Large eddy simulation of flow in an unbaffled stirred tank for different Reynolds numbers

Abstract

Large eddy simulation of flow in a stirred tank has been carried out for three different Reynolds numbers of 4000, 16 000, and 64 000 using a spectral multidomain method in order to observe the effect of Reynolds numbers on the flow fields. As the Reynolds number increases, each large ring vortex at the upper and lower parts of the tank has been broken up into smaller vortices. With increasing Reynolds number, the ring vortex in the mean field becomes a slightly more oblate and increases in height until it reaches the lid of the tank. The isosurface of swirling strength has been adopted to identify the instantaneous and mean tip-vortex structures. Due to the time-dependent jitter in the position of tip vortices, the time-averaged vortex structure appears to decay much faster. This decay is more rapid with increasing Reynolds number. The increment of the ratio of time and volume-averaged resolved scale dissipation and subgrid scaled dissipation was governed by the linear function of Reynolds number.