[zhangweisnoopy]

Hi,all
I'm building a 2D simulation program for a two-phase incompressible viscous fluid simulation (water and air) with VOF method. The VOF method I use is the Hirt & Nichols SOLA-VOF scheme but the reconstruction method is PLIC (Young).
In a two-phase approach, when the air water interface is no longer considered as a free-surface, but the interface is still reconstructed using the VOF algorithm. The function Fs is used to determine the
aggregated density value inside a grid cell, using weighted
averaging .The incompressible Navier-Stokes equations without surface tension is solved with variable density and Viscosity considering water and gas.
The effective density and Viscosity are computed as
rho = rho_liquid*Fs+(1-Fs)*rho_gas
Fs is the fraction of the cell that is filled with fluid in VOF.

I use the MAC staggered meshes.So density and Viscosity at both cell center and face should be caculated. I ues the program to simulate the break dam over a dry bed ,but it doesn't work because the pressure possion equation isn't convergent after several hundreds steps...It seems that the interface is not accurate(I don't know it is the problem) ..I can figure it out .
Give some advise please,thanks very much!!