Influence of Surface Roughness and Free-stream Turbulence on Crossflow-instability Transition
| Autor: | J. D. Crouch, L.L. Ng, Yury S. Kachanov, A.V. Ivanov, V. I. Borodulin |
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| Rok vydání: | 2015 |
| Předmět: |
Physics
Transition Prediction Variable N-Factor Baseflow Turbulence business.industry K-epsilon turbulence model Turbulence modeling Instability General Medicine K-omega turbulence model Mechanics Surface finish Amplitude Method Roughness Physics::Fluid Dynamics Optics Turbulence kinetic energy Surface roughness business |
| Zdroj: | Procedia IUTAM. 14:295-302 |
| ISSN: | 2210-9838 |
| DOI: | 10.1016/j.piutam.2015.03.052 |
| Popis: | Surface-roughness and free-stream-turbulence effects on crossflow-instability transition are investigated experimentally and theoretically. A model baseflow is established and shown to be well predicted by boundary-layer analysis. Surface roughness is systematically introduced, with a factor-of-50 variation in r.m.s. levels. Free-stream turbulence levels are varied using grids across the test section, providing roughly a factor-of-10 variation in the turbulence intensity. For low turbulence levels, the transition is dominated by stationary crossflow instabilities. As the free-stream turbulence is increased, the traveling crossflow instabilities become increasingly relevant. For higher-turbulence and lower-roughness levels the transition appears to be dominated by the traveling crossflow instabilities. The results are linked to a variable N-factor method, which is shown to provide a good basis for estimating the transition location for low turbulence levels. The variable N-factor method is used to interpret the results and infer causality between roughness, turbulence and transition. |
| Databáze: | OpenAIRE |
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