3D flow simulation of a baffled stirred tank for an assessment of geometry simplifications and a scale-adaptive turbulence model

Flow simulations are performed on single-phase flow in a baffled tank stirred by a Rushton turbine at a Reynolds number of 40000. The flow physics are discussed, and the benefits of a scale-adaptive simulation (SAS) compared with classical unsteady Reynolds-averaged Navier-Stokes (URANS) models are high-lighted. The effect of geometry simplifications, i.e., infinitely thin blades, is illustrated. Furthermore, due to the existence of low-frequency flow instabilities, the necessity of utilizing a full 360 degrees computational domain and the consideration of up to 150 impeller revolutions in the simulation is demonstrated. By a zonal grid refinement within the blade and wake region, the successively resolved portion of the turbulent spectrum is investigated. Even on computational grids typically employed for URANS simulations, the SAS shows a considerably improved prediction of mean velocity and turbulence statistics, compared with conventional URANS models, and should thus be preferred, e.g., to an under-resolved large eddy simulation (LES). (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study on single-phase flow in a baffled tank stirred by a Rushton turbine at a Reynolds number of 40000 highlighted the benefits of a scale-adaptive simulation (SAS) compared with classical unsteady Reynolds-averaged Navier-Stokes (URANS) models. The necessity of utilizing a full 360 degrees computational domain and the consideration of up to 150 impeller revolutions were demonstrated due to the existence of low-frequency flow instabilities. The SAS simulation showed a considerably improved prediction of mean velocity and turbulence statistics compared with conventional URANS models.