SLIDING MESH COMPUTATIONAL FLUID DYNAMICS SIMULATION OF A WIDE AND NARROW GAP INLINE ROTOR-STATOR MIXER

Abstract

The FLUENT™ Computational Fluid Dynamics code was used to simulate the flow of water within an inline rotor-stator mixer. Two devices were simulated. Both had identical dimensions, except for the width of the shear gap: 4 mm for the 'wide gap' model and 0.5 mm for the 'standard gap' model. A two-dimensional approximation was used in conjunction with a RANS turbulence model and sliding mesh technique. Simulated turbulence intensities and mass flow rates are more evenly distributed in the standard gap model. Further, turbulence and mean shear levels within the gap are minimal and probably not important for the production of dispersions. The most intense turbulence is near the downstream stator slot wall, and it is due to fluid impingement. For the standard gap model, this region is more focused and of higher intensity. It is concluded that a narrow gap clearance is needed to produce high intensity stagnation flows on the stator teeth. Simulation results are also compared with previously reported measurements acquired via Laser Doppler Anemometry. With respect to mean velocity, qualitative agreement is good. Quantitatively, neither the mean velocities nor turbulence values are well predicted. This discrepancy is believed to be due in large part to leakage flow over the top of the rotor and stator teeth and to the three-dimensional nature of the flow. Future simulations should be carried out in three dimensions using more sophisticated turbulence models. Additionally, algorithms should be developed to decrease computation time by exploiting the periodic nature of rotor-stator flows.