

@mastersthesis {6716,
	title = {Dynamics and noise emission of vortex cavitation bubbles},
	year = {2006},
	note = {3208440},
	school = {University of Michigan},
	type = {phdPh.{D}.},
	address = {Ann Arbor},
	abstract = {The dynamics and noise emission of cavitation bubbles forming within the core of a single line vortex were examined experimentally and numerically. For the experiment, a steady line vortex was formed downstream of a hydrofoil mounted in the test section of a re-circulating water tunnel, allowing for the detailed examination of the growth, splitting and collapse of individual cavitation bubbles as they experience a reduction and recovery of the local static pressure. The average Reynolds number of the vortices was ReΓ = 250000, and the average core radius was 4.5 mm. The growth and collapse of bubbles with maximum aspect ratios of 60 were examined. The acoustic emissions from the bubbles were detected during growth, splitting and collapse. The impulse produced upon collapse was the strongest and usually 10 times the rarely detected impulse caused by inception and splitting. However, the impulse produced by the elongated bubbles was 100 times less than the impulse produced by near-spherical cavitation bubbles. The equilibrium radius of elongated vortex cavitation bubbles are related to the original vortex properties and the local static pressure. The observed bubble radii were between 10\% and 15\% of the original vortex radius. The analytically calculated bubble radii are nearly 3 times larger, even after considering the influence of the cavitation bubble on the original vortex flow field. Similar results were found after direct simulation of the axisymmetric bubble dynamics with DF\_UNCLE{\textcopyright}. These differences are ascribed to the three-dimensional and wavy interfaces of the experimentally observed bubbles compared to the assumption of axisymmetry used in the calculations. The growth and collapse of individual axisymmetric cavitation bubbles were performed to study scaling effects, and the process of bubble splitting. Finally, cavitation inception related to the interaction of two counter-rotating vortices was experimentally examined. In traditional vortex cavitation scaling, the strongest ("primary") vortex is expected to cavitate first. However, vortex interactions can lead the stretching of a weaker ("secondary") vortex as a result of Crow-like instabilities. The weaker vortex can then have a substantially reduced core pressure and incept before the primary vortex.},
	keywords = {0548:Mechanical engineering, Applied sciences, Bubbles, Cavitation, Mechanical engineering, Noise, Vortex},
	url = {http://search.proquest.com/docview/305304270?accountid=14270},
	author = {Choi, Jaehyug}
}
