Using a multiscale model based on the variable interval time average method and a set of averaged equations for incompressible turbulent flows, we simulate the three-dimensional separated and reattaching flow over a swept backward-facing step. The results show that the reattachment length and vortex structure vary with the swept angles from 15° to 60° through a detailed study about velocity profile and pressure distribution. Generally the reattachment length and span wise vorticity decrease dramatically after =30°. The result fully accord with experimental data. Results show that this model is suitable for separated flows, and accurately predict the flow field, so this model should be useful in engineering application.
We designed a kind of swirler to produce strong vortex which was inspired by tornado . Focusing on the velocity and pressure distribution of inlet flow within the swirler, we also conducted a series of numerical simulations on the swirler when we set geometric inlet conditions at the bottom ,middle and top of the swirler. The simulation results showed :1 When the geometric inlet condition was set in the middle of the swirler, it would produce the strongest magnitude of vorticity and the highest vacuum degree in the center of vortex compared with other two places.2When we set the geometric inlet condition at the middle of the swirler, it would create reversed swirl flow. We discovered that such kind of reversed swirl flow would enhance the magnitude of main swirl flow vorticity.
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