Investigating Using Oscillating Jets for Fluid Mixing

Scaled mixing experiments were conducted to evaluate maintaining mobilized particles in a uniform suspension (the condition of concentration uniformity) using jet pumps to mix the suspension. The study experimentally evaluated uniformity in a 1/12-scale experiment varying the Reynolds number, Froude number, and gravitational settling parameter space. The product of the jet exit velocity and nozzle diameter (U0D0) was used to scale the experimental conditions. The test matrix included a full factorial test between 100% and 50% U₀D₀ and two half-factorial tests at 75% and 25% U₀D₀. Evaluating points at 75% U₀D₀ and 50% U₀D₀ allowed evaluation of curvature. Eliminating points at 25% U₀D₀ decreased the testing time by several weeks. Test conditions were achieved by varying the simulant viscosity (μ), the mean particle size (d_p), and the jet nozzle exit velocity (U₀). Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time ultrasonic attenuation probe and discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (< ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless groups. The two parameters that best describe the maximum solids volume fraction that can be suspended in a double-shell tank were found to be 1) the Froude number (Fr) based on nozzle velocity (U₀) and tank contents level (H) and 2) the dimensionless particle size (d_p/D₀). The dependence on the Reynolds number (Re) does not appear to be statistically significant.