Question

Which boundary condition applied at the surface to non dimensionlize the governing equations?

(a) V.n = 0

(b) V × n = 0

(c) V.(V × n) = 0

(d) V × (V × n) = 0

I got this question in final exam.

My question is based upon Mach Number Independence in division Transonic and Hypersonic Flows of Aerodynamics

Answer 1

Correct choice is (a) V.n = 0

For explanation: While non dimensionalising the governing equations for steady inviscid flow, the boundary condition applied is that the flow of tangent to the surface. This means that if V is the velocity vector and n is the unit normal vector at the surface, then for the flow to be tangent, V.n = 0.