PIV experiments and LES modeling of non-Newtonian fluids in laboratory and pilot-scale stirred tanks

Abstract Detailed information on local flow structure is essential for optimizing the mixing processes of stirred tanks. Computational fluid dynamics techniques can be reliable for predicting the 3D instantaneous flow structures after validating them against experimental results. In this study, Stereoscopic Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES) modeling were used to investigate the 3D instantaneous flow fields of non-Newtonian fluids. The effects of scale-up on mixing process was studied by operating a laboratory (15 L) and pilot-scale (50 L) stirred tanks. The 3D instantaneous velocity field components, turbulent kinetic energy, and turbulent dissipation rate were calculated considering the effects of fluid rheology and impeller speeds. The LES model performed best at lower Reynolds numbers, effectively capturing flow patterns in regions with less intense turbulence. The deviation between predicted results from the LES and PIV data was largest in the 50 L tank. Higher impeller speeds assisted the mixing process by reducing the stagnant zones in the bulk of the tank.