Experimental Simulation of Transonic Vortex-Airfoil Interactions

摘要

Results from an experimental investigation of helicopter rotor blade-vortex interaction (BVI) phenomena at transonic Mach numbers and at Reynolds numbers representative of actual helicopter flight operations are presented. The study examined both perpendicular (vortex core perpendicular to the blade leading edge) and parallel (vortex core parallel to blade leading edge) interaction geometries. The significant results are: 1. Perpendicular Interaction: The effect of the vortex causes a large reduction in upper surface pressure distribution (lift increase). This lift increase correlates with strength of the vortex and closeness of the vortex encounter. The interaction is most pronounced near the leading edge of the airfoil. A large spanwise deflection of the vortex is observed as it passes over the airfoil. 2. Parallel Interaction: A similar reduction in upper surface pressure distribution is also observed during the transient passage of the parallel vortex over the airfoil. Like the perpendicular interaction, this effect is also most pronounced near the leading edge, which is in contrast to the general results of numerous CFD simulations. For certain combinations of vortex strength and encounter distance, a class-C shock motion (forward propagation of the airfoil shock wave) was observed. Keywords: Blade vortex interaction; Transonic aerodynamics. (jhd)