Study the effects of swirl on a confined coannular jet using LES

Abstract

Large Eddy Simulations (LES) are used to model a turbulent confined coannular combustor and examine the effects of swirl on the flow field and mixing. Three separate simulations with relatively high mesh resolutions and different swirl numbers have been carried out using a finite volume method on a Cartesian non-uniform structured grid. A localised dynamic Smagorinsky model is used to parameterize the subgrid scale turbulence. Results for both instantaneous and time averaged statistics are presented and validated against experimental data. The snapshots of the axial, swirl velocities and velocity vector fields indicate the complex flow patterns developing with increased swirl number and rapid decay of axial momentum. We observe that the radial transport of axial velocity depends on the swirl strength. Precessing vortex cores were identified for all three cases and the mean axial velocity plots indicate that the upstream extremity of the vortex breakdown bubble shifts towards the inlet as the swirl number increases. The radial plots of mean passive scalar and its variance also demonstrate an increase in the rate of mixing with increasing swirl number.

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ORCID for K.K.J. Ranga Dinesh: orcid.org/0000-0001-9176-6834

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