Abstract Summary (Max 250 words)
Estimation of power number and mixing characteristics lab-scale stirred reactors without wall-mounted baffles remains a major challenge in computational fluid dynamics (CFD) because of the complex intimate interaction between impeller-induced flow structures, free-surface deformation, a more or less central precessing vortex, and turbulence. In this study, CFD simulations were performed to evaluate the impact of vortex formation, impeller diameter, and Reynolds-Averaged Navier–Stokes (RANS) turbulence models on power number and mixing characteristics of a 100 mL stirred reactor operating in the turbulent regime at 400 rpm. A four-blade pitched blade turbine (4PBT45) with varying diameters (25 mm, 30 mm, 34 mm, and 38 mm) was analysed as the impeller of the reactor. Comparisons were conducted between two different modelling approaches, SST k–ω and k–ε, to assess their predictive capability for vortex dynamics and fluid flow characteristics. All the simulations are performed using sliding mesh (SM) and the volume of fluid (VOF) method to simulate liquid-air surface. The results demonstrate that vortex formation notably changes flow topology, especially near the free surface and in the impeller discharge region. Larger impeller diameters increased power consumption, but power number decreased with the increase in D/T. RANS models showed very similar power number, vortex depth and flow velocities.
