Experimental study of aerodynamics of an airfoil with airbrake

Abstract

A low-speed wind tunnel study was performed on a generic sailplane laminar airfoil section equipped with airbrakes of different geometric configurations. The fundamental effects of an airbrake are evident - loss of lift and increase of drag. The motivation was to provide and extend data valid for aerodynamic design of current sailplanes and light aircraft where the airbrakes are used as a standard device. The study was focused on the influence of the basic geometric parameters of the airbrake, on its global aerodynamic performance, on the pressure distribution of the airfoil surfaces and on the separation of flow. Two essentially distinct geometric configurations of the airbrake were studied - the airbrake on the airfoil upper surface only and the airbrakes on both the upper and lower surfaces. Also studied were the influence of the chordwise position of the airbrake, of the airbrake height and of a gap between the airbrake plate and the airfoil. Forces and moment measurements, surface pressure distribution measurements, PIV (Particle Image Velocimetry) and surface visualizations using minitufts were performed. The aerodynamic influence of a box in the wing housing the airbrake was studied using CFD (Computational Fluid Dynamics) software.