Experiments, Simulations and Models of Colliding Particles in a Liquid

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National Science Foundation - Division of Chemical &Transport Systems ? Particulate & Multiphase Processes Program (1415)Proposal Number: 0730284 Principal Investigators: Hunt, Melany Affiliation: California Institute of Technology Proposal Title: Experiments, Simulations and Models of Colliding Particles in aLiquid The proposed work includes experiments, simulations and modeling of particlewall and particle-particle collisions in a viscous fluid. In recent years, Lagrangian models, such as the discrete element model, have been introduced to compute granular flows at the particle level, incorporating size variations, material properties, and interparticle forces. Although these models rely on simplifications of the collisional interaction, the modeling has been successfully applied to a range of industrial and geophysical flows. For liquid-solid flows, there currently is not a similar technique that can be applied widely to debris flows, slurries, and sediment transport problems. The focus of this proposal is to examine particle collisions in a liquid with an emphasis on developing collisional models that can be incorporated into large scale computations.Intellectual Merit:The proposed work consists of four parts that involve a fundamental understanding of the approach and rebound of a particle to another surface. The proposed work consists of the following: (1) investigation of forces involved in the approach and rebound of colliding particles; (2) immersed-boundary simulations of the coupled motion of the particle and surrounding fluid flow, and the incorporation of the boundary condition; (3) experimental measurements of immersed particle chains; and (4) measurements of the fluid motion resulting from particle collisions. The accompanying experiments are designed to guide and validate the model predictions. This proposal focuses on inertial and collisional effects, and involves Stokes and Reynolds numbers greater than one.Broader Impacts:Lagrangian particle models have been used extensively to investigate mixing of pharmaceuticals and tablets, flows of landslides, particle segregation in hoppers, and transport of agricultural products. Currently, there are efforts to extend this Lagrangian technique to include the effects of an interstitial gas. However, there has been less attention directed to using the method to compute flows of liquids and solids, presumably due to the complexity of the liquid-solid interactions and the lubrication forces. Our proposed computational and experimental efforts should be beneficial in developing computational algorithms for a range of problems found in both geophysical and industrial flows.An integral part of this research work is the education students. In prior and ongoing research, the PI has placed a heavy emphasis on the inclusion of student from underrepresented groups, extensive involvement of undergraduate students, and when appropriate, the inclusion of high school students. These students have the opportunity to author technical papers and to present research findings at appropriate scientific meetings. The PI has also presented her research to local schools through community and campus programs.