Aerodynamic Characteristics Of High-speed Wing-in-ground Craft

In this paper,the finite volume method is used to solve the compressible Navier-Stokes equation,and the aerodynamic characteristics of high-speed wing in gound effect under different operating conditions are numerically studied.The main contents and results of the study are as follows:(1)Different geometrical parameters and flight heights of the airfoil under high-speed ground effect conditions are numerical simulated,analyzed the influence of geometric shape and flight height on airfoil aerodynamic characteristics,optimized the airfoil under ground effect.The results show that under the conditions of Ma = 0.5 and 6 deg angle of attack,the larger camber and recessed trailing edge airfoil have a larger lift-to-drag ratio,which is suitable for the design of high-speed wing-in-ground vehicles.As the flying height decreases,the increase in lift force caused by the increase in pressure on the lower surface is greater than the suction loss on the upper surface,and the lift coefficient and lift-to-drag ratio increase significantly.(2)The aerodynamic characteristics of the 3D wings under high-speed ground effect are studied.The wing with small sweep angle and large root tip ratio has greater lift and drag in high-speed ground effect.As the flying height decreases,a high-pressure air cushion is formed on the lower surface,and the wingtip vortex moves outwards,increasing the effective aspect ratio and the lift-to-drag ratio of the wing.The end plate blocks the flow of the wing tip,maintains the pressure difference between the upper and lower surfaces,weakens the strength of the wing tip vortex,and reduces the induced drag of the wing.(3)The separation flow of rectangular and waving wings under high-speed ground effect for large angle of attack are numerical simulated,and the aerodynamic characteristics and flow control methods of ground effect wings under stall conditions are studied.The results show that under the condition of high angle of attack at high speed gound effect,the upper surface of the rectangular wing is covered by the recirculation redions,and a pair of vortex structures rotating in opposite directions are formed,which are periodically shed.The flow on the upper surface of the waving wing remains attached at the peak position,and separates at the valley position and forms the flow direction and spanwise vortex structures respectively.With two wavelengths as the period,the flow direction vortex and the spanwise vortex are distributed side by side in the flow field.The spanwise wave wing can effectively reduce the upper airfoil recirculation redions,suppress the lift coefficient fluctuation,and at the same time increase the lift and reduce the drag.