Two distinct regions in a pulsed-axisymmetric jet

Abstract

This research concerns on the axial measurement of a pulsed-axisymmetric jet to investigate the decay of inverse of mean centerline axial velocity with the use of a single normal hot-wire anemometer. The measurement is performed by controlling mean exit velocity and pulsing frequency. The axial measurement reveals that the pulsation method leads to the appearances of two distinct regions namely the pulsed dominated-and the high turbulence steady jet-regions. However, the existence of the two regions can be controlled by adjusting the mean exit velocity and pulsing frequency. At a high mean exit velocity and low pulsing frequency, the high turbulence steady region is not seen, hence the transition region can not be found. Furthermore, at a high pulsing frequency and a constant mean exit velocity, the pulse dominated region becomes shorter. The present study has provided a comprehensive knowledge in that the trend of the decay rate is very clear under the wide range of pulsation method imposed on the jet. This inclusive understanding becomes a substantial consideration for mixing processes as well as can be used to verify the k-e turbulence model to predict the decay of normalized mean centerline-axial velocity.