Center for Environmental and Applied Fluid Mechanics Virtual Seminar: Christoph Brehm

Description

Christoph Brehm, assistant professor of mechanical engineering at the University of Kentucky, will give a talk entitled "Simulations of Particulate-Induced Transition in High-Speed Boundary-Layer Flows" for the Center for Environmental and Applied Fluid Mechanics. Tamer Zaki, associate professor of Mechanical Engineering at Johns Hopkins University, will host.

Please attend the event by using the Zoom link.

Abstract:

Various types of particulates with different origins are present in the stratosphere and the role they play in the free-flight boundary layer transition process is not well understood. Atmospheric particulates impinging on the surface of high-speed vehicles trigger disturbances inside the boundary layer which evolve into wavepackets and through exponential growth can provide a path to turbulence. This talk will present particulate-induced transition simulation results for flow conditions relevant to high-speed flight through the atmosphere.

In the first part of the presentation, a newly developed wavepacket tracking strategy coupled with a particle model will be presented. The wavepacket tracking approach, namely AMR-WPT (adaptive mesh refinement wavepacket tracking), relies on (1) the nonlinear disturbance flow formulation of the compressible Navier-Stokes equations, (2) a dual mesh overset approach, and (3) adaptive mesh refinement. The accuracy and efficiency of the AMR-WPT approach has been demonstrated for a wide range of transition mechanisms, e.g., receptivity, first and second mode, and cross-flow instabilities for 2-D and 3-D baseflows. To model particulate-induced transition, AMR-WPT was initially coupled with a particle solver based on the particle-in-cell approach. The second part of this talk will present a higher-fidelity simulation approach where the particle flow is fully-resolved utilizing an immersed boundary method in conjunction with the AMR-WPT method. Both methods are compared for first and second-mode dominated hypersonic transition prediction test cases. A detailed analysis of the simulation results provide insight into the relevant physical mechanisms involved in particle-induced transition. Finally, bi-orthogonal decomposition based on the continuous and discrete eigenmodes of the compressible boundary layer flow is employed to study the receptivity process.