Date of Award

8-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Ochterbeck, Jay M

Committee Member

Tong, Chenning

Committee Member

Xuan, Xiangchun

Abstract

The complete envelopment of a submerged object by a continuous cavity, or supercavity, results in significant reduction of the skin drag acting on the object, allowing for substantial increases in the maximum speeds of underwater devices. The formation of supercavities often requires supplemental ventilation, traditionally by non-condensable gasses, as natural supercavitation occurs at relative speeds between the object and liquid medium that are infeasible for the device to reach without supercavitation itself. The aim of this research is to investigate the feasibility of vaporous ventilation in supercavitation design with the hope of reducing non-condensable ventilation requirements which are inherently limited in their supply for submerged devices. Specifically, the partial or complete replacement of non-condensable gasses with steam for ventilated supercavitation was investigated to determine the effect on cavity development and ventilation requirements. While the use of vaporous ventilation gasses was unfound throughout the extensive literature review, a theoretical analysis which drew from various ventilation scenarios of steam insertion into liquid pools or flows suggested limited potential for the sole use of steam as a ventilation gas. In addition to a theoretical evaluation, cavitator systems were designed and tested to obtain both qualitative and quantitative results. Modest increases in the cavity volume and length were seen for very specific combinations of concurrent ventilation of steam and air relative to air only ventilation. The overall advantages appear extremely limited, however, as the ventilation requirements for steam addition are roughly an order of magnitude larger compared to the required increases of non-condensable ventilation for the production of similar results. Steam alone was shown to be entirely incapable of generating continuous cavitation structures for the range of steam flowrates tested, the upper limit being over three orders of magnitude larger than the critical air ventilation flowrate needed for successful creation of a continuous attached cavity. As such, the advantages of steam ventilation in supercavitation design appear very limited at best when compared to the relative ease of ventilated supercavity development by non-condensable gasses.

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Engineering Commons

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