Jet Mixing

• "Mixing of two solutions combined by gravity drainage," with K. B. Smith and L. F. Mockros, Journal of Pharmaceutical Science and Technology, 49:132-139, 1995. Several medical therapies require mixing two solutions that are initially in separate containers by draining the solution from one container into the other by gravity through a connecting tube. We studied this jet mixing problem for solutions with different densities using flow visualization and electrical conductivity to measure the quality of mixing. When the more dense solution was drained from the upper container into the less dense solution in a lower container, mixing was very effective because the incoming jet of high density solution entrained low density solution and penetrated to the bottom of the lower container resulting in large vortical structures that enhanced mixing. When the less dense solution was drained into the more dense solution, the mixing was less effective because of stratification. We were able to apply a simple theory to this problem to predict the relative importance of the density ratio, velocity of the incoming jet, and dimensions of the container.

• Current Research: Our experience with jet mixing of parenteral solutions of different densities has motivated further research on jet mixing, an industrial mixing technique for which the most useful prior research occurred in the 1940's. We are using Particle Image Velocimetry and flow visualization to analyze the flow field for a turbulent jet of fluid issuing upward into an upright cylindrical tank containing fluid of a different density. We will determine the effect of the jet Reynolds number, the density difference between the jet fluid and the tank fluid, and the depth of fluid in the tank on the quality of mixing and recirculation in the tank. In another project I am collaborating with Dr. David Eckmann of the Department of Anesthesia, to examine the flow of a laminar jet along the axis of a dead-end tube using Particle Image Velocimetry and flow visualization. The physics of the flow are related to mechanical ventilation of the lungs.