Transition induced by an egg-crate roughness on a flat plate in supersonic flow

• DOI: 10.1017/jfm.2022.510
• Publication Date: 2022-09-09T18:06:30Z
• Authors: Amanda Chou; Pedro Paredes; Michael A. Kegerise; Rudolph A. King; Meelan Choudhari; Fei Li
• Keywords: 0103 physical sciences; 01 natural sciences

Hot-wire measurements in a Mach 3.5 quiet tunnel were made the wake of roughness patch on flat plate. These used to determine mode shapes and frequencies dominant instabilities leading boundary-layer transition. The egg-crate pattern is an analytic function described by sinusoidal equation, similar array discrete elements that are positioned spanwise streamwise grid, but containing both protuberances dimples. This intermediate configuration towards understanding underlying physics pseudorandom distributed roughness, ultimately, roughness-induced had wavelength 6.25 mm, with nominal amplitude 272 ${\rm \mu}{\rm m}$ (0.49 times boundary layer thickness at first row protuberances). was near edge plate contained wavelengths direction 7.5 direction. instability centred 74 kHz free stream unit Reynolds number $12.9\times 10^{6}\,{\rm m}^{-1}$ resembled antisymmetric downstream each patch. Computations using linear stability analysis based plane-marching parabolized equations (PSE) showed limited agreement when comparing growth instability. Better observed considering modification waves solution three-dimensional harmonic linearized Navier–Stokes as in-flow PSE. confirms significance disturbance upstream above finite length effect wake.