Numerical evaluation of turbulent flow structures in a stirred tank with a Rushton turbine based on scale-adaptive simulation

The turbulent flow field generated in a baffled stirred tank by a Rushton turbine impeller is numerically performed by solving the unsteady Reynolds-averaged Navier-Stokes equations. The numerical results are compared with measurements in terms of time-averaged velocity distribution and turbulence characteristics at different locations in the axial and radial directions. The scale adaptive simulations (SAS) turbulence model is used to provide detailed flow information and resolve the large turbulence structures. The three-dimensional nature of the trailing edge vortices generated in the wake region near the impeller trailing edges were well predicted. Evaluation of Reynolds stresses shows the high anisotropy of the turbulence inside the vessel. The unsteadiness and pulsating behaviors within the vessel are clearly captured in the time/space domains in the axial and circumferential directions. The spectral analysis of pressure fluctuation shows the blade passing frequency as the main source of unsteadiness in the turbulent flow within the vessel.