Flow Field Investigations on the SACCON Configuration in Stationary and Pitching Mode by Means of Particle Image Velocimetry

Abstract

Three-dimensional flow field measurements above a stationary and pitching Unmanned Combat Air Vehicle (UCAV) model are performed applying Stereo Particle Image Velocimetry (PIV). The tests took place in the low speed wind tunnel DNW-NWB on a SACCON (Stability And Control CONfiguration) wind tunnel model of NASA. Pitching model motions were applied using a model positioning system of the wind tunnel. This enabled also measurements in several cross planes by moving the model within the test section while keeping the light-sheet and cameras of the Stereo-PIV arrangement stationary. The obtained flow velocity and vorticity distributions are used to analyse the 3D flow topology at static conditions between chord positions of x/c = 0.45 and 0.85 for seven angles of attack between 14° and 19°. The flow dynamic development for a pitching frequency of 1 Hz and two different pitch amplitudes of ±2.5° and ±5° are also discussed at x/c = 0.7 for 8 phase positions, comparing the vortical flow structures with the static results. A hysteresis in the development of the vortices is determined by calculating the circulation strengths of individual vortices.