The evolution of wandering motion and statistic characteristics of wingtip vortex in grid turbulence

Freestream turbulence significantly affects the unstable wandering motion and the evolution of the wingtip vortex. In the present study, time resolved-stereo particle image velocimetry (TR-SPIV) measurements were carried out under different freestream conditions at a chord-length-based Reynolds number of Re_c = 1.1 × 10⁴. The results show that grid turbulence significantly enhances the wandering motion of the wingtip vortex. The wandering amplitude increases linearly along the streamwise direction and scales well with freestream velocity fluctuations. The ‘smearing out’ effect of vortex wandering on the statistic characteristics is dramatic and can be corrected by the ensemble average method. Moreover, it is found that the core radius follows the same growth law under different flow configurations involved in the measured parameter space, indicating that the evolution of the wingtip vortex along the streamwise direction is dominated by viscous diffusion.