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Air entrainment during impact onto a liquid pool

Hendrix, M.H.W. (2013) Air entrainment during impact onto a liquid pool.

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Abstract:When a mm-sized drop approaches a liquid pool, both interfaces deform before the drop actually touches the pool. The build up of air pressure prior to coalescence is responsible for this deformation. Due to this deformation, air is usually entrained during impact. We quantify the amount of entrained air numerically, using the Boundary Integral Method (BIM) for potential ow for the drop and the pool, coupled to viscous lubrication theory for the air film that has to be squeezed out during impact. We compare our results to various experimental data and find excellent agreement in the amount of air that is entrapped during drop impact onto a pool. Also the impact of a rigid sphere onto a pool is numerically investigated and the air that is entrapped in this case also matches with available experimental data. In both cases of drop and sphere impact onto a pool the numerical air bubble volume Vb that is found is in agreement with the theoretical scaling Vb=Vdrop=sphere ∼ St−4/3 , where St is the Stokes number. This implies a universal mechanism for air entrainment for both impact scenarios, which has been suggested in recent experimental work, but can now be further investigated with numerical results. In addition, experiments have been conducted to infer the dynamics of a thin air film that is entrapped between an impacting drop and a hydrophobic micro structure using high speed color interferometry.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
Link to this item:https://purl.utwente.nl/essays/63416
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