Very-Large-Eddy Simulation of Nonreactive Turbulent Flow for Annular Trapped Vortex Combustor

A hybrid Reynolds-averaged Navier-Stokes (RANS) large eddy simulation (LES) method is applied in this work. It called very-large-eddy simulation (VLES) turbulence closure model. The aim of this present study is firstly to validate the accuracy of this method for a specific engineering application (a trapped vortex combustor) and secondly to describe its flow characteristics. The trapped vortex combustor is a new concept that utilizes a large recirculation vortex to stabilize the flame. An accurate prediction of the turbulent flow is meaningful for the trapped vortex combustor. The time-averaged velocity, root-mean-square (rms) velocity, and flow pattern are compared with the experimental data. And the LES model, RANS BSL k-ω model, and RANS k-ɛ model are also applied for the simulation with different mesh resolutions. The results show that the VLES BSL k-ω model provides improved accuracy for velocity prediction. The classical large vortex structure for the trapped vortex combustor is captured qualitatively by the VLES BSL k-ω model also. In addition, the vortex breakdown and processing vortex cone are visualized using the Q-criterion. Furthermore, the VLES BSL k-ω model is not sensitive to the gird resolution. The VLES method is able to predict the turbulent flow of trapped vortex combustor relatively well.