Optimal receptivity and roughness analyses for transition in high-speed boundary layers
Abstract
For hypersonic ballistic and reentry vehicles, aerodynamic forces and compressional heating must be carefully controlled, and the state of the aerodynamic boundary layer must therefore be predicted throughout the flight envelope. Predicting laminar-to-turbulent transition remains a pacing item, and, while much is understood about the basic mechanisms of instability in high-speed boundary layers, the enormous variety and stochastic nature of external disturbances and surface roughness that trigger instabilities presents an enormously complex and large parameter space. This daunting forward problem of determining the flow instabilities triggered by external disturbances is referred to as the receptivity problem. This project focuses on a far more efficient inverse receptivity problem that determines those realizable external disturbances that lead to the largest linear amplification in the nascent laminar boundary layer. We refer to this framework as optimal receptivity analysis. Previous optimization methods, often referred to as input-output analyses, were defined by bounding the growth achievable for a much larger input space that includes disturbances that are not physically realizable. In this work, we build on our recently proposed methodology that seeks to build bases for physically realizable incident disturbances and to find those combinations of real disturbances that trigger maximal amplification. We extend our previous framework to include the important effect of the scattering of disturbances through the shock and shock layer, and their interaction with surface roughness. To render optimal receptivity analysis computationally tractable for realistic, complex geometries of interest to the US Navy, we will also implement two recently discovered schemes that are designed to accelerate the associated linear algebra. The proposed approach thus unifies both free-stream receptivity and non-smooth walls into a common framework that is amenable to realizable input-output analysis. The formulation allows receptivity and roughness to be considered both in concert and in isolation, and such information will lead to improved physical understanding of the ways in which roughness triggers boundary layer transition.Approved for Public Release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512072
Entities
People
- Tim Colonius
Organizations
- California Institute of Technology
- Office of Naval Research
- United States Navy