Scattering of Tollmien-Schlichting waves by localized roughness in transonic boundary layers |
| |
| Authors: | Ming DONG |
| |
| Affiliation: | 1. Department of Mechanics, Tianjin University, Tianjin 300072, China;2. Laboratory for High-Speed Aerodynamics, Tianjin University, Tianjin 300072, China |
| |
| Abstract: | The laminar-turbulent transition in boundary-layer flows is often affected by wall imperfections, because the latter may interact with either the freestream perturbations or the oncoming boundary-layer instability modes, leading to a modification of the accumulation of the normal modes. The present paper particularly focuses on the latter mechanism in a transonic boundary layer, namely, the effect of a two-dimensional (2D) roughness element on the oncoming Tollmien-Schlichting (T-S) modes when they propagate through the region of the rapid mean-flow distortion induced by the roughness. The wave scattering is analyzed by adapting the local scattering theory developed for subsonic boundary layers (WU, X. S. and DONG, M. A local scattering theory for the effects of isolated roughness on boundary-layer instability and transition:transmission coefficient as an eigenvalue. Journal of Fluid Mechanics, 794, 68-108 (2006)) to the transonic regime, and a transmission coefficient is introduced to characterize the effect of the roughness. In the sub-transonic regime, in which the Mach number is close to, but less than, 1, the scattering system reduces to an eigenvalue problem with the transmission coefficient being the eigenvalue; while in the super-transonic regime, in which the Mach number is slightly greater than 1, the scattering system becomes a high-dimensional group of linear equations with the transmission coefficient being solved afterward. In the largeReynolds-number asymptotic theory, the Kármán-Guderley parameter is introduced to quantify the effect of the Mach number. A systematical parametric study is carried out, and the dependence of the transmission coefficient on the roughness shape, the frequency of the oncoming mode, and the Kármán-Guderley parameter is provided. |
| |
| Keywords: | boundary layer scattering instability Tollmien-Schlichting (T-S) wave triple deck Chinese Library |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《应用数学和力学(英文版)》浏览原始摘要信息 |
|
点击此处可从《应用数学和力学(英文版)》下载全文 |
|
