[Kareem Abdelshafy]

Hello Foamers;

I have problem running a modified version of interfoam (I am using phase field method instead of VOF) in parallel. The program run nicely in parallel, if I put zero velocity boundary conditions. However, if I put non zero shear velocity B.C in the top B.C, the pressure corrector does not converge and after several time steps, a checkboard appears in the pressure (see below). The same program run nicely in serial in all cases.
The program solves for two fluid with low Reynolds numbers and high viscosity ratio. fluid 1 has Re = 1e-3 and fluid 2 has Re = 1e-9. I am setting the momentum predictor to yes, and ncorrector to 50! which was necessairly to make the serial version converge. Usually the initial residual for pd reaches below 1e-5 in serial version. In the parallel version (with external shear velocity in the B.C), the initial residual of pd never reaches below 5e-5(keeping oscillating around this number in every ncorrector iteration) and increases with time untill the checkboard pressurer appears and the results blow up.
I am using PISO with no relaxation, the mesh is (256 X 256) simple squares. I tried several linear solvers for pd including the PCG with preconditioned GAMG and GAMG with DIC or DICGaussSeidel smoother , but nothing solved the problem. I am using foam-extend 3.2 because I need block coupled solver. Any suggestion is appreciated. Thanksinterfoam checkboard.png