Chemical and Biomolecular Engineering - Theses
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ItemSplashing due to gas injection( 1993)The splash event produced by a falling drop impinging on a bath of liquid was studied to enable a more fundamental understanding of the mechanisms of splash formation. An experimental method involving the use of a high speed photographic technique was developed to enable discrete splash events to be recorded at different time intervals. The effect of varying impact velocity, liquid viscosity and surface tension on the splash event was studied. The aspects of the splash mechanism that pertained to the projection of liquid above the liquid surface were monitored as a function of the experimental variables. Such aspects included the cavity depth, the Rayleigh jet behaviour and the extruded crown behaviour. Depending on the impact velocity of the falling drop, different shaped Rayleigh jets formed which varied in their manner of break up. Such changes in the Rayleigh jet behaviour could be related to the curvature of the interfacial cavity produced by the impact of the falling drop. As the impact velocity increased, the maximum height of the extruded crown increased. If the impact velocity exceeded a critical value, break up of the crown occurred. Increasing liquid viscosity had the effect of dissipating the energy of the system and hence producing less splash. Such viscous dissipating effects were quantified by the use of an energy balance. For liquids of a lower surface tension, there was evidence to suggest that a greater proportion of the incoming energy to the splash event was transferred to the extruded crown rather than to the cavity. Consequently, the splash produced from the break up and extrusion of the crown became more significant. A knowledge of the size of the bubbles reaching the liquid surface would assist in predicting the splashing behaviour of an industrial process which utilised gas injection.