Forebody Slot Blowing on Vortex Breakdown and Load Over a Delta Wing

Abstract

shows that a forebody slot blowing technique significantly delays vortex breakdown over a delta wing. Blowing only on one side while delaying vortex breakdown has an opposite effect on the nonblowing side. Although the authors provided a plausible explanation for the observed behavior, no concrete evidence was given. In this paper, we address this issue and further evaluate the effects of symmetric and differential blowing on the aerodynamic loads. Flow visualization and force measurement were carried out in a water tunnel at a Reynolds number of 8:5 10 4 . Our study shows that the differing effect of differential blowing can be traced to a combination of forebody slot blowing itself and the interaction of the vortices from both sides resulting in a side-slip-like effect. Moreover, symmetrical forebody slot blowing, apart from producing a significant delay in the formation of vortex breakdown, increases the lift by more than 5%. Differential blowing can be used to manipulate the vortex breakdown position and change the roll moment of the wing, which suggests that the method can be a potential means for roll control. Nomenclature= blowing momentum coefficient for port side slot C S = blowing momentum coefficient for starboard side slot c = root chord Q = volume flow rate of blowing q = dynamic pressure of freestream Re = Reynolds number, Uc=v S = area of delta wing U = freestream velocity V j = average slot exit velocity X b = vortex breakdown position from the apex of the wing X bmean = mean vortex breakdown position X bmean P = mean port side vortex breakdown position X bmean S = mean starboard side vortex breakdown position = kinematic viscosity of water = density of blowing fluid