Effect of baffles on the flow hydrodynamics of dual-Rushton turbine stirred tank bioreactor—a CFD study

In this research work, numerical simulations were conducted to examine the effect of baffles on flow activity in a stirred tank bioreactor fitted with two six-blade Rushton turbines, at Reynolds number (Re) = 40,000. The lattice Boltzmann method (LBM) was used as a numerical technique to discretize the flow domain. Large Eddy Simulation (LES) method was applied for turbulence modeling. The small-scale turbulent structures were resolved by using the conventional Smagorinsky subgrid-scale (SGS) model. The action of the reactor components (i.e., cylindrical wall, baffles, shaft, and Rushton turbines) on the flow field were obtained by using the immersed boundary (IB) method. The simulations were performed for three different geometries of stirred tank reactors, differentiated based on the impeller clearance. The study shows the impact of baffles on all the three employed geometries. For each of the geometries, simulations were performed with and without the baffles. A uniform, cubic computational grid of 1503\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$150^{3}$$\end{document} lattice nodes was constructed for the simulation. The computer code was developed for performing the simulation. The complexity of the geometry and different physical processes involved make the simulation more challenging and time-consuming. Thus, to get the results in an adequate time, the computer code was parallelized to run on a multicore Graphical Processing Unit (GPU) platform. The results are demonstrated in the form of phase average flow velocities as well as in turbulent properties, with validation from the available experimental data reported in the literature.