[kk415]

Hello All,


I was trying to include an artificial viscosity term in the momentum equation. Doing so I realized that momentum equation written in Ueqn.H is consistent with the dynamic viscosity and not the kinematic viscosity. But we gave the input in transport property as kinematic viscosity. So is it really the correct way ?


My piece of code:


art_mu=runTime.deltaT()*sigma*mag(fvc::grad(Hs));

MRF.correctBoundaryVelocity(U);

fvVectorMatrix UEqn
(
fvm::ddt(rho, U) + fvm::div(rhoPhi, U) - fvm::laplacian(art_mu, U)
+ MRF.DDt(rho, U)
+ turbulence->divDevRhoReff(rho, U)
==
fvOptions(rho, U)
);


So If I try to include art_nu by dividing by rho then it say error of dimensions. Am I doing it correct way ? Are my interpretation correct?

[Tobi]

Hi,


a) please use code tags so that we can read you code snippet more properly
b) we provide the kinematic viscosity and the density. Thus we can recalc the "constant" dynamic viscosity
c) the following function:

+ turbulence->divDevRhoReff(rho, U)

is doing everything for you. If you need to know how this function works, you can either check out the source code or the information given in my book.


divDevRhoReff = divergence of the deviatoric part of the Reynolds Stress tensor = shear rate tensor (:
If you want to use your code, you need to remove the turbulence-> function and further:


a) you do not take care about turbulent increase of mu
b) you do not have stabilization terms included
c) thus, your equation is not as stable as the one provided by FOAM directly