Real gas effects on sound radiation by unstable modes in hypersonic boundary layers
Abstract
The proposed project is motivated by recent theoretical and DNS findings that the ~supersonic~second Mack modes in hypersonic boundary layers become synchronized with slow acousticmodes. The synchronization indicates that there is a possibility of coupling between the unstablediscrete modes and the slow acoustic perturbations, and such coupling leads to sound radiation.This idea was confirmed by recent DNS results which show that wave packets of ~supersonic~Mack modes do emit acoustic waves as predicted by theoretical estimates. The crucial point ofthese new findings is that the sound radiation by wave packets of ~supersonic~ second Mackmodes changes their dynamics and leads to a reduction of wave amplitudes, or the stabilizationof the Mack modes. This effect may have important engineering applications by delaying thetransition onset. The new findings, however, were only based on a calorically perfect gas modeland the assumption that the wall temperature is lower than temperature in free stream. The PI~srecent results including the real gas effects show that the structure of the second mode spectracan be very different from those of calorically perfect gas flow. As a result, the effects of soundradiation might be significantly changed by the real gas effects. Therefore, the objective of theproposed project is to investigate and elucidate the role of the real gas effects on the soundradiation of the supersonic Mach modes and the transition onset. The problem is related to thefeasibility of the ~e-to-N~ method for transition prediction, which does not take into account theenergy transfer from wave packets of second Mack modes to acoustic radiation. The problemwill be studied by two concurrent and collaborative approaches: theoretical analysis by Tumin atthe University of Arizona and direct numerical simulations by Zhong at UCLA. Proposed testcases include high enthalpy flows in high-speed flight conditions with the real gas effects andhypervelocity flow conditions used in T5 wind tunnel tests at Caltech.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 03, 2017
- Source ID
- N000141712343
Entities
People
- Anatoli Tumin
Organizations
- Office of Naval Research
- United States Navy
- University of Arizona