Success and breakdown of Tanner's law for drops of dense granular suspensions

The spreading of viscous droplets of density-matched suspensions on a solid surface is experimentally investigated at the global drop scale.

First, the spreading dynamics still obeys Tanner's law provided one uses an effective viscosity which happens to be smaller than the bulk viscosity of the suspension.

Then, when the height of the drop is of the order of the particle spacing, Tanner's law breaks down as the particles start to freeze and the pure fluid drains out of the solid matrix.