RANS Calculations and measurements of instabilities in swirl-stabilised jets and flames
Faculty of Computing, Health and Science
School of Engineering
This paper addresses two issues of importance in reacting and non-reacting swirling flows: the nature of the instability which appears to dominate over arange of swirl numbers and the capabilities of Reynolds Averaged Navier-Stokes (RANS) approaches to compute such flow complexities. Unsteady, three dimensional RANS calculations of swirling jets and flames are performed here using the k-ε model of turbulence and the very simple, eddy breakup combustion model. Measurements of flow instabilities, such as precession frequencies, occurrence of vortex breakdown and instantaneous images of jets are also presented. This paper demonstrates that the RANS approach, despite its relative simplicity, is capable of reproducing the flow-field and instabilities of the swirling jets adequately at low swirl numbers. High swirl numbers are much more complex and therefore, are less adequately predicted. The model is unable to predict the transient behavior of flames.