Instability and Transition Experiments in the Boeing/AFOSR Mach 6 Quiet Tunnel

Nonlinear Evolution and Breakdown of Azimuthally Compact Crossflow Vortex Pattern over a Yawed Cone

“…Computations of secondary instability of crossflow modes in a hypersonic boundary layer were first reported by Li et al 29 The predicted secondary instabilities with the highest growth rates had frequencies that were comparable to those measured in the experiments at the Technical University of Braunschweig 20 and the Purdue University, [21][22][23] but the computations had also revealed the existence of less unstable modes with lower disturbance frequencies that were comparable to those measured by Craig and Saric. 25 Recently, more detailed secondary instability analyses for large amplitude stationary crossflow vortices over the yawed cone were described by Li et al 30,31 and Moyes et al 32 These works identified three major types of instability modes: those that originate from low-frequency traveling crossflow modes and high-frequency Mack mode instabilities of the unperturbed boundary layer, but get modulated (and potentially further destabilized) by the presence of large amplitude stationary crossflow vortices; and genuine, high-frequency secondary instability modes that arise entirely due to the presence of large amplitude stationary crossflow vortices and are concentrated in the shear layer that bounds those vortices.…”

“…However, measurements of crossflow instability in low-speed boundary layers have exposed the shortcomings of applying purely linear predictive models to transition in 3D boundary layers by revealing the importance of nonlinear effects during crossflow dominated transition. 3 The canonical configuration of a circular cone at angle of attack (AOA) includes the necessary elements to study both mixed mode transition and crossflow development in the context of both supersonic [4][5][6][7][8][9][10][11][12] and hypersonic [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] boundary-layer flows. Instability mechanisms for the boundary-layer flow over an elliptic cone have been investigated in Refs.…”

“…Experimental measurements of traveling crossflow instability on an elliptic cone 47 have yielded encouraging comparison with the linear stability predictions by Li et al 19 Measurements of crossflow instability over a yawed circular cone in three different Mach 6 wind tunnels have been reported in Refs. [20][21][22][23][24][25]. Besides a low frequency peak between 15 to 60 kHz that is presumably related to traveling crossflow disturbances, the circular cone measurements from Refs.…”

“…Besides a low frequency peak between 15 to 60 kHz that is presumably related to traveling crossflow disturbances, the circular cone measurements from Refs. [20][21][22][23] indicate higher frequency peaks, particularly in the vicinity of 300 to 350 kHz. Measurements by Craig and Saric [24][25] revealed lower frequency disturbances near 110 kHz that were still higher than the traveling crossflow disturbances of the unperturbed boundary layer.…”