Flow of a concentrated suspension through an abrupt axisymmetric expansion measured by nuclear magnetic resonance imaging

The objective of this work is to characterize the parameters affecting the particle concentration distribution and flow field of a concentrated suspension undergoing steady flow in an abrupt axisymmetric 1:4 expansion. Of particular interest are the relationships between imposed operating conditions and the resulting spatial particle distribution and the interaction between particles and recirculating flow regions. Experiments were conducted to determine the effect of the bulk particle volume fraction, tube-particle radius ratio, and Reynolds number on observed concentration and flow patterns. Particle concentration and velocity profiles were measured by using nuclear magnetic resonance imaging. Results indicate that inlet concentration profiles formed in the upstream narrow tube greatly influenced behavior downstream, more so than direct interparticle collisions in the abrupt expansion. Also, particle depletion in recirculating flow regions was observed under all conditions studied and is consistent with...

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