DDES study of the aerodynamic forces and flow physics of a delta wing in static ground effect

During takeoff and landing phases, the performance of an aircraft with delta wing configuration is significantly influenced by the ground effect (GE). In this paper, the static ground effect (SGE) of a 65° sweep delta wing (VFE-2) with sharp leading edge at α=20° is investigated by the Delayed Detached Eddy Simulation (DDES) grounded on Spalart-Allmaras (S-A) turbulence model. With the ride height decreasing, the lift, drag and nose-down pitching moment of the delta wing increase nonlinearly, and the majority of aerodynamic force increments in SGE are from the windward side of the delta wing. With the ride height decreasing, under the windward side, the flow is severely blocked resulting in the augmentation of static pressure, and the increasing span wise flow near the leading edge strengthens the shear layer and the leading edge vortex over the leeward side. The strengthened leading edge vortex induces lower pressure over the leeward side, and moves outside along the span wise direction. With the ride height decreasing, the jet-like flow in the primary vortex core is accelerated before the vortex breakdown, and the wake-like flow in the primary vortex core is decelerated after the vortex breakdown.