Computational and Experimental Investigation of the Aerodynamics of a W-shaped leading edge reversed delta plan-form wing
A feasibility analysis for an unconventional W-shaped leading edge, reversed delta plan-form wing has been carried out. The wing is believed to aid the Vertical/Short Take-off and Landing (V/STOL) capabilities of small aircraft. The main focus of the research was to carry out computational investigations of the flow phenomena associated with this unique shaped wing at cruise, take-off, and landing configurations. An interactive numerical and experimental method was used to baseline the important flow-field structures associated with this wing, and to identify the necessary areas for further comprehensive full-scale numerical investigations carried out herein. Numerical simulations solved the explicit quasi-steady compressible Navier-Stokes equations for the cruise conditions (run at a Reynolds Number of 3x107), while segregated quasi-steady incompressible Navier-Stokes equations were solved for the ground-effect analyses and low-speed wind tunnel simulations on a 5% scale of the wing (run at Reynolds Number of 3x105 and 3.6x105).Numerically, the ground was accounted for with the image method, and the static ground board method. The fuselage was not modelled in the numerical or experimental investigations. Hence, it needs to be noted that the additional lift-dependant drag caused by the modification of the span loading due to fuselage has not been accounted for. Also, the there are limitations on the ground height limited by the inclusion of the fuselage. In general, the wing was found to have a highly three-dimensional flow field. Both low-speed and high-speed free-flight results revealed that the wing exhibits soft stall and a good lift-to-drag ratio, as well as statically stable pitching moment response up to stall conditions. Maximum lift was reached at 14°< α < 16°, giving a lift-to-drag ratio of 18. On-surface streamline observations showed that the effect of the forward sweep assists in terminating the propagation of the flow separation along the entire part of the wing. High-speed numerical investigations showed regions of local supersonic flow, but with no detrimental effects on the performance of the wing. Near-wake results by both means of study revealed inboard vortex phenomena at higher angle of attack. The ground-effect results showed a great increase of the lift coefficient and lift-to-drag ratio for the W-wing in ground effect. Values of L/D=30 were achieved for h/b = 0.09, a 90 % increase as compared to the free-flight case. Regions of very low velocity and high pressure underneath the wing were resolved, suggesting a very strong “air cushion” effect being induced by the wing. Modification of the wing design suggested that in absence of the forward-sweep, the un-swept wing struggles to maintain attached flow, or indeed prevent further separation on the rest of the wing.
TA Engineering (General). Civil engineering (General), TL Motor vehicles. Aeronautics. Astronautics
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