The flow driven by a rotating impeller inside an open fixed cylindrical cavity is studied numerically using the code BLUE, a solver for massively parallel simulations of fully three-dimensional multiphase flows. The impeller is composed of four blades at a 45 degree inclination all attached to a central hub and tube stem. In BLUE, solid forms are constructed by means of a module for the definition of immersed objects via a distance function that takes into account the object’s interaction with the flow for both single and two-phase flows. This distance function is positive in the fluid phase and negative in the solid and we use a moving frame technique for imposing translation and/or rotation.

Fig. 1: Interface shape for f = 5, 7.5 and 10Hz

The variation of the Reynolds number, the clearance and the aspect ratio (interface height versus the tank radius) will be considered in this study but we will highlight the importance of the confinement ratio (blade radius versus the tank radius) in the mixing process. BLUE is wholly written in Fortran 2003 and uses a domain decomposition strategy for parallelization with MPI. The fluid interface solver is based on a parallel implementation of a hybrid Front Tracking/Level Set method designed to handle highly deforming interfaces with complex topology changes. Parallel GMRES and multigrid iterative solvers are applied to the linear systems arising from the implicit solution for the fluid velocities and pressure in the presence of strong density and viscosity discontinuities across fluid phases.

Fig. 2: Interface shape and velocity field for f = 5 Hz

Fig. 3: Interface shape and velocity field for f = 10 Hz