discusses the use of Manufactured Solutions for Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers. In this exercise we will focus on timeaveraged (statistically steady), incompressible flows. Recently, we have developed several Manufactured Solutions (MS) that mimic a nearwall turbulent flow. The proposed analytical functions cover the mean flow quantities and the dependent variables of several eddyviscosity turbulence models. Namely, the undamped eddyviscosity of the Spalart & Allmaras and Menter oneequations models, k^(1/2) L from the one (SKL) and twoequation (KSKL) models proposed by Menter, the turbulence kinetic energy and the turbulence frequency included in twoequation kw models. The turbulence quantities are defined from “automatic wall functions” and so they are supposed to reproduce the expected behaviour of these variables. All flow fields satisfy mass conservation, i.e. mean velocity fields are divergence free. We address three types of exercises: 1. Calculation of the continuity and momentum equations with a manufactured eddyviscosity field. 2. Calculation of the turbulence quantities transport equations with the manufactured mean flow field. 3. Calculation of the complete system of equations. Two main topics are discussed: The effect of the turbulence model on the convergence properties of the RANS solver. The difficulties imposed to the Method of Manufactured Solutions by the fact that physically all turbulence quantities must remain positive.}, keywords = {}, pubstate = {published}, tppubtype = {presentation} } This presentation discusses the use of Manufactured Solutions for Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers. In this exercise we will focus on timeaveraged (statistically steady), incompressible flows. Recently, we have developed several Manufactured Solutions (MS) that mimic a nearwall turbulent flow. The proposed analytical functions cover the mean flow quantities and the dependent variables of several eddyviscosity turbulence models. Namely, the undamped eddyviscosity of the Spalart & Allmaras and Menter oneequations models, k^(1/2) L from the one (SKL) and twoequation (KSKL) models proposed by Menter, the turbulence kinetic energy and the turbulence frequency included in twoequation kw models. The turbulence quantities are defined from “automatic wall functions” and so they are supposed to reproduce the expected behaviour of these variables. All flow fields satisfy mass conservation, i.e. mean velocity fields are divergence free. We address three types of exercises: 1. Calculation of the continuity and momentum equations with a manufactured eddyviscosity field. 2. Calculation of the turbulence quantities transport equations with the manufactured mean flow field. 3. Calculation of the complete system of equations. Two main topics are discussed: The effect of the turbulence model on the convergence properties of the RANS solver. The difficulties imposed to the Method of Manufactured Solutions by the fact that physically all turbulence quantities must remain positive. 
6.  Abeil, Bastien: Validation of a RANS Code in the Handling of FreeSurface Flows. Chalmers University, Gothenburg, Sweden, 2007. (Type: Masters Thesis  Abstract  Links  BibTeX) @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 = {}, 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. 
2018 

S., Lovato; G., Vaz; L., Toxopeus S; G., Keetels; J., Settels Code Verification exercise for 2D Poiseuille flow with nonNewtonian fluid Conference 21th Numerical Towing Tank Symposium (NuTTS), Cortona, Italy, 2018. Links  BibTeX  Tags: Code Verification, nonnewtonian, ReFRESCO @conference{2018NuTTSLovato, title = {Code Verification exercise for 2D Poiseuille flow with nonNewtonian fluid}, author = {Lovato S. and Vaz G. and Toxopeus S. L. and Keetels G. and Settels J.}, url = {http://www.refresco.org/download/codeverificationexercisefor2dpoiseuilleflowwithnonnewtonianfluid/}, year = {2018}, date = {20181001}, booktitle = {21th Numerical Towing Tank Symposium (NuTTS)}, address = {Cortona, Italy}, keywords = {Code Verification, nonnewtonian, ReFRESCO}, pubstate = {published}, tppubtype = {conference} }  
2016 

Eca, Luis; Klaij, Christiaan; Vaz, Guilherme; Hoekstra, Martin; Pereira, Filipe On code verification of RANS solvers Journal Article Journal of Computational Physics, 310 , pp. 418439, 2016. Abstract  Links  BibTeX  Tags: Code Verification, Manufactured solutions, Numerical error, Order of grid convergence, RANS @article{2016JCPEcaKlaijVazPereiraHoekstra, title = {On code verification of RANS solvers}, author = {Luis Eca and Christiaan Klaij and Guilherme Vaz and Martin Hoekstra and Filipe Pereira}, url = {http://www.refresco.org/download/2016jcpecaklaijvazpereirahoekstra_codeverification/}, year = {2016}, date = {20160113}, journal = {Journal of Computational Physics}, volume = {310}, pages = {418439}, abstract = {This article discusses Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddyviscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple onedimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for nonorthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities.}, keywords = {Code Verification, Manufactured solutions, Numerical error, Order of grid convergence, RANS}, pubstate = {published}, tppubtype = {article} } This article discusses Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddyviscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple onedimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for nonorthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities.  
2014 

Eca, Luis; Vaz, Guilherme; Hoekstra, Martin CODE VERIFICATION OF REFRESCO WITH A STATISTICALLY PERIODIC MANUFACTURED SOLUTION Conference OMAE2014 San Francisco, California, 2014. Abstract  Links  BibTeX  Tags: Code Verification, Manufactured solutions, ReFRESCO @conference{2014_OMAE23258_MMS+Unsteady_Eca_et_al, title = {CODE VERIFICATION OF REFRESCO WITH A STATISTICALLY PERIODIC MANUFACTURED SOLUTION}, author = {Luis Eca and Guilherme Vaz and Martin Hoekstra}, url = {http://www.refresco.org/download/2014_omae23258_mmsunsteady_eca_et_al/}, year = {2014}, date = {20140606}, address = {San Francisco, California}, organization = {OMAE2014}, abstract = {This paper presents a Code Verification study performed with the unsteady ensembleaveraged NavierStokes (URANS) solver ReFRESCO using the Method of Manufactured Solutions. The study uses a statistically periodic manufactured solution including the undamped eddyviscosity of the Spalart & Allmaras turbulence model. Three main aspects of the numerical calculations of unsteady flows are addressed in this study: iterative errors; discretization errors (space and time) and the determination of the observed order of (space and time) convergence. The availability of an exact solution allows the determination of the numerical error and so the effects of iterative and discretization errors can be addressed. The paper presents grid and time refinement studies with different (iterative) convergence criteria and demonstrates that grid and time resolution are strongly connected when attempts are made to minimize the numerical uncertainty in the calculation of unsteady flows. The paper also addresses error estimation based on power series expansions in the calculation of unsteady (space and time dependent) flows. Simultaneous grid and time refinement is compared to grid refinement with fixed time step and time refinement with fixed grid. The advantages and limitations of both options are discussed in the context of Code Verification (error evaluation) and Solution Verification (error estimation).}, keywords = {Code Verification, Manufactured solutions, ReFRESCO}, pubstate = {published}, tppubtype = {conference} } This paper presents a Code Verification study performed with the unsteady ensembleaveraged NavierStokes (URANS) solver ReFRESCO using the Method of Manufactured Solutions. The study uses a statistically periodic manufactured solution including the undamped eddyviscosity of the Spalart & Allmaras turbulence model. Three main aspects of the numerical calculations of unsteady flows are addressed in this study: iterative errors; discretization errors (space and time) and the determination of the observed order of (space and time) convergence. The availability of an exact solution allows the determination of the numerical error and so the effects of iterative and discretization errors can be addressed. The paper presents grid and time refinement studies with different (iterative) convergence criteria and demonstrates that grid and time resolution are strongly connected when attempts are made to minimize the numerical uncertainty in the calculation of unsteady flows. The paper also addresses error estimation based on power series expansions in the calculation of unsteady (space and time dependent) flows. Simultaneous grid and time refinement is compared to grid refinement with fixed time step and time refinement with fixed grid. The advantages and limitations of both options are discussed in the context of Code Verification (error evaluation) and Solution Verification (error estimation).  
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.  
Eca, Luis; Hoekstra, Martin; Vaz, Guilherme On the use of Method of Manufactured Solutions for Code Verification of RANS solvers based on Eddyviscosity Models Presentation 02.05.2012. Abstract  Links  BibTeX  Tags: Code Verification, Eddyviscosity, Manufactured solutions, RANS solvers @misc{2012ASMEV&V6140_Eca, title = {On the use of Method of Manufactured Solutions for Code Verification of RANS solvers based on Eddyviscosity Models}, author = {Luis Eca and Martin Hoekstra and Guilherme Vaz}, url = {http://www.refresco.org/download/2012asmevv6140_ecahoekstravazmmsrans/}, year = {2012}, date = {20120502}, abstract = {This presentation discusses the use of Manufactured Solutions for Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers. In this exercise we will focus on timeaveraged (statistically steady), incompressible flows. Recently, we have developed several Manufactured Solutions (MS) that mimic a nearwall turbulent flow. The proposed analytical functions cover the mean flow quantities and the dependent variables of several eddyviscosity turbulence models. Namely, the undamped eddyviscosity of the Spalart & Allmaras and Menter oneequations models, k^(1/2) L from the one (SKL) and twoequation (KSKL) models proposed by Menter, the turbulence kinetic energy and the turbulence frequency included in twoequation kw models. The turbulence quantities are defined from “automatic wall functions” and so they are supposed to reproduce the expected behaviour of these variables. All flow fields satisfy mass conservation, i.e. mean velocity fields are divergence free. We address three types of exercises: 1. Calculation of the continuity and momentum equations with a manufactured eddyviscosity field. 2. Calculation of the turbulence quantities transport equations with the manufactured mean flow field. 3. Calculation of the complete system of equations. Two main topics are discussed: The effect of the turbulence model on the convergence properties of the RANS solver. The difficulties imposed to the Method of Manufactured Solutions by the fact that physically all turbulence quantities must remain positive.}, keywords = {Code Verification, Eddyviscosity, Manufactured solutions, RANS solvers}, pubstate = {published}, tppubtype = {presentation} } This presentation discusses the use of Manufactured Solutions for Code Verification of ReynoldsAveraged Navier Stokes (RANS) solvers. In this exercise we will focus on timeaveraged (statistically steady), incompressible flows. Recently, we have developed several Manufactured Solutions (MS) that mimic a nearwall turbulent flow. The proposed analytical functions cover the mean flow quantities and the dependent variables of several eddyviscosity turbulence models. Namely, the undamped eddyviscosity of the Spalart & Allmaras and Menter oneequations models, k^(1/2) L from the one (SKL) and twoequation (KSKL) models proposed by Menter, the turbulence kinetic energy and the turbulence frequency included in twoequation kw models. The turbulence quantities are defined from “automatic wall functions” and so they are supposed to reproduce the expected behaviour of these variables. All flow fields satisfy mass conservation, i.e. mean velocity fields are divergence free. We address three types of exercises: 1. Calculation of the continuity and momentum equations with a manufactured eddyviscosity field. 2. Calculation of the turbulence quantities transport equations with the manufactured mean flow field. 3. Calculation of the complete system of equations. Two main topics are discussed: The effect of the turbulence model on the convergence properties of the RANS solver. The difficulties imposed to the Method of Manufactured Solutions by the fact that physically all turbulence quantities must remain positive.  
2007 

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. 