Experiments with Unsteady, Free Surface, Three-Dimensional Vortices in a Thermally Stable, Stratified Fluid.

摘要

The unsteady characteristics of a vortex pair formed behind a delta wing airfoil at a negative angle of attack have been studied experimentally in a large towing tank with a stable density stratification. Measurements of the vortex pair's upward migration and visualizations of the vortex circulation were made using the hydrogen bubble technique with a laser sheet illumination in the transverse plane. Axial visualizations of the vortex migration and axial velocities at the vortex core were made using the hydrogen bubble technique with a diffuse light source. The effects of the rising vortices and their circulation on the free surface temperature field was recorded using an imaging infrared radiometer mounted over the free surface. Keywords: Free surface; Flow visualization; Hydrogen bubble; Thermal vortex; Wake detection. (JHD)