Global stability and sensitivity analysis of a hypersonic slender cone
Abstract
Hypersonic flows are characterized by rich physics which open new avenues for transition to turbulence that are ineffective at lower speeds. Elevated heat transferrates towards the wall in the turbulent flow past the point of transition form one of the main obstacles to the large-scale deployment of hypersonic capabilities. The proposed study will advance the state of the art in high-speed transition research through the global analysis of growth and receptivity mechanisms in a realistic geometry described by a sharp cone with 7-degree half-angle at zero angle of attack. The considered free-stream speed, Ma=6, leads to the formation of an attached oblique shock which is captured in the computational domain of the global analysis. Thedirect incorporation of shock waves describes a major advancement over existing approaches which either ignored shocks or represented them indirectly throughboundary conditions.The present study will address the full extent of the transition process, starting from the initial receptivity stage during which external disturbances initiate a perturbation field inside the boundary layer. In contrast to earlier empirical surveys based on parameter studies, the analysis will rigorously address the hypersonic receptivity process by incorporating information provided by the adjoint governing equations.Past the receptivity stage, the transition process advances through the exponential oralgebraic amplification of perturbations inside the near-wall shear. The global analysis will directly capture the underlying physics of exponential flow instabilities,such as inviscid Mack modes, and their potential interactions with shock waves without relying on assumptions of weakly non-parallel flow. In addition, the algebraic growth mechanisms which lead to the streaks associated with bypass transition will beinvestigated through a transient growth analysis. The present work will thus provide the first global analysis of the mechanisms underlying both natural and bypasstransition while accounting for the complex geometry of the cone as well as the presence of shocks. In a final setup, paths towards controlling and preventingbreakdown to turbulence will be investigated in a structural sensitivity analysis which again utilizes information provided by the linear adjoint operator. The approach presents a fundamental improvement to the present state of hypersonic transition research by directly computing the spatial structure of modifications to the flow, for instance due to geometry changes, which result in reduced amplification of instabilities and thus delay breakdown to turbulence. The linear analyses will be accompanied by fully resolved direct numerical simulations to study the nonlinear late stages of breakdown to turbulence. The knowledge gained in the project will provide the fundamental knowledge needed in the development of more accurate transitionmodels and design tools as well as in the conception of more effective strategies for delaying transition in the flow around hypersonic vehicles.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712341
Entities
People
- Parviz Moin
Organizations
- Office of Naval Research
- Stanford University
- United States Navy