Influence of Surface Roughness and Free-stream Turbulence on Crossflow-instability Transition☆

摘要: Abstract Surface-roughness and free-stream-turbulence effects on crossflow-instability transition are investigated experimentally theoretically. A model baseflow is established shown to be well predicted by boundary-layer analysis. Surface roughness systematically introduced, with a factor-of-50 variation in r.m.s. levels. Free-stream turbulence levels varied using grids across the test section, providing roughly factor-of-10 intensity. For low levels, dominated stationary crossflow instabilities. As free-stream increased, traveling instabilities become increasingly relevant. higher-turbulence lower-roughness appears The results linked variable N-factor method, which provide good basis for estimating location method used interpret infer causality between roughness, transition.