Trailing vortex structure with longitudinal core flow

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University of New Brunswick
In this study, Particle Image Velocimetry(PIV) measurements were performed on a vortex have two levels of circulation corresponding to a wing angle of incidence, α = 4° and 8° and two Reynolds number based on wing chord, Rec = 4 x 10^4 and 8 x 10^4. Measurements were made at different locations along the wind tunnel in longitudinal planes, X/C = 2:5, 3:5, 6:5 and 7:5 and cross-sectional planes, X/C = 3 and 7. The effect of longitudinal core flow was evaluated using four levels of jet velocity, Vjet/U∞ = 0, 0:5, 1 and 2, added to the vortex core. Results for the instantaneous, mean and variance of the vorticity field are presented. The mean and variance of velocity on longitudinal plane show the vortex core flow. Vortex wandering is measured and used to correct the mean and variance of the vorticity field. The instantaneous vorticity fields were found to be complex and with elements of co-rotating vortices around the primary vortex and strong circumferential components of vorticity on the core. The vortex radius was smaller for the higher level of circulation cases and tangential velocity was increased by increasing the level of circulation. The jet velocity was observed to have a weak effect on the vortex structure. The variance of longitudinal vorticity was found to be occurred in a ring shape around the vortex core in the cross-sectional plane. The vorticity variance decayed with downstream distance and it was found that the variance of longitudinal vorticity scaled with mean circulation.