Impact of Air Injection on the Hydrodynamic Performance of a Reverse Delta Wing Operating in Submerged to Airborne Conditions

The wings of ground effect vehicles operating over water experience transition from submerged operation during takeoff to fully airborne during flight. This experimental study investigates the impact of an air injection jet on the hydrodynamic performance of a reverse delta wing during this transition regime. The wing model was tested across blowing coefficients (Cμ) from 0 to 2.6– corresponding to Reynolds numbers varying from 0 to 264,000, and Nozzle Pressure Ratios, NPR, of 1 to 1.4 (representing mass flow rates between 0 and 0.1 kg/s). Tests at those conditions were conducted at angles of attack, α, ranging from −2° to 8°, and wing positions from 16% chord depth below the water surface to 8% chord height above the surface. Air injection produced complex effects on wing performance. at low to moderate NPR, both lift and drag initially increased, while at moderate to high NPR, lift and drag decreased across nearly all heights. Notably, drag, under some conditions, became negative (producing thrust). Flow visualization showed dramatic changes in the air injection cavity shape and depth with varying NPR, Re, and height.