QUANTITATIVE EXPERIMENTAL AND NUMERICAL INVESTIGATION OF A VORTEX RING IMPINGING ON A WALL

A joint experimental and computational methodology is developed and ap plied to investigate a vortex ring impinging normally on a wall. The m ethod uses digital particle image velocimetry to make planar flow meas urements, which are then used to initialize a second-order finite diff erence calculation. The experiment and the simulation are compared at later times and agree extremely well. The ring undergoes two rebounds from the wall and continues to expand. During the approach to the wall , peak vorticity grows by 50% due to vortex stretching. Peak vorticity strengths of the secondary and tertiary vortices formed from the shed ding boundary layer are 40% and 20% of the primary. In addition, a rin g with a Gaussian core is simulated and compared to demonstrate the be nefits of using realistic initial conditions. (C) 1996 American Instit ute of Physics.