The problem of classical (compressible)fluids passing an obstacle was well-known and studied by many. Roughly speaking, when the velocity of the fluid is small, the flow would be smooth and nothing much would occur(subsonic region). When the fluid velocity is very large, there are shocks and the fluids become rather turbulent and mathematically it is hard to describe (supersonic). In between, there is a critical speed (far away) at which the fluid reach the maximum speed (sound speed for the fluid) at the boundary of the obstacle. Since a superfluid by the definition is frictionless, hence it would not develop shocks. On the other hand, formal arguments imply that the long-wave approximations of superfluid flows (semiclassical limits) would be a classical flow described by the compressible Euler equations. The latter may develop shocks however. A natural question is: how would one explain superfluid flows then? Reasonings from physics which were also supported by various numerical simulations lead to the so-called vortex nucleations. The aim of this talk is to present a recent joint work with Jun-Cheng Wei on this problem.