This paper gives an overview of numerical flow control investigations for high-lift airfoil flows carried out by the authors. Two configurations at stall conditions, a generic two-element setup with single flap and a second configuration with slat and flap of more practical relevance are investigated by simulations based on the Reynolds-averaged Navier-Stokes equations and eddy-viscosity turbulence models. For both cases flow separation can be delayed by periodic vertical suction and blowing through a slot close to the leading edge of the flap. By simulating different excitation modes, frequencies and intensities optimum control parameters could be identified. Comparison of aerodynamic forces computed and flow visualisations to experiments allows a detailed analysis of the dominant structures in the flow field and the effect of flow control on these. The mean aerodynamic lift can be significantly enhanced by the active flow control concepts suggested here. By changing the excitation frequency at a constant intensity an optimum frequency can be identified for the two-component configuration. It corresponds to a sinusoidal lift and detaching vortices of a suitable size. The mean lift coefficient increases by up to 30% compared to the baseline simulation, and separation can be delayed. The effect of Reynolds number turned out not to be crucial for the range 105 < Re < 106 investigated, and the flow control concept could successfully be applied. The behaviour of two completely different configurations showed the same principle influence of the excitation parameters on the resulting flow field. In both cases lift, drag and the mean flap separation could be controlled by parameters that do not differ substantially.
Computational investigation of separation control for high-lift airfoil flows
Numerische Untersuchung der Strömungsabrissregelung für Hochauftriebs-Tragflügelumströmung
2007
17 Seiten, 17 Bilder, 22 Quellen
Aufsatz (Konferenz)
Englisch
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