Hydrodynamic improvements for the DOLPHIN : a surface-piercing semi-submersible AUV

Butt, Mark-Andrew (1999) Hydrodynamic improvements for the DOLPHIN : a surface-piercing semi-submersible AUV. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (6MB)

Abstract

In 1996, the Institute tor Marine Dynamics (IMD) together with International Submarine Engineering Research Limited (ISER) and Memorial University of Newfoundland (MUN) proposed to design and test a 1/2 scale surface-piercing mast for the DOLPHIN semi-submersible vehicle. The proposed mast was required to reduce mast drag, and hence overall vehicle drag, and, to provide improved roll control. To improve vehicle roll control, a new mast was designed with a 25% of chord plain flap over its lower-half and active air ejection over its surface-piercing upper-half. Both methods of roll control were independently tested in the 200m Clear Water Towing Tank at IMD using a 0.516 scale-model of the DOLPHIN. This work was carried out in early 1998. -- This thesis presents and discusses the results obtained from the scale-model tests. Specifically, it was found that the existing mast represented 54% of overall vehicle drag at the deepest operating draft, while the proposed mast represented only 26% at this same draft. With air ejection from the proposed mast, the overall drag at the deepest draft increased slightly to 31%. -- The basic proposed mast configuration (no air, no flap) provided too much vehicle counter-roll. However, with the inclusion of air ejection on the upper-half of the proposed mast, the vehicle roll moment was considerably reduced. In fact, for some tests the vehicle roll moment was effectively reduced to zero. It was also determined that the 25% of chord flap on the proposed mast was adequate in providing vehicle roll control.

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