Sediment motion induced by Faraday waves in a Hele-Shaw cell.

Abstract

The interaction between the oscillatory boundary-layer flow induced by Faraday waves and a sedimentary granular layer was studied in a Hele-Shaw cell vertically vibrated. The experimental parameters were the vibration frequency f and acceleration a and the particle diameter d_{p}. At a critical value for the depth of the supernatant fluid layer Δh_{c}, a transition between a flat motionless granular layer and a second regime in which the granular layer undulates and oscillates periodically was observed. For the smallest value of d_{p} (for which the Stokes number was St≪1) the reduced acceleration Γ=a/g (g is the acceleration of gravity) is independent of Δh_{c}, while for the larger ones, Γ depends linearly on Δh_{c}. Finally, it is shown that at the onset of grain motion, the wave velocity V_{w}=h_{w}f/2 (h_{w} is the wave amplitude) depends linearly on Δh_{c} and is independent of d_{p}.