Observations of Traveling Crossflow Resonant Triad Interactions on a Swept Wing

Abstract

Experimental evidence indicates the presence of a triad resonance interaction between traveling crossflow modes in a swept wing flow. Results indicate that this interaction occurs when the stationary and traveling crossflow modes have similar and relatively low amplitudes (~1% to 6% of the total freestream velocity). The resonant interaction occurs at instability amplitudes well below those typically known to cause transition, yet transition is observed to occur just downstream of the resonance. In each case, two primary linearly unstable traveling crossflow modes are nonlinearly coupled to a higher frequency linearly stable mode at the sum of their frequencies. The higher-frequency mode is linearly stable and presumed to exist as a consequence of the interaction of the two primary modes. Autoand cross-bicoherence are used to determine the extent of phase-matching between the modes, and wavenumber matching confirms the triad resonant nature of the interaction.

Traveling Crossflow Instability for HIFiRE-5 in a Quiet Hypersonic Wind Tunnel

“…36,[38][39][40] Saric and Reed 35 detail the pertinence of nonlinear effects when predicting crossflow instability growth and transition for incompressible flow. It has been well established that stationary modes, after a period of linear growth, saturate nonlinearly and give rise to secondary instabilities that then rapidly lead to transition (see, for instance, Reference 41).…”

Freestream Effects on Boundary Layer Disturbances for HIFiRE-5

“…6 Considerable study has been made of crossflow instabilities for incompressible flows. [5][6][7][8][9][10][11] It has been established that stationary modes undergo a period of linear growth, saturate nonlinearly, and then develop secondary instabilities that rapidly lead to transition. 5,9 The majority of historic crossflow research has focused on stationary modes, since this is expected to be the dominant crossflow instability in the lownoise flight environment.…”

Simultaneous Infrared and Pressure Measurements of Crossflow Instability Modes for HIFiRE-5

“…4 Considerable study has been made of crossflow instabilities for incompressible flows. [3][4][5][6][7][8][9] It has been established that stationary modes undergo a period of linear growth, saturate nonlinearly, and then develop secondary instabilities that rapidly lead to transition. 3,7 The majority of historic crossflow research has focused on stationary modes, since this is expected to be the dominant crossflow instability in the lownoise flight environment.…”