The effect of hole geometry on lift-off behavior of coolant jets

Water tunnel experiments have been conducted to understand the effect that hole exit geometry has on the lift-off characteristics of a jet in a crossflow stream. The following basic hole shapes were investigated, all having approximately the same cross-sectional area: round, elliptical, square, and rectangular. Laser Induced Fluorescence (LIF) was used to visualize the jet structure in the region near the hole exit. Both jet trajectory and jet cross-section views provide insight into the basic characteristics of the jet, which are strongly dependent on the formation of kidney-shaped vortices. Particle Image Velocimetry (PIV) was used to obtain the velocity field in the region immediately downstream of the jet. Based on the LIF and PIV results, hole geometry alone was found to influence the basic character of the jet, therefore, effecting the lift-off behavior.