Buoyancy-driven destabilization of an immersed granular bed

Abstract

Under suitable conditions, an immersed granular bed can be destabilized by local thermal forcing and the induced buoyant force. The destabilization is evident from the triggering and establishment of a dense fluid-like granular plume. Varying the initial granular layer average height h, time series of the free layer surface are extracted, allowing us to dynamically compute the underlying volume of the granular layer. The initial interface deformation, the lowering of the average granular interface (i.e. decrease of the granular layer volume) and the emission of a plume are observed and analyzed. We show that the phenomenon is mainly driven by heat transfer, for large h and also involves variable height thermal boundary condition & Darcy's flow triggering, for small h. Simple modeling with no adjustable parameter not only allows us to capture the observed scaling power laws but is also in quantitative agreement with the obtained experimental data.

An investigation of granular material movement due to instability post impinging upward fluid

“…Settling velocity is influenced by the drag coefficient and Reynolds number [26]. The analysis shows that the destabilization of the submerged bed depends primarily on the initial stabilizing density contrast when the grains are heavier than the surrounding liquid [27].…”

Fluid-particle suspension by gas release from a granular bed

“…To tackle this question, we consider particle entrainment immersed granular beds. The resuspension of particles forming this solid-like settled state and the induced erosion, chimney or crater formation have been investigated using different mechanisms such as shearing flow [14,15], the impact of liquid jets [16][17][18][19], thermal convection or plume emission [20][21][22][23][24], underground cavity collapse [25], fluidization [26], etc. The present paper focuses on gas release from a granular bed, a scenario highlighted in the above applications.…”