Simulation of Jet Agitation in Sprayer Tanks: Comparison of Predicted and Measured Water Velocities

Abstract

FLUENT, a computational fluid dynamics program, was used to investigate flow movements in sprayer tanks with hydraulic jet agitators. Two- and three-dimensional simulations were carried out utilizing single-phase (liquid phase only) and multiphase (solids particles in liquid) models. Earlier experimental studies of agitation effectiveness identified important factors affecting agitation effectiveness. This study was initiated to evaluate simulation as a tool in sprayer agitation system design. Interpretations of the flow field predictions supported previous measurements that determined system pressure to be the most influential factor on agitation effectiveness due to the direct relationship between pressure and jet velocity. Multiphase predictions of particle deposit amounts at the tank bottom were not feasible due to the computational demand of the model, which was an attempt to simulate three-dimensional turbulent flows with solid-liquid mixtures. Quantitative verification of single-phase simulations was accomplished by velocity measurements using hot-film sensors in a sprayer tank. Velocities were measured at 9 locations within the sprayer tank, and 12 jet agitation simulations were used. There were 118 of the 144 measured velocities within 50% of velocities predicted by FLUENT, and 120 of 144 measured velocities were within 0.2 m/s of predicted values. FLUENT-generated values tended to be greater than measured velocities near the top of the tank, and FLUENT velocities were always less than measured velocities at a position near the center of the tank.