Aerodynamic Heating in Hypersonic Boundary Layers:\ Role of Dilatational Waves

TL;DR

This study investigates how dilatational waves in hypersonic boundary layers cause localized intense aerodynamic heating, combining experiments and simulations to understand the temperature distribution during transition.

Contribution

It provides new insights into the role of second-mode dilatational waves in aerodynamic heating through combined experimental and computational analysis.

Findings

Dilatational waves cause localized high-frequency compression and expansion.

Surface temperature overshoot occurs due to intense heating by these waves.

Temperature decreases gradually after wave decay as transition completes.

Abstract

The evolution of multi-mode instabilities in a hypersonic boundary layer and their effects on aerodynamic heating are investigated. Experiments are conducted in a Mach 6 wind tunnel using Rayleigh-scattering flow visualization, fast-response pressure sensors, fluorescent temperature-sensitive paint (TSP), and particle image velocimetry (PIV). Calculations are also performed based on both parabolized stability equations (PSE) and direct numerical simulations (DNS). It is found that second-mode dilatational waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region that rapidly heats the fluid passing through it. As a result, the surface temperature rapidly increases and results in an overshoot over the nominal transitional value. When the dilatation waves decay downstream, the surface temperature decreases gradually until transition is completed. A theoretical analysis is provided to interpret the temperature distribution affected by the aerodynamic heating.