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