I read some paper, in the old version of COMSOL, we can choose a Mixed boundary condition (mix of Dirichlet, Newman and Cauchy conditions). in order to automatically transfer the boundary condition form pressure head to Flux, or Flux to pressure head.
But in the new version of COMSOL 4.2 or 4.3, I can not found that kind of setting,we would like to know how to switch the boundary condition from flux to pressure head during the calculation. We started from a flux boundary for rainfall infiltration (with negative pressure head), and when the pressure head at the surface boundary becomes positive, we would like to swith it to the pressure head boundary. We have no idea how to implement it in COMSOL4.3(Richards’Equation).
Could any expert have some suggestion? I appreciate for your help.
But in the new version of COMSOL 4.2 or 4.3, I can not found that kind of setting,we would like to know how to switch the boundary condition from flux to pressure head during the calculation. We started from a flux boundary for rainfall infiltration (with negative pressure head), and when the pressure head at the surface boundary becomes positive, we would like to swith it to the pressure head boundary. We have no idea how to implement it in COMSOL4.3(Richards’Equation).
Could any expert have some suggestion? I appreciate for your help.