# OpenFOAM vs ANSYS Fluent (Solution and Schemes)

 Register Blogs Members List Search Today's Posts Mark Forums Read January 21, 2021, 08:27 OpenFOAM vs ANSYS Fluent (Solution and Schemes) #1 Member   Anonymous. Join Date: Sep 2020 Posts: 35 Rep Power: 5 Hi all, I am trying to replicate the simulation from ANSYS fluent to OpenFOAM but I could not find some settings or do not know how to set them in OF.(This is my way of learning, feel free to drop comment for a better way). The following are the areas I am looking at fvSolution and fvScheme in the OF settings. Currently there are 4 segments of input parameters I divided them into and each contains question as shown below: 1) The fvSolution algorithm used was PISO Fluent settings: Skewness Correction 1 Neighbor Correction 1 OF settings: PIMPLE { nNonOrthogonalCorrectors 1 nCorrectors 1 nOuterCorrectors 1 } Questions: When the simulation is running in fluent, there is an additional option of setting max iteration per timestep, does this iteration refer to total no. of PISO loop per timestep or the control of other loops? 2) fvSchemes grad and div settings fluent settings: gradient, leastsquareCellBased Pressure, Second Order upwind Momentum, Second Order upwind TKE, Second Order upwind TDR, Second Order upwind Energy, Second Order upwind Transient Formulation, First Order implicit OF settings: ddtSchemes { default Euler; } gradSchemes { default none; grad(U) leastSquares; grad(T) leastSquares; grad(k) leastSquares; grad(epsilon) leastSquares; grad(R) leastSquares; } divSchemes { default none; div(phi,U) Gauss linearUpwind grad(U); div(phi,T) Gauss linearUpwind grad(T); div(phi,k) Gauss linearUpwind grad(k); div(phi,epsilon) Gauss linearUpwind grad(epsilon); div(phi,R) Gauss linearUpwind grad(R); div(R) Gauss linearUpwind grad(R); div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear uncorrected; } interpolationSchemes { default linear; } snGradSchemes { default uncorrected; } Questions: Are the laplacianSchemes/interpolationschemes in fluent follow the individual schemes that are present? i.e. momentum follows all second order upwind for div, laplacian and interpolation schemes. Why can't set linearUpwind for div((nuEff*dev2(T(grad(U))))) under divSchemes? 3) fvSolution Residuals All settings are the same except for continuity and pressure. Does anyone know where to set the Pressure residuals in fluent? Does anyone know where to set the continuity Residuals in OF? 4) fvSolution Under-Relaxation Factors Fluent settings: Pressure 0.3 Density 1 Body Forces 1 Momentum 0.7 TKE 0.8 TDR 0.8 Turbulent Viscosity 1 Energy 1 OF settings: Momentum 0.7 TKE 0.8 TDR 0.8 Question: How do I set Pressure, Density, Body Forces and Turbulent Viscosity Under relaxation factors in OF. ? THANK YOU to anyone that can answer any of these questions. ztnuaa likes this.   February 3, 2021, 02:04 #2
New Member

Ilhwan Yeo
Join Date: Jan 2020
Posts: 18
Rep Power: 5 Quote:
 Originally Posted by gentodin Hi all, I am trying to replicate the simulation from ANSYS fluent to OpenFOAM but I could not find some settings or do not know how to set them in OF.(This is my way of learning, feel free to drop comment for a better way). The following are the areas I am looking at fvSolution and fvScheme in the OF settings. Currently there are 4 segments of input parameters I divided them into and each contains question as shown below: 1) The fvSolution algorithm used was PISO Fluent settings: Skewness Correction 1 Neighbor Correction 1 OF settings: PIMPLE { nNonOrthogonalCorrectors 1 nCorrectors 1 nOuterCorrectors 1 } Questions: When the simulation is running in fluent, there is an additional option of setting max iteration per timestep, does this iteration refer to total no. of PISO loop per timestep or the control of other loops? 2) fvSchemes grad and div settings fluent settings: gradient, leastsquareCellBased Pressure, Second Order upwind Momentum, Second Order upwind TKE, Second Order upwind TDR, Second Order upwind Energy, Second Order upwind Transient Formulation, First Order implicit OF settings: ddtSchemes { default Euler; } gradSchemes { default none; grad(U) leastSquares; grad(T) leastSquares; grad(k) leastSquares; grad(epsilon) leastSquares; grad(R) leastSquares; } divSchemes { default none; div(phi,U) Gauss linearUpwind grad(U); div(phi,T) Gauss linearUpwind grad(T); div(phi,k) Gauss linearUpwind grad(k); div(phi,epsilon) Gauss linearUpwind grad(epsilon); div(phi,R) Gauss linearUpwind grad(R); div(R) Gauss linearUpwind grad(R); div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear uncorrected; } interpolationSchemes { default linear; } snGradSchemes { default uncorrected; } Questions: Are the laplacianSchemes/interpolationschemes in fluent follow the individual schemes that are present? i.e. momentum follows all second order upwind for div, laplacian and interpolation schemes. Why can't set linearUpwind for div((nuEff*dev2(T(grad(U))))) under divSchemes? 3) fvSolution Residuals All settings are the same except for continuity and pressure. Does anyone know where to set the Pressure residuals in fluent? Does anyone know where to set the continuity Residuals in OF? 4) fvSolution Under-Relaxation Factors Fluent settings: Pressure 0.3 Density 1 Body Forces 1 Momentum 0.7 TKE 0.8 TDR 0.8 Turbulent Viscosity 1 Energy 1 OF settings: Momentum 0.7 TKE 0.8 TDR 0.8 Question: How do I set Pressure, Density, Body Forces and Turbulent Viscosity Under relaxation factors in OF. ? THANK YOU to anyone that can answer any of these questions.

Did you solve this problem??   February 21, 2021, 20:56 Reply to this thread
#3
Member

Anonymous.
Join Date: Sep 2020
Posts: 35
Rep Power: 5 Quote:
 Originally Posted by jayson Did you solve this problem??
I manage to find out about the 1st question where the max iteration in ANSYS fluent is referring to max outer iterations per timestep as shown here:

For 4th question, setting pressure relaxation is simple typing this in fvSolution file in OF:

relaxationFactors
{
equations
{

p 0.3; //Pressure relaxation
pFinal 1;

U 0.7; //Velocity relaxation
UFinal 1;

}
}  Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post SAI_ OpenFOAM 0 November 21, 2018 13:33 CFDFoundation OpenFOAM Announcements from OpenFOAM Foundation 2 October 6, 2017 05:40 muhammss OpenFOAM Running, Solving & CFD 7 July 4, 2016 08:17 HaKu FLUENT 0 May 6, 2011 13:54 lr103476 OpenFOAM Running, Solving & CFD 40 December 18, 2008 09:09

All times are GMT -4. The time now is 07:27.