Question

If the Riemann variants are known, how can we compute the mass – motion velocity u?

(a) \(\frac {J_++J_-}{2}\)

(b) \(\frac {J_+-J_-}{2}\)

(c) \(\frac {J_+×J_-}{3}\)

(d) \(\frac {J_+×J_-}{6}\)

I have been asked this question during an interview.

Question is from Finite Waves in chapter Unsteady Wave Motion of Aerodynamics

Answer 1

Correct option is (a) \(\frac {J_++J_-}{2}\)

To elaborate: On solving the two Riemann invariants J+ and J– for the two characteristic lines passing through a point x, y in an x – y plane, we get the solution for mass – motion velocity u. It is given by:

u = \(\frac {J_++J_-}{2}\)