Supersonic aerodynamics

Supersonic aerodynamic problems are those involving flow speeds greater than the speed of sound. Calculating the lift on the Concorde can be an example of a supersonic aerodynamic problem.

Supersonic flow behaves very differently from subsonic flow. The speed of sound can be considered the fastest speed that "information" can travel in the flow. Gas travelling at subsonic speed diverts around a body before striking it, it can be said to "know" that the body is there. Air cannot divert around a body when it is travelling at supersonic speeds. It continues to travel in a straight line until it reaches a shock wave and decelerates to subsonic speeds. Mathematically, supersonic flow is described by a hyperbolic partial differential equation while subsonic flow is described by an elliptic partial differential equation.

Another example of the difference between supersonic and subsonic flow is the behaviour in a convergent duct (known as a nozzle in subsonic flow and a diffuser in supersonic flow). Subsonic flow in a convergent duct accelerates and supersonic flow decelerates.