LARGE EDDY SIMULATION OF ISOTHERMAL TURBULENT SWIRLING JETS

Abstract

This article investigates the application of the large eddy simulation (LES) technique to turbulent isothermal swirling flows. The aim was to improve our understanding of the flow physics and turbulence structure of unconfined swirling flows and examine the capability of LES to predict the formation of the vortex breakdown (VB) and recirculation zones. In this study, the filtered Navier-Stokes equations are closed using the Smagorinsky eddy viscosity model with the localized dynamic procedure of Piomelli and Liu (1995). The Sydney University swirl burner experiments are simulated as test cases. Three different test cases have been investigated covering a range of swirl numbers and stream wise annular velocities. The cases considered have swirl numbers ranging from 0 to 1.59 and Reynolds numbers from 32400 to 59000. The LES calculations confirm that the combination of lower swirl number and higher axial velocity of the primary annulus leads to the establishment of the downstream vortex breakdown region. For the cases considered, the LES calculations were successful in predicting observed recirculation zones, vortex breakdown and showed good agreement with experimentally measured mean velocities, their rms fluctuations and Reynolds shear stresses.