Measurements of the velocity field of a wing-tip vortex, wandering in grid turbulence

Abstract

Velocity measurements were performed in a wing-tip vortex wandering in free-stream turbulence using two four-wire hot-wire probes. Vortex wandering was well represented by a bi-normal probability density with increasing free-stream turbulence resulting in increased amplitude of wandering. The most dominant wavelength of wandering was found to remain unaffected by free-stream conditions. Two-point velocity measurements were used to reconstruct the vortex velocity profile in a frame of reference wandering with the vortex. Increasing turbulence intensity was found to increase the rate of decay of the vortex peak circumferential velocity while the radial location of this peak velocity remained unchanged. These results are consistent with several possible vortex decay mechanisms, including the stripping of vorticity by azimuthally aligned vortical structures, transfer of angular momentum from the vortex to these structures during their formation and the deformation and breakup of the vortex by strong free-stream eddies.