Global receptivity analysis: physically realizable input–output analysis. (10th February 2023)

• Record Type: Journal Article
• Authors: Kamal, Omar; Lakebrink, Matthew T.; Colonius, Tim
• Is Part Of: Journal of fluid mechanics. Volume 956(2023)
• Publication Date: 2023-02-10
• Subjects: high-speed flow -- boundary layer receptivity -- boundary layer stability; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2023.48
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : In the context of transition analysis, linear input–output analysis determines the worst-case disturbances to a laminar base flow based on a generic right-hand-side volumetric/boundary forcing term. The worst-case forcing is not physically realizable, and, to our knowledge, a generic framework for posing physically realizable worst-case disturbance problems is lacking. In natural receptivity analysis, disturbances are forced by matching (typically local) solutions within the boundary layer to outer solutions consisting of free-stream vortical, entropic and acoustic disturbances. We pose a scattering formalism to restrict the input forcing to a set of realizable disturbances associated with plane-wave solutions of the outer problem. The formulation is validated by comparing with direct numerical simulations of a Mach 4.5 flat-plate boundary layer. We show that the method provides insight into transition mechanisms by identifying those linear combinations of plane-wave disturbances that maximize energy amplification over a range of frequencies. We also discuss how the framework can be extended to accommodate scattering from shocks and in shock layers for supersonic flow.