Supersonic flow

Summary

A supersonic flow is a compressible flow in which the fluid moves faster than the local speed of sound. So its Mach number exceeds $1$. Small disturbances cannot travel upstream in such a flow: they stay inside a cone downstream of their source. Its steady equations are hyperbolic, so they are solved by marching downstream, for instance with the method of characteristics. Shock waves and expansion fans are its typical features, and it governs the design of supersonic aircraft, rockets and wind tunnels.