Comparison of turbulent models for baffled stirred tank

Abstract

Fluid mixing in stirred tanks is an extensively researched domain in various process industries. A stirred tank uses an impeller to agitate the fluid, inducing turbulent regions that significantly enhance the mixing process. Understanding the fluid dynamics in an agitated vessel can be achieved through both experimental and numerical methods. The present work utilized Computational Fluid Dynamics(CFD) to analyze flow fields within an agitated vessel. The study focuses on evaluating the effectiveness of various Reynolds Averaged Navier-Stokes(RANS) models to estimate flow characteristics within a stirred tank. The geometry comprises a cylindrical tank stirred by a Rushton impeller at 100 rpm. To enhance mixing efficiency, four baffles are affixed to the lateral surface of the tank, generating recirculating flows. The tank is filled with water up to the top wall to prevent vortex formation. Open-source CFD software, OpenFOAM®, is utilized for performing simulations. The study investigated mean velocity components, power number, Root Mean Square (RMS), and Reynolds stress profiles of the stirred tank. The realizable k - ϵ model exhibited superior performance compared to other RANS models in predicting flow parameters of baffled stirred tanks under specified flow conditions considered in this investigation.