Problems in a two-phase VOF modeling
 

Hi guys,
I'm trying to set up a two-phase flow simulation in a square channel. The computational domain (also BCs) shows in the following fig..
http://ww1.sinaimg.cn/large/78514913jw1dr9sfmq7tlj.jpg
I wounder if there is any feasible way to mesh the whole domain using hexahedron grid. then, specify the green part as one fluid, and the rest part as the other. the two part are much like virtual volumes, so i do not need to mesh them separately. By doing this, the grids quality will be the best.
can any one give me some help/advise? thanks.

--lynghoo