eXperiment: Suspension Instabilities
Primary Objective(s):

Fluid mechanics and suspension dynamics.

Secondary Objective(s):

Introduction to video acquisition and image analysis.


A non-colloidal suspension of spherical particles in a high-viscosity silicone oil is added to a horizontal cylinder so that the cylinder is only partly filled. The suspension is initially homogeneous, but particles sediment and then migrate, as the cylinder rotates, to form alternating bands of high and low concentration across the length of the cylinder. Band separation and time for band formation depend on rotation rate, particle size, particle-fluid density difference, suspending fluid viscosity, volume fraction, fill fraction, and cylinder length.

Students investigated the effects of fill fraction and cylinder length on band separation and time for band formation.