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Numerical solution parameters
- Numerical solution parameters are stored in directory system
- In file fvSolution there are stored parameters for solving system of linear equations and parameters for numerical method
- Print file fvSolution on the screen:
# cat $FOAM_RUN /pitzDaily/system/fvSolutionsolvers { p { solver GAMG; tolerance 1e-06; relTol 0.1; smoother GaussSeidel; } "(U|k|epsilon|omega|f|v2)" { solver smoothSolver; smoother symGaussSeidel; tolerance 1e-05; relTol 0.1; } } - Section solvers defines which linear system solvers are used to compute quantities (partial differential equations are transformed to system of linear equations)
- Each quantity has its options
- Parameter solver defines which solver is used
- Parameter preconditioner (not used in this case) defines preconditioner of linear system solver
- Parameter relTol defines relative tolerance of linear system solver (order of residual decrease for each iteration)
- Parameter tolerance defines absolute tolerance of linear system solver (initial residual is checked)
- Overview of linear solvers
- Overview of preconditioners
- “Smoother“ overview
Definition “Smoother“ DIC Diagonal Incomplete Cholesky (symmetric) GaussSeidel Gauss-Seidel iteration method DICGaussSeidel combination of DIC and GaussSeidel SIMPLE { nNonOrthogonalCorrectors 0; consistent yes; residualControl { p 1e-2; U 1e-3; "(k|epsilon|omega|f|v2)" 1e-3; } } - In section SIMPLE there are defined parameters of SIMPLE algorithm and convergence criteria residualControl
- Parameter nNonOrthogonalCorrectors defines number of non-orthogonal correctors (may improve convergence on non-orthogonal meshes) (0 orthogonal mesh – 20 strongly non-orthogonal mesh)
- If all quantities reach residuals in section residuaControl, computation is stopped
relaxationFactors { equations { U 0.9; // 0.9 is more stable but 0.95 more convergent ".*" 0.9; // 0.9 is more stable but 0.95 more convergent } } - In section relaxationFactors there are defined relaxation factors for individual quantities
- In file fvSchemes there are stored numerical schemes properties for individual quantities
- Print file on the screen:
# cat $FOAM_RUN /pitzDaily/system/fvSchemesddtSchemes { default steadyState; } - In section ddtSchemes there are defined schemes for time derivatives
gradSchemes { default Gauss linear; } - In section gradSchemes are defined schemes for gradient discretization
- There may be defined different schemes for each quantity
divSchemes { default none; div(phi,U) bounded Gauss linearUpwind grad(U); div(phi,k) bounded Gauss limitedLinear 1; div(phi,epsilon) bounded Gauss limitedLinear 1; div(phi,omega) bounded Gauss limitedLinear 1; div(phi,v2) bounded Gauss limitedLinear 1; div((nuEff*dev2(T(grad(U))))) Gauss linear; div(nonlinearStress) Gauss linear; } - In section divSchemes there are defined schemes for divergence discretization
- There may be defined different schemes for each quantity
laplacianSchemes { default Gauss linear corrected; } - In section laplacianSchemes there are defined schemes for Laplace operator discretization
- There may be defined different schemes for each quantity
interpolationSchemes { default linear; } - In section interpolationSchemes there are defined schemes for interpolating from cell centers to cell faces
- There may be defined different schemes for each quantity
snGradSchemes { default corrected; } - In section snGradSchemes there are defined schemes for gradient discretization in direction perpendicular to the boundary
- There may be defined different schemes for each quantity
wallDist { method meshWave; } // ************************************************************************* // - In section wallDist there is method for calculation of distance of cell centers and boundary (which is needed in turbulent models).
- More information is in the web documentation:
http://www.openfoam.com/docs/user/fvSchemes.php