Aerodynamics and Flow Physics of a Delta Wing Under Static Ground Effect and Sideslip Coupling

Abstract Fighter aircraft should be capable of safe takeoff and landing under strong crosswind conditions; thus, studies on the aerodynamics of delta wings under the coupling of static ground effect (SGE) and sideslip are of considerable significance. In this paper, the aerodynamic characteristics and underlying flow physics of the standard delta wing model VFE-2 under SGE and sideslip coupling are systematically investigated using the computational fluid dynamics method and the full-process vorticity transport analysis method. At high flight heights (H/CR > 0.5), the sideslip is the primary contributor to the aerodynamic forces while the effect of SGE is negligible. Only at low flight heights (H/CR < 0.5) does the SGE-sideslip coupling become increasingly prominent. This coupling governs the aerodynamic forces and flow patterns on the lower wing surface: the SGE primarily increases pressure across the entire span via the ground blocking effect; while the sideslip primarily affects the local flow around the reattachment lines, moving the reattachment lines toward the windward edge, increasing the pressure along the reattachment line on the windward side and decreasing it on the leeward side. In contrast, the sideslip remains the dominant factor to the asymmetric evolution of leading-edge vortex (LEVs) on the upper wing surface as well as the corresponding aerodynamic forces. As the sideslip angle increases, the windward LEV breaks down prematurely before bending toward the freestream, while the leeward LEV remains concentrated and gradually straightens to align with the freestream.