The spatiotemporal dynamics of segregation-band drift in particle- laden rimming flow
Seminar Room 1, Newton Institute
AbstractWe described a new pattern formation process associated with flow inside a horizontal rotating cylinder that is partially filled with a particle-laden fluid. The pattern is observed to form as the particles segregate and agglomerate to form circumferential bands with high particle concentrations. Any two neighbouring granule bands are separated from one another by regions of liquid with low particle concentrations or, in some cases, regions entirely free of particles. Out most recent experiments have revealed that the system can display an extremely rich, often highly symmetric, spatiotemporal behaviour that emerges over days or weeks as the patterns drift very slowly along the axis of rotation. The plot was assembled by extracating pixel lines from successive photos and composing those into a single figure. The presence of a band is indetified in black whereas regions of low granule concentration are represented in white. It can be seen that the bands drift from location L>0 towards the cylinder end walls at L=0 cm and L= 27 cm. For other experimental conditions bands can drift from the end walls towards the cylinder centre, they may display entirely irregular drift characteristics, or they may not drift at all. We discuss results from long-term observations of the system for different values of the involved relevant physical variables. The key non-dimensional parameters governing the system are identified.
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