The Surface Friction and the Flow over Mountain

The flow over mountain is quite complicated. There are a lot of papers on this problem and a lot of progresses have been made. However, in the most of these papers, just the dynamics contributions of mountain have been ana-lysed; the effect of the friction is often neglected. Since the frictional effect is always associated with flow, especially when it flows over the mountain. The study shows that the friction is small in the magnitude but it is not a negligible effect because it changes the features of the flow. In the case of super-or sub-critical flow, there are two extremes: one maximum, one minimum of the fluid surface on the lee-side of the mountain, while in the inviscid fluid, there is just one extreme. The frictional effect should neither be too strong nor too weak to make the situation happened ac-cording to the investigation of this paper.