Thank you, Kremell. nFor my first picture, I didn't use either one model. When I use either CSS or CSF, the parasitic current always exist and the water penetrate the interface and get into the air region. However, when I only set up a constant surface tension without these models, it works well. Thus, I wonder if it is necessary to enable one of the model to say modelling the surface tension. The guide seems to say that it is necessary so i am confused.nAlso, is what you mean the type of gird the shape of the mesh cell?.BestnJianhuan