Impact of Air Injection on the Aerodynamic Performance of a Reverse Delta Wing Operating in Ground Effect*

Ground effect vehicles experience increased lift when flying within a chord length of a solid boundary. This experimental study investigates the impact of air injection on the aerodynamic performance of a reverse delta wing operating in ground effect. The model was tested at Reynolds numbers, Re, varying from 0 to 672,000, at angles of attack, α, ranging from 0 to 20°, and at ground-to-wing spacings of 5, 30, and 100% of the wing chord. The mass flow of the injected air ranged from 0 to 0.187 kg/s. The largest impact of injection occurred at a 5% chord height, 0.187 kg/s air injection rate, and at an angle of attack of 20°. Here lift increased by approximately 8 times compared to the no-injection condition. For this same condition, the measured drag force decreased by a factor of 1/3. Flow visualization of several test points showed air injection reduced the extent of the region of separated flow that occurred at higher angles of attack on the suction side of the wing. Air injection was not universally beneficial, for instance, at 5% chord height and α = 0°, the lift initially decreased with increased air injection, before later increasing as the air injection rate continued to increase. This "suck down" effect is documented in jet literature. The impact of increasing air injection and α were generally symbiotic in increasing lift.