Numerical study of aerodynamics of a wing-in-ground-effect craft

The flow around a wing-in-ground-effect craft flying at α 3 deg and α 9 deg over flat and wavy ground is simulated and investigated by using ANSYS FLUENT, employing the compressible Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model. The sliding mesh technology is used to simulate the relative motion between the wing-in-ground-effect craft and wavy ground. The effects of the wavy ground, flight height, and angle of attack on the aerodynamic characteristics and flowfield are analyzed in detail. The aerodynamic forces are found to be periodic when the wing-in-ground-effect craft flies over wavy ground. The aerodynamic forces over both flat and wavy ground vary with flight height in the same pattern. As the flight height reduces, the lift, drag, and nose-down pitching moment all increase at both angles of attack (α = 3 deg and α = 9 deg); however, the liftto-drag ratio increases for all flight heights at α = 3 deg, while it first increases and then decreases at α = 9 deg. Reduction in the flight height at α = 9 deg eventually causes the attached flow to evolve into separated flow on the upper surface of the wing. Therefore, at higher angle of attack of α = 9 deg, the lower the flight height is, the larger is the flow separation region; thus, the lift-to-drag ratio increases to the maximum at a certain flight height and then begins to decrease as the flight height decreases.