Rayleigh-Taylor instability in a sedimenting suspension

The temporal evolution of an interface between glycerin and a glycerin-sand suspension of small packing fraction (obtained using the hindered settling phenomenon) driven by gravity is experimentally investigated. The growth rates for the different wave numbers characterizing the developing front are determined by means of a Fourier analysis. To model the observed behavior, we apply the idea of the Rayleigh-Taylor instability for a homogeneous fluid with vertically varying density and viscosity (one-fluid model). A good agreement between the experimental and theoretical results is obtained.