Relationship between Preferred Frequency and Diffusion by Jet Density and Exit Velocity Distributions

Abstract

This report aims at investigating the relationship between preferred frequency and diffusion. The disturbance frequency for mixing control based on the preferred frequency occur in a jet flow initial area of a jet column mode is often selected to enhance the diffusion of the jet flow. When the diffusive mixing enhancement such as the gaseous fuel and air is assumed, it is general that a jet flow and a surrounding gas are different. So the jet flow, Air, CO₂, and He were used. And nozzles were three types, converging, orifice and pipe. First, the laser light sheet technique was applied to the visualization of a cross section of vortex ring. The distance until rolling up to the vortex ring goes away from the nozzle as increasing the density ratio. Next, the variation of velocity of a jet flow was measured by the hot wire anemometry and PIV to investigate the preferred frequency to determine the Strouhal number. The Strouhal number does not depend on Reynolds number and keep an almost constant value. These show the relationship between preferred frequency and diffusion by jet density and exit velocity distributions.