TY - JOUR T1 - On the Generation of Instability Tollmien-Schlichting Waves by Free-Stream Turbulence AU - Shen , Luyu AU - Lu , Changgen JO - Advances in Applied Mathematics and Mechanics VL - 2 SP - 429 EP - 438 PY - 2018 DA - 2018/05 SN - 9 DO - http://doi.org/10.4208/aamm.2015.m998 UR - https://global-sci.org/intro/article_detail/aamm/12157.html KW - Free-stream turbulence, Tollmien-Schlichting wave, boundary layer. AB -

The beginning of the transition from the laminar to a turbulent flow is usually the generation of instability Tollmien-Schlichting (T-S) waves in the boundary layer. Previously, most numerical and experimental researches focused on generating instability T-S waves through the external disturbances such as acoustic waves and vortical disturbances interacting with wall roughness or at the leading-edge of flat-plate, whereas only a few paid attention to the excitation of the T-S waves directly by free-stream turbulence (FST). In this study, the generating mechanism of the temporal mode T-S waves under free-stream turbulence is investigated by using direct numerical simulation (DNS) and fast Fourier transform. Wave packets superposed by a group of stability, neutral and instability T-S waves are discovered in the boundary layer. In addition, the relation between the amplitude of the imposed free-stream turbulence and the amplitude of the excited T-S wave is also obtained.