0000000000808107
AUTHOR
Gaetano Gagliano
Direct numerical simulations of creeping to early turbulent flow in unbaffled and baffled stirred tanks
Abstract It has been known for a long time that the fluid flow and several global quantities, such as the power and pumping numbers, are about the same in baffled and unbaffled mechanically stirred vessels at low Reynolds numbers, but bifurcate at some intermediate Re and take drastically different values in fully turbulent flow. However, several details are not yet completely understood, notably concerning the relation of this bifurcation with the flow features and the transition to turbulence. In order to shed light on these issues, computational fluid dynamics was employed to predict the flow field in two vessels stirred by a six-bladed Rushton turbine at Reynolds numbers from 0.2 to 600…
CFD simulations of early- to fully-turbulent conditions in unbaffled and baffled vessels stirred by a Rushton turbine
Abstract Laboratory scale unbaffled tanks provided with a top cover and a baffled tank both stirred by a Rushton turbine were simulated by carrying out RANS simulations. Three different turbulence models were adopted (k- ω SST, k- e and the SSG Reynolds stress model) to predict the flow field and the relevant performance parameters (power and pumping numbers) of the tank operated from early to fully turbulent conditions. CFD results were compared with literature experimental data and DNS simulation results to validate and properly compare the models. In the range of Reynolds numbers investigated, results showed that, for the unbaffled tank, the SSG model based on Reynolds stresses is a bett…