1193 Measurement of axial turbulent scalar flux of high Sc/low Re round jet using line scan camera

Abstract

In this study, simultaneous measurement of axial velocity and concentration is carried out along the centerline axis of turbulent round jet in the self similar region using line scan camera. Line scan camera enables us to measure the light intensity at multiple positions as many as 2048 simultaneously at high acquisition rate as high as 100k Hz. Reynolds number based on nozzle diameter and nozzle exit velocity is relatively low of 3200. Rhodamine B (fluorescent dye) solution is issued from the nozzle into a test water tank. Schmidt number is 2380. Jet axis is illuminated by green line laser and concentration of Rhodamine B solution is measured by LIF method. Instantaneous concentration profile recorded by line scan camera shifts downstream with time proceeding. Correlation image technique is applied to estimate local and instantaneous axial velocity. Spatial resolution of concentration measurement is smaller than Kolmogorov scale but greater than Batchelor scale. Scalar dissipation cannot be measured directly but can be estimated from turbulent scalar flux since velocity and concentration are measured simultaneously. Batchelor spectrum, which is proportional to the inverse of wave number, is observed.