Numerical simulation of flow and thermal characteristics of harmonic pulsed laminar impinging streams

Abstract

Pulsed jets in various configurations have shown potential for improving transport phenomena. In this study, a system of confined laminar two-dimensional pulsed impinging streams of air is simulated numerically by solving the governing conservation equations using the control volume method. The key parameters examined in this study are as follows: frequency and amplitude of pulsation, mean jet Reynolds number and phase difference between the nozzle exit velocity profiles. The effects of these parameters are computed and discussed comprehensively. Temperature is used as a passive tracer to quantify the degree of mixing in the system. Results show that flow pulsation has significant effects on the flow field, vortex formation and secondary structures, which are generated. These vortex structures influence the thermal shear layer and improve the mixing behavior. A better mixing index is observed as a result of the formation of larger vortices due to increased amplitude of the pulsation velocity amplitude. In the range of parameters tested, the frequency of the pulsation is found to have negligible effect on the mixing behavior of the system. Also, it is observed that by introducing a phase difference between the two jet velocity profiles, the stagnation point oscillates between the two jets and, in general, the system with phase differences shows better mixing behavior. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.