Tail Buffet of F/A-18 at High Incidence with Sideslip and Roll (Part 2)

Abstract

In Part 1 the variations of the mean and rms normal force, bending and torsional moment coefficients on the vertical fin of an F/A-18 aircraft for different orientations and Mach numbers were examined by integrating the measured pressure differences across the fin's surfaces. We examine statistically the fin loading with particular attention paid to the relationships between the normal force coefficient and the local surface-pressure fluctuations. Space-time pressure correlation studies were conducted to estimate the average convection velocities and paths of the coherent turbulent structures over the two surfaces of the fin. Power spectra for the force and moments were also computed. Within ranges of small to moderate sideslip and roll angles, all spectra contained distinct peaks at the same nondimensional frequency for a fixed Mach number and angle of attack. Only results at an incidence of 30 deg are reported here, as representative of results at three angles of attack (25, 30, and 32.5 deg)