Check out our latest research paper, discussing the Mach Independence of entropy layer instabilities in hypersonic flight.
When studying transition to turbulence in hypersonic flows, it is extremely challenging to relate the results at different Mach numbers. The current theoretical work offers a step in this direction by proposing a way to relate entropy layer instabilities across a range of Mach numbers. The theoretical findings may be particularly useful for relating experimental results at different Mach numbers.
The proposed methodology to relate beween entropy layer instabilities at various Mach numbers relies on proper normalization, inspired by the work of Oswatitsch, leading to Mach independence for very large Mach numbers. In addition, normalization by a representative thickness of the entropy layer leads to a much earlier onset of the Mach indepdence, for freestream Mach numbers as small as 5.