Instability, turbulence and relaminarization in the attachment-line region of swept and unswept cylindrical bodies are studied by numerical solution of the full Navier-Stokes equations. The flow is simulated over a strip containing the attachment line and treated as homogeneous in the spanwise direction; the disturbances decay exponentially upstream. Transpiration through the wall may be prescribed. The new method, which admits completely general disturbances, agrees with published liner-stability results, which were limited to an apparently restrictive form of disturbance. Fully-developed turbulent solutions with sweep are generated and compare well with experiment. The turbulence is subcritical (except with blowing), resulting in large hysteresis loops. By lowering the sweep Reynolds number, or increasing the suction, the turbulent flow is made to relaminarize. The relaminarzation Reynolds number is much less sensitive to suction than the linear-instability Reynolds number. Extensive attempts to detect the postulated nonlinear instability of the unswept flow failed, suggesting that this flow is linearly and nonlinearly stable.
Direct numerical study of leading-edge contamination
Direkte numerische Untersuchung der Verschmutzung der Fluegelvorderkante
1989
13 Seiten, 9 Bilder, 16 Quellen
Conference paper
English
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