Numerical Analysis of the Hydrodynamics of Proximity Impellers using the SPH Method

Mixing is a critical operation in numerous industrial processes, traditionally performed in agitated tanks to ensure homogenization. Despite its importance, the design of tanks and impellers is often neglected during agitation system selection, resulting in excessive energy consumption and inefficient mixing. To mitigate these challenges, Computational Fluid Dynamics (CFD) serves as a powerful tool for analyzing tank hydrodynamics and quantifying mixing times. CFD employs mathematical models to simulate mass, heat, and momentum transport phenomena within fluid systems. Among the latest advancements in modeling stirred tank hydrodynamics is Smoothed Particle Hydrodynamics (SPH), a mesh-free Lagrangian approach that tracks individual particles characterized by properties such as mass, position, velocity, and pressure. SPH provides significant advantages over traditional mesh-based methods by accurately capturing fluid behavior through particle interactions. In this study, the performance of three impellers�double ribbon, paravisc, and hybrid�was evaluated based on hydrodynamics and mixing times during the homogenization of water and ethanol in a 0.5 L stirred tank. The tank and impellers were meticulously designed, operating at 70% capacity, with the fluids exhibiting the following rheological properties: ?1 = 1000 kg/m�, ?2 = 789 kg/m�, �1 = 1E-6 m�/s, and �2 = 1.52E-6 m�/s. The simulations were conducted under turbulent flow conditions (Reynolds number of 10,000) for a duration of 2 minutes using the DualSPHysics software. The stirring speed was set at 34 rpm, and the initial particle spacing was configured to 1 mm, generating 270,232 fluid particles and 187,512 boundary particles representing the tank and agitator. The analysis included velocity profiles, flow patterns, vorticity, divergence, and density fields to assess mixing performance. The Q-criterion was employed to discern the dominance of rotational or deformational motion and to identify stagnation zones. The results revealed that the double ribbon impeller exhibited superior performance, achieving 88.28% mixing within approximately 100 seconds, while the paravisc and hybrid impellers reached mixing efficiencies of 12.36% and 11.8%, respectively. These findings underscore the potential of SPH as a robust computational approach for linking hydrodynamic behavior with mixing efficiency and identifying key parameters to optimize mixing processes.