Question

The definition of flow being compressible is______

(a) M > 0.3

(b) M > 0.5

(c) Depends on precision required

(d) Another name for supersonic flows

This question was posed to me in final exam.

I would like to ask this question from Flow Compressible topic in portion Normal Shock Waves of Aerodynamics

Answer 1

The correct option is (a) M > 0.3

The explanation: For the subsonic flows, it depends on the matter of accuracy whether to treat a flow as compressible or not. For supersonic flows it is always compressible. In general, M > 0.3 can be regarded as compressible flow.