Numerical Investigation of Nonlinear Transition Stages in Hypersonic Boundary Layers for Wind Tunnel and Free Flight Conditions
Abstract
From our previous research funded by AFOSR, we found conclusive evidence that compressibility effects can cause a considerable stretching of the nonlinear transition regime in the downstream direction compared to incompressible boundary layers. The practically relevant implication of this finding is that nonlinear transitional flow fields can cover very large downstream extents of actual hypersonic flight vehicles. For the conditions of the "quiet" Mach 6 tunnel at Purdue University, the nonlinear interactions in the transition regime can lead to the development of streamwise streaks of locally very high skin friction and heat loads (“hot streaks”) that far exceed the turbulent values. This may negatively affect the aerodynamic performance and may compromise the structural integrity of flight vehicles. Therefore, a comprehensive research effort is proposed to investigate the fundamental physics in the nonlinear stages of hypersonic boundary layer transition for a variety of ground test and free flight conditions. The main investigative tools for the proposed research are Direct Numerical Simulations (DNS) based on the complete Navier Stokes equations. The main focus is on exploring if and how the different tunnel conditions and test articles (models) of other hypersonic ground tests and free flight experiments affect the nonlinear transition physics. Answers to these questions are of utmost importance for hypersonic flight as no ground facilities existing today can match simultaneously all parameters for typical free flight conditions. Particular emphasis will be also on the effects of the free stream disturbance environment on the nonlinear stages and breakdown. As a consequence, the receptivity mechanisms relevant for the various wind tunnels will be investigated with respect to both the primary and the secondary instabilities and beyond.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501910208
Entities
People
- Hermann Fasel
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Arizona