[bieshuxuhe]

hello!

" Water waves create vortices on the air-side of the free surface. These vortices have high velocity, impact the Courant number, push the time step to be smaller, and increase the simulation costs. For many problems, stresses generated on air side are negligible. Solution: ignore convective term on air-side. " said by Eric Paterson in 3rd OpenFoam Workshop.

Eric Paterson proposed a similar and effective solution to the problem of high air velocity above the free surface .He modifies air convection in the transport equation by multiplying the phase fraction value to the convective term. In this manner convection is kept intact for those parts of the computational cells with the phase fraction value of 1, and reduced for region with lower phase fraction value accordingly!

then , i modify the "UEqn.H" in the interFoam as following (note the red colour) :
fvVectorMatrix UEqn
(
fvm::ddt(rho, U)
+ alpha1*fvm::div(rhoPhi, U)
+ turbulence->divDevRhoReff(rho, U)
);

and after wmake , i began to run the "interFoam/laminar/damBreak" case without any modification . but i found the time step is getting smaller and smaller ! at last , the deltaT is about "1.0e-10" s.
the modification i did in "UEqn.H" should not produce results like that ! it is counterproductive !

is there something wrong with my operation?
could you help me ?
thanks.