What are the general boundary conditions for nonviscous, incompressible fluid flow? I am trying to find the velocity of fluid at the surface of a sphere with the incident fluid having uniform velocity. I am surprised to find in the solution that the radial velocity at the surface does not vanish. For magnetostatics, div B = 0 implies B-perp is continuous. Would not div v= 0 imply the same for v-perp? What about the same problem but incident upon an infinite plane? Would the velocity not vanish at the surface?