Nonlinear Growth and Breakdown of the Hypersonic Crossflow Instability
Abstract
A sharp, circular 7 half-angle cone was tested in the Boeing/AFOSR Mach-6 Quiet Tunnel at 6 angle of attack, extending several previous experiments on the growth and breakdown of stationary crossflow instabilities in the boundary layer. Measurements were made using infrared imaging and surface pressure sensors. Detailed measurements of the stationary and traveling crossflow vortices, as well as various secondary instability modes, were collected over a large region of the cone. The nonlinear breakdown mechanism induced by each type of roughness appears to be different. When using the discrete RIM roughness, the dominant mechanism seems to be the modulated second mode, which is significantly destabilized by the large stationary vortices. There is no evidence of the presence of traveling crossflow when using the RIM roughness, though surface measurements cannot provide a complete picture. The modulated second mode shows strong nonlinearity and harmonic development just prior to breakdown. In addition, pairs of hot streaks merge together within a constant azimuthal band, leading to a peak in the heating simultaneously with the peak amplitude of the measured secondary instability. The heating then decays before rising again to turbulent levels. When using the distributed roughness there are several differences in the nonlinear breakdownbehavior. The hot streaks appear to be much more uniform and form at a higher wavenumber, which is expected given computational results. Furthermore, the traveling crossflow waves become very prominent in the surface pressure fluctuations and weakly nonlinear. In addition there appears in the spectra a higher-frequency peak which is hypothesized to be a type-I secondary instabilityunder the upwelling of the stationary vortices. The traveling crossflow and the secondary instability interact nonlinearly prior to breakdown.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2019
- Accession Number
- AD1181456
Entities
People
- Joshua B. Edelman
Organizations
- Purdue University