The viscosity of an anisopycnic particle-laden thin film under gravitational force is analyzed experimentally in the high volume-fraction concentration limit. The slurry is a mixture of silicone oil of varying background viscosities and polydisperse heavy glass beads of varying size ranges that settle with respect to the fluid. For the high volume concentrations studied (50% < &phi < 56%), the elapsed time versus average front position scales with the Huppert solution [Nature 300(2), 1982]. For very high background viscosities, the particle settling velocity is very slow with respect to the fluid and Huppert’s constant, decreases with increasing concentration. When the background viscosity is decreased, remains relatively constant as the particle density approaches the maximum. This may be the result of a transition from viscous fluid flow to that of a lubricated sliding solid body.

It was predicted by H.E. Huppert in [1] that the momentum of a particle laden fluid flowing down an incline plane can be modeled by the equation:

where is the incline of the slope.
Based on the above equation, it was predicted that some time after the fluid is initially released, the solution takes the form:

This summer we found that Huppert's solution is a good model even for high concentrations of particles. We however found a consistent initial transient in each of our experiments that lasted for about 15 seconds. A theory for this is currently in the works.