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Buoyancy-driven destabilization of an immersed granular bed
Published online by Cambridge University Press: 26 March 2018
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 $h$, a time series of the free layer surface is extracted, allowing us to dynamically compute the underlying volume of the granular layer. Different observed phenomena, namely 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 analysed. We show that the phenomenon is mainly driven by heat transfer, for large $h$ and also involves a variable height thermal boundary condition and Darcy flow triggering, for small $h$. Simple modelling with no adjustable parameters not only allows us to capture the observed scaling power laws but is also in quantitative agreement with the obtained experimental data.
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- © 2018 Cambridge University Press
References
Herbert et al. supplementary movie
A typical long-run (total) evolution of the thermal destabilization and grain particles re-suspension of the granular layer, for an initial length h = 23 mm and $\Delta$ = 45 K, showing the different stages of the process. Note that the movie time is accelerated: 1 s in the movie corresponds to 12.5 s in physical time.
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