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arXiv · 1607.07774

Giant drag reduction due to interstitial air in sand

Tess Homan·Devaraj van der Meer
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Abstract

When an object impacts onto a bed of very loose, fine sand, the drag it experiences depends on the ambient pressure in a surprising way: Drag is found to increase significantly with decreasing pressure. We use a modified penetrometer experiment to investigate this effect and directly measure the drag on a sphere as a function of both velocity and pressure. We observe a drag reduction of over 90% and trace this effect back to the presence of air in the pores between the sand grains. Finally, we construct a model based on the modification of grain-grain interactions that is in full quantitative agreement with the experiments.

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Tess Homan, Devaraj van der Meer. 2016-07-26. Giant drag reduction due to interstitial air in sand. https://arxiv.org/abs/1607.07774

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