The commercial software package, FLUENT 17.0 was used to perform the transient numerical simulations of the flow, which was based on the finite volume method. In order to obtain an accurate solution of the mechanical rotation, a steady calculation with multiple reference frame (MRF) was conducted to set initial values, then the transient simulation was performed by using the SM method, which was first proposed by Jaworski and Dudczak23. Interfaces were set between the rotating part and the stationary part. The momentum equations were discretized by the second order upwind scheme, and the coupling between the continuity and momentum equations was realized by using the pressure implicit with PISO algorithm.
Before performing LES simulation, steady-state calculation using k-ε model was carried out to obtain the initial values of the flow field. The transient simulation results by LES were collected after the impeller has achieved a pseudo-stationary state (about 20 s of the real time). The time step size was set to 0.005 s in the present work. For each time step, the residuals drop to below the specified convergence tolerance (10-7) after 100 iterations. The total acquisition time was 50 s, corresponding to 75~100 rotations of the MBC agitator.
Results and discussion