Showing papers by "Othon K. Rediniotis published in 2006"

Preliminary Parametric Study of Gurney Flap Dependencies

Abstract: Introduction T HE Gurney flap1,2 is typically a small plate, which is attached at or near the trailing edge of an airfoil on the pressure side The flap has been shown to be a highly effective small-scale (typically 05–15% of the chord) modification that can achieve significant lift and pitching-moment generation1,2 The Gurney functions by essentially increasing the downward deflection of the trailingedge flow, facilitated through the formation of a series of counterrotating vortices similar to that of a von Karman vortex street A subsequent effect is an apparent violation of the trailing-edge Kutta condition; experimental data show that finite loading is carried to the trailing edge The Gurney flap increases the effective chord and camber of the airfoil, so by augmenting circulation Liebeck3 suggested a flow pattern where a “virtual” cusped trailing edge is formed downstream of the Gurney from the shear layers merging downstream of the flap The final pressure recovery would then occur off-surface, which is analogous to violation of the Kutta condition Experimental and computational studies exploring the effect of Gurney flaps have been undertaken covering effects of flap height,4 angle,5 effects on multi-element airfoils,2 etc In this Note, the database is increased through evaluation of the effects of flap porosity, inclination, and spacing from the surface It would also be useful for experimental design and conceptual understanding to have correlations that relate Gurney-flap geometric parameters to performance Consequently, such correlations are developed

Preliminary Flight Tests of a Hinge-Less Roll Control Effecter

Abstract: Introduction T HERE has been a growing research effort to achieve effective hinge-less flight control, spurred on by advances in fluidic control. For purposes of stealth, reduced vehicle weight, increased robustness and damage tolerance as well as compactness, hinge-less methodology is extremely attractive. Hinge-less control can be implemented through either continuous or oscillatory flow manipulation. Continuous manipulation can be achieved using blowing. Past research efforts have shown jet flaps1,2 and circulation control3,4 to be effective at augmenting lift and varying pitching moment. A recent study has shown that a highly deflected (normal to the surface) jet flap can match the performance of a Gurney flap using moderate jet momentum coefficients.5 However, continuous blowing invariably requires drawing air off the engine’s compressor or using shaft power to drive a compressor. Ducting is also required to route the air through its ejection path. Consequently, weight and thrust penalties can be incurred. It would be advantageous to the designer to have the flexibility to employ a modular air-injection system that can be placed locally where control is required. The system can be configured to function as a jet flap or used for augmenting existing control effecters (forming a blown flap). Such a system would have the advantage of not requiring pneumatic lines and can be employed in flight vehicles where a pneumatic source is not present (e.g., unmanned aerial vehicles). In this Note we detail the design and implementation of a self-contained modular blower system. Blower design details are elucidated, as are verification of the blower’s effectiveness as a roll control device through flight testing.