EFFECT OF NOZZLE CONFIGURATION ON TRANSPORT IN THE STAGNATION ZONE OF AXISYMMETRICAL, IMPINGING FREE-SURFACE LIQUID JETS .1. TURBULENT-FLOW STRUCTURE

This study characterized the mean and fluctuating parts of the radial component of the local velocity in the stagnation region of an impinging, free-surface liquid jet striking a smooth flat plate. Four different nozzle exit conditions were studied, including fully developed pipe flow, a contoured nozzle, and turbulence-damped and -undamped sharp-edged orifices. Liquid jet Reynolds numbers in the range 30,000 to 55,000 were investigated. Velocities were measured using laser-Doppler velocimetry. Mean velocities were found to vary nearly linearly with radial location, with the slope of the line being a function of distance from the impingement plate. Dimensionless mean velocity gradients, of relevance to the heat transfer, were found to be a strong function of nozzle type, but roughly independent of jet Reynolds number for a given nozzle type. Turbulence levels were also found to be strongly influenced by the nozzle exit condition. Local heat transfer data corresponding to the flow structure measurements presented here are reported in Part 2 of this study.