- **OpenFOAM**
(*https://www.cfd-online.com/Forums/openfoam/*)

- - **Algebraic Model for Variance - grid size surface field**
(*https://www.cfd-online.com/Forums/openfoam/103868-algebraic-model-variance-grid-size-surface-field.html*)

Algebraic Model for Variance - grid size surface fieldHello,
I have a rhoPimpleFoam solver which solve the equation for an extra scalar equation c (progress variable) and an algebraic equation for its variance. The model for the variance is var (c) = a * (Delta X)^2 * (grad (c))^2 where the Delta X is the grid size, a is a constant (0.08333) and grad (c) is the gradient of C field. The solver upload the data for progress variable (which goes from 0 to 1) and variance (which goes from 0 to 0.25) from a two dimensional table . Table looks like: Variance PV other variables 0 0 : : : 1 0.1 0 : : : 1 0.5 0 : : : 1 -------------------------------- My questions are the following: 1) I defined the grid size field in the following way and I would like to know if it's correct surfaceScalarField GridSize ( IOobject ( "GridSize", runTime.timeName(), mesh, IOobject::NO_READ, IOobject::NO_WRITE ), mesh, dimensionSet(0,-1,0,0,0,0,0) ); GridSize = mesh.surfaceInterpolation::deltaCoeffs(); ---------- 2) My secondo question is: considering the equation for the variance: VarC.internalField() = pow((GridSize.internalField(),2)*0.08333*magSqr(fv c::grad(C)); when I run the simulation, after a few iterations, the variance goes out of bound (despite I impose to stay inside the limit of 0-0.25) and the simulation crashes soon. Is that have something to do with the gridsize definition? thanks for the help |

All times are GMT -4. The time now is 13:18. |