Mean flow and turbulence measurements in the near field of a fighter aircraft wing-tip vortex at high Reynolds number and transonic flow conditions

Institute for Aerospace Research National Research Council Canada Ottawa, Ontario, Canada K1A 0R6

Abstract

Mean and turbulent flow characteristics of the wing-tip vortex generated by a 6% scale model of the F/A-18 fighter aircraft equipped with AIM-9 sidewinders were investigated experimentally. This particular configuration was studied as part of the NRC/IAR stores clearance and certification program. However, the present study focuses on the near field structure of the tip vortex, as the existing literature contains relatively little information on tip vortices generated at such high Reynolds numbers (4.4´ 10⁶, based on wing chord), and even less on the tip vortices of fighter aircraft. The experiments were conducted in the transonic test section of the NRC/IAR 1.5m x 1.5m trisonic blowdown wind tunnel. The present paper documents results obtained in a single cross-flow plane located immediately downstream of the wing trailing edge, for two angles of attack, 4.5° and 13° , and at a single freestream Mach number of 0.75. Mean velocities and flow angularities were measured using a five-hole directional velocity probe as well as an x-array constant temperature hot-wire probe. The latter also provided estimates of the turbulence intensities, Reynolds stresses and turbulent kinetic energy in the measurement plane. The results shed some light on the fairly complex interaction, particularly at the higher angle of attack, of the wing-tip vortex and the wake of the AIM-9 tip missile.