An Experimental Investigation of Leading Edge Vortical Flow about a Delta Wing during Wing Rock
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The primary objective of this research was to further investigate the dynamic motion of an 80 deg delta wing during wing rock in both a water and wind tunnel. Both vortical flow data and wing motion data were recorded using a video-based motion analysis system. This system provided adequate means to nonintrusively measure dynamic data. The data revealed hysteresis differences between the wind tunnel and water tunnel tests. Hysteresis in the rolling moment coefficient versus bank or roll angle, during water tunnel testing, traveled in the direction opposite to the wind tunnel results. Visualization of the water tunnel vortical flowfields provided quantified right and left vortex locations at specific roll angles during wing rock. The contribution to the rolling moment based on these vortex positions was analyzed. Results show a decrease in rolling moment before reaching the maximum roll amplitude and an increase in rolling moment after passing through the maximum roll angle. Added mass experiments were also conducted in the wind tunnel. The wind tunnel rolling moment was 15 times larger than water tunnel results, due to the difference in densities of the mediums. Although dynamic similitude was not achieved between the two fluids, a foundation for further investigation has been laid.