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Optical Measurements of Nonlinear Mack Mode Interactions on a Cooled Flared Cone in Quiet Mach 6 Flow

AIAA 2024-2188
Session: Instability and Transition VII
Published Online:

Multi-point focused laser differential interferometry (FLDI) is used to study the nonlinear interactions of the second mode on a 91-6 flared cone model with two different wall temperature conditions. The multi-point measurements are used with higher-order spectral analysis, namely a cross-bicoherence analysis, to understand the impact that wall temperature has on frequency summing and frequency difference interactions responsible for harmonic generation and eventual broadband turbulence generation. Results from the analysis shows that the cross-bicoherence has sensitivity to wall temperature and shows that the cooler wall condition corresponds to earlier transition. Furthermore, comparing cross-bicoherence results to intermittency results suggests an anti-correlated relationship, implying that energy from second-mode associated fluctuations feeds into broadband turbulent fluctuations as the transition process progresses to full turbulent breakdown.