Growth and breakdown of a wave packet into a turbulent spot in a cone boundary layer at mach 6 jayahar sivasubramanian1

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1 Scopus citations

Abstract

Direct Numerical Simulations are performed to investigate the growth and breakdown of a wave packet into a turbulent spot in a sharp cone boundary layer at Mach 6. In order to understand the natural transition process in hypersonic cone boundary layers, the flow was forced by a short-duration (localized) pulse. The pulse disturbance developed into a three-dimensional wave packet which consisted of a wide range of disturbance frequencies and wave numbers. The flow parameters for the simulations are based on the experimental conditions of the Boeing/AFOSR Mach 6 quiet-flow Ludwieg Tube at Purdue University. First, the linear development of the wave packet was studied by forcing the flow with a low-amplitude pulse (0.001% of the free-stream velocity). The dominant waves within the resulting wave packet were identified as the second-mode two-dimensional disturbance waves. In addition, weaker first-mode oblique waves were also observed on the lateral sides of the wave packet. In order to investigate the weakly nonlinear transition regime, medium-amplitude pulse disturbances (0.5% of the free-stream velocity) were introduced. The response of the flow to the medium-amplitude pulse disturbances indicated the presence of a fundamental resonance mechanism. Lower secondary peaks in the disturbance wave spectrum were identified at approximately half the frequency of the high-amplitude frequency band, which would be an indication of a subharmonic resonance mechanism. Strong peaks were also observed for low-wave-number second-mode oblique waves, which indicate a possible presence of an oblique breakdown mechanism. Finally, in order to identify more clearly which of these mechanisms ultimately leads to turbulent breakdown, a simulation with a higher forcing amplitude (5% of the free-stream velocity) was performed. The resulting strongly nonlinear wave packet eventually leads to localized patches of turbulent flow (turbulent spots). The disturbance wave spectrum indicates that both second-mode fundamental resonance and oblique breakdown mechanisms may be the dominant mechanisms for the investigated flow. Both mechanisms may play a role in the natural transition process for a cone boundary layer at Mach 6.

Original languageEnglish (US)
StatePublished - Dec 1 2012
Event50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition - Nashville, TN, United States
Duration: Jan 9 2012Jan 12 2012

Other

Other50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition
CountryUnited States
CityNashville, TN
Period1/9/121/12/12

ASJC Scopus subject areas

  • Aerospace Engineering

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    Fasel, H. F. (2012). Growth and breakdown of a wave packet into a turbulent spot in a cone boundary layer at mach 6 jayahar sivasubramanian1. Paper presented at 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Nashville, TN, United States.