Question

Boundary condition V.n = 0 is applied at the surface to non dimensionlize the governing equations when fluid is being transferred.

(a) True

(b) False

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Query is from Mach Number Independence in section Transonic and Hypersonic Flows of Aerodynamics

Answer 1

Right choice is (b) False

The explanation: When there is no fluid transfer taking place between the surface, then in order to non dimensionalising the governing equations, we use the boundary condition V.n = 0. But, when there is transfer of fluid in or out of the surface then normal velocity vT has to be incorporated thus altering the boundary condition as V.n = vT.