Velocity and temperature measurements in an axisymmetric turbulent jet with cloud-like off-source heating

Abstract

A laboratory analogue consisting of a volumetrically heated turbulent axisymmetric jet was created to study the effect of latent heat release on entrainment in cumulus clouds. The jet fluid was selectively heated in the experiment to simulate condensation heat release in clouds. Whole-field velocity and temperature measurements were conducted in the axial plane of the jet in the heat injection zone (HIZ). Results are presented for varying Reynolds number and non-dimensional heat injection rate. We find that the entire HIZ can be divided into three sub-zones with sharp differences in flow properties based primarily on the nature of the cross-stream velocity profile. The cross-stream velocity profile shows a gradual disappearance of the region of outflow near the jet axis which can be attributed to the acceleration of the jet due to added buoyancy. The streamwise velocity profile also changes from a Gaussian to a flat-top Gaussian. The appearance of a twin-peak Gaussian profile for the temperature has been identified as the reason for this change in the streamwise velocity profile. The temperature profile changes to a flat-top Gaussian towards the end of the HIZ. These differences in the flow profiles are linked to the different decay rates of the axial velocity of heated and unheated jets. An empirical model incorporating the varying decay rates is also proposed.