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89g

Pressure Drop and Flow Evolution of a Concentrated Suspension in an Abrupt Expansion

Tracey Moraczewski, Department of Chemical Engineering, Columbia University, 500 W. 120th Street, MC 4721, New York, NY 10027 and Nina C. Shapley, Chemical Engineering, Columbia University, 500 W. 120th Street, MC 4721, New York, NY 10027.

Our research aims to enhance the fundamental understanding of the flow of a concentrated suspension through an abrupt expansion, which can be encountered in such applications as materials processing or flow in the circulatory system. In this study, suspensions of neutrally buoyant, noncolloidal spheres in Newtonian liquids undergo steady, pressure-driven flow in an abrupt, axisymmetric 1:4 expansion. Nuclear magnetic resonance imaging (NMRI) is used to measure the steady-state particle concentration and velocity profiles, as well as the evolution of the concentration and velocity profiles during start-up. The effects of particle migration on the pressure field in the system are also investigated, and the role of particle and flow properties (e.g. particle volume fraction, particle size, particle and flow Reynolds number, and inlet conditions) is examined. Results from experiments on the flow evolution and pressure field will be presented and compared with existing models.