Control of Momentum and Heat Transport in a Heated Axisymmetric Jet by Means of Vortex Generators
To control the momentum and heat transport in a slightly heated axisymmetric turbulent jet, small vortex generators (VGs) are inserted into the exit of axisymmetric jet and their effects are experimentally investigated. Experiments are performed at a Reynolds number (Re) of 20,000 (based on the mean velocity of the jet exit and the diameter of the jet exit). We used six small VGs that have a shape of a half-delta wing and generate longitudinal vortices in the downstream direction. These six VGs are fixed around the jet exit at an attack of angle 30° at equal intervals; they are inserted into the initial shear layer of the axisymmetric jet. Heat is regarded as a passive scalar. The instantaneous two component velocities and temperature are simultaneously
measured by a composite probe comprising an X-type hot-wire probe and an I-type cold-wire probe. The results show that both mass entrainment and heat transfer are enhanced near the jet exit by inserting VGs. However, entrainment rate is suppressed further downstream. The profiles of mean velocity, cross-streamwise rms velocity, and cross-streamwise heat flux become similar to those for the case without VGs in the far downstream region.