Discussion Forum

Hello
Recently i have been trying to solve such a problem: how to couple free flow and Darcy flow for two phase fluid by Comsol in other to simulate the real situation of fluid flow freely near the permeable wall. I tryed to simulate the free flow (between two planes or in a pipe, etc) by phase field model and Darcy flow by two phase Darcy model. In the interface of the two models, we have to set three conditions: (1)tangential stress by using Beavior-Joseph-Saffman(BJS) boundary condition; (2)equal pressure; (3)equal velocity field. We can add the BJS condition by correcting the weak expression of Inlet pressure, no viscous stress. But how to constrain the equal pressure and velocity? By weak constraint, too? And how to solve the coulpling models is another problem. I want to solve it segregatedly. First solve the phase field model with the pressure constraint in the interface to get all other parameters like velocity and phase field variale. Then use the velocity obtained as the interface condition of Darcy model and to solve Darcy model to get a new pressure. Then go back to the first step to get the solution of the next time step. I know segregated solver will be a good choice. But does it solve the problem as the above sequence? I don't understand this solver's real theory. Thanks a lot if anyone can help me! It has perplexed me so long.

Thanks
Gao Bo