Suspension Dynamics with Inertia: Combined Discrete-Particle Simulation and Constitutive Modeling Investigations

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0853720MorrisThis project addresses flow of suspensions of rigid particles with inertia at the particle scale. Inertia on the particle scale is defined in terms of the Reynolds number based on shear rate, particle radius and kinematic viscosity. Significant particle-scale inertia implies Reynolds number greater than unity. For small particles, this usually implies larger inertia at the macroscopic scale. Consequently, inertial behavior on multiple scales must be considered. Based on the PI's prior simulations verified against experiment and established simulations, the focus of this study is on simulation of particle-laden flows at finite Reynolds numbers, exploring motions of individual particles as well as particle suspensions. The simulations use the PI's recent developments in the lattice-Boltzmann technique, implemented in a parallel computational algorithm. A number of basic flows will be simulated, including periodic simple shear and pressure-driven flow in conduits, all under a range of finite-Reynolds number conditions with varying particle volume fraction. Flow through conduits showing migrations leading to pronounced accumulation at certain locations have been previously observed. Determination of effective properties of suspensions and modeling of their bulk flow is essential to engineering application of these mixtures. Using statistical analysis of the stress and hydrodynamic diffusivity, a continuum model for suspension flow will be developed. Model predictions will be compared against more complex flows, both from simulations and from experiments. The investigation of bulk suspensions is basic to a wide range of applications involving such materials as inks, coatings and cement as well as many naturally occurring flows. By developing discrete-particle understanding which may be used by theorists and modelers, and developing a continuum description directly from the results, this investigation provides guidance and direction on two fronts. Suspension dynamics is a complex topic, involving physics, mathematics and engineering and thus provides excellent training ground for doctoral and undergraduate research students. The project is designed to involve graduate and undergraduate researchers at one of the most diverse research university settings in the world, the City College of New York. Through collaborations with different universities, laboratories, and industries, young researchers will gain exposure to disciplines from biomedical diagnostics (cell sorting) to the delivery of ceramic precursors and cement. The research results will aid in developing a module in an introductory course using hydrodynamic effects for sorting in microfluidic devices.