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(2009) Mark abstract This thesis presents an experimental investigation carried out to study penetration and fragmentation of liquid injected into Mach 6 hypersonic cross flow. Flow topology, shock and vortex systems, fragmentation and atomization mechanisms are investigated using high-speed photography, Schlieren photography, flow visualization and Phase Doppler Interferometry techniques. All experiments are conducted at the H-3 Mach 6 wind tunnel facility of the von Karman Institute. Water is used for all tests. Freestream conditions of air flow are kept constant. The variation of the injector geometry and the effect of momentum flux ratio are studied throughout the experimental campaign. Droplet size measurements are analyzed and treated to characterize the atomization process of the liquid jet. The Sauter Mean Diameter and the standard deviation of the droplet size distribution are calculated and presented as a function of location and momentum flux ratio. The obtained Sauter Mean Diameter distribution is compared with the theory available in the literature for lower cross flow speed cases. The whipping phenomenon observed for the low momentum flux ratio liquid injections is explained by frequency maps, which allow one to see the flow domains with similar frequency content. This analysis proposes that the penetration of liquid jet determines the shape of the bow shock, which determines the location and angle of the separation shock. The separation shock is observed to penetrate into liquid phase, playing an important role in fragmentation of liquid, thus changing the penetration height and the shape of the bow shock. A continuous interaction between the liquid penetration, bow shock, separation shock and liquid fragmentation is believed to be the mechanism responsible of the whipping phenomenon. The fragmentation of liquid exposed to Mach 6 air flow is also investigated. Experiments are conducted using water-filled balloons mounted on sharp and blunt leading edge supports. The water-filled balloons are exposed to Mach 6 air flow and high speed camera measurements are taken during the bursting of the balloon, to study the fragmentation of water. Shock patterns and flow topology are visualized by Schlieren photography.

Please use this url to cite or link to this publication: http://hdl.handle.net/1854/LU-760626



Author: Cem Ozan Asma

Source: https://biblio.ugent.be/publication/760626



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