Abstract
The evolution of the first- and second-mode instabilities in a hypersonic flat plate boundary layer is investigated. Experiments are conducted in a Mach 6.5 quiet wind tunnel using particle image velocimetry, Rayleigh-scattering flow visualization, and schlieren methods. Glow discharge is introduced as an artificial disturbance. The results show that an artificially introduced disturbance in the first-mode frequency range can excite a specific second-mode wave that is one of the high-order harmonics of the added disturbance. For the first time, we find a clear harmonic relationship between the first- and second-mode waves, as well as the phase lock phenomenon between them.
Highlights
The study of transition under hypersonic conditions has increasingly become an attractive research topic
Hypersonic boundary layer transitions at low disturbance levels are caused by various flow instabilities, among which the first mode and the second mode are the most basic and important
Kosinov et al.12 and Maslov et al.13 first developed a glow-discharge method as an artificial disturbance to study how the boundary layer develops in supersonic and hypersonic flows
Summary
The study of transition under hypersonic conditions has increasingly become an attractive research topic. We report an experimental study of the first and second modes in a hypersonic flat plate boundary layer.
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