Experimental studies of vortex flaps and vortex plates

Abstract

Low-speed wind-tunnel tests have been made on a number of vortex flap and vortex plate configurations at the Cranfield Institute of Technology. The objectives of the experiment are to assess the benefits of these devices on the lift/drag ratio improvement of delta wings. The force and surface pressure measurements were made on a 1.15-m span, 60-deg delta wing model. Results indicate that the vortex flap deflection angle, which causes the flow to attach on the flap surface without any large separation, shows a much higher lift/drag ratio than the flap deflection angle which forms a leading-edge separation vortex over the flap surface. The performance of a vortex plate protruding from the leading edge of the datum delta wing is comparable to that of the vortex flap. However, when the vortex plate is used with the vortex flap deflected, it showed no benefit in these tests. Nomenclatureusing Cr and measured about xlCr = 0.4 Cp = pressure coefficient Cr -wing centerline chord, m g ~ vortex plate leading-edge position measured from leading edge of the wing in the chordwise direction, m LID = lift/drag ratio Re Cr -Reynolds number based on wing centerline chord U x = freestream velocity, m/s x -chordwise coordinate measured from the apex of the delta wing, m y = spanwise coordinate orthogonal to x, measured from the wing centerline, m a -wing incidence, deg a g = geometrical wing incidence (i.e., without tunnel corrections), deg 8 f -vortex flap deflection angle measured normal to the hinge line, deg

Effects of Anhedral and Dihedral on a 75-deg Sweep Delta Wing

“…This effect does however result in improved high a performanceas the maximum lift coef cient peak occurs at higher a . 6 Performance of a wing with vortex aps improves overall, as the reduction in drag outweighs the loss of lift. LEVF performance is limited by the inboard migration and expansion of the leading-edge vortices with incidence.…”

Low-Reynolds-Number Airfoil Investigation of Lower-Surface Leading-Edge Flaps

“…Lower-surface leading-edge plates have been evaluated by Traub [13], Rinoie and Stollery [14], and Rao and Johnson [15] as a means of enhancing the performance of delta wings and delta wings with vortex flaps by augmenting and concentrating leading-edge vortex suction. The plate was constituted of a thin metal sheet attached below the leading edge and projecting out so as to be coincident with the leading edge when viewed from above.…”

Flow field measurements of leading-edge separation vortex formed on a delta wing with vortex flaps

“…Many tests have been made which confirm the benefit of the LEVF (Campbell and Osborn, 1986). The author has made experimental studies using delta wing models that have sweepback angles L of 50°, 60°and 70°, fitted with tapered vortex flaps (Rinoie and Stollery, 1994;Rinoie et al, 1997;Rinoie, 1997). Purposes of these studies were to confirm the benefit of the LEVF and to know how the difference of the sweepback angle affects the aerodynamic characteristics of the wing with the LEVF.…”

“…Throughout these studies, it was revealed that the highest lift/drag ratio for the 60°delta wing is achieved using a modest LEVF deflection angle that causes the flow to attach on the flap surface without any large separation (Rinoie and Stollery, 1994). On the contrary, the maximum lift/drag ratio for the 70°delta wing is attained, when a separated region is formed on the vortex flap and when the spanwise length of this separated region almost coincides with the vortex flap width .…”

“…These results suggest that the formation and the behavior of the leading-edge separation vortex over the LEVF surface should be investigated more in detail, in order to get the maximum understandings of the performance of the LEVF. In this paper, both the behaviors of the leading-edge separation vortex formed on the LEVF and the effect of the LEVF over the delta wing performance \:~11l111I J' (Rinoie and Stollery, 1994).…”