Localized fluidization in a granular medium: Parametric study with a physical model of “sand boiling”

The present study investigates steady-state localized fluidization within a granular bed by means of experiments on a physical model using a direct internal visualization by means of combined optical techniques. The experimental setup allows access to a broad range of control parameters with the purpose of extending previous findings on this specific configuration, in particular regarding the critical flow rate needed to generate a chimney fluidization. A saturation of this critical flow rate with bed height is and can be explained by a purely hydrodynamic effect related to the geometry and the permeability of the bed which rule together the development of the upward fluid flow through the initially static granular bed. A quantitative model based on CFD simulations is successfully developed in good agreement with the experimental findings.