Low-drag hydrodynamic surfaces

Inactive Publication Date: 2005-05-26
LANG THOMAS G +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] A primary objective of this invention is to reduce the drag of high-speed hydrofoil craft by forming a closed gas cavity on each side of each

Problems solved by technology

The problem is how to design underwater surfac

Method used

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Embodiment Construction

[0056] In FIGS. 1 and 2, the hull 2 of hydrofoil craft 1 is supported above water by forward strut 4 and two aft struts 5 which are attached to lifting v-hydrofoil 3. The propulsion system consists of engine 7 in each catamaran hull 6 that drives shaft 8 located in duct 9 of strut 5, thereby eliminating drag on the drive shaft. Shaft 8 enters gearbox 11 located inside pod 12 to drive propeller 13. Pre-spin vanes 14 rotate the water flow entering the propeller so that the water flow leaves the propeller without significant rotation, thereby increasing propeller efficiency. This hydrofoil and propulsion arrangement is equally applicable to monohulls, trimarans or other hull shapes, and applies to one or more support struts, engines and propulsors. Each strut can either be swept back, as shown, or unswept, or swept forward. Strut sweep reduces strut spray drag, and reduces strut side force in beam waves. Hydrofoil sweep reduces susceptibility to cavitation, and reduces craft vertical m...

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Abstract

The invention relates to the use of gas cavities to reduce frictional drag on underwater surfaces such as hydrofoils, struts, fins, rudders, keels, propeller blades, ship hulls, underwater bodies, and wetted surfaces in general. Each gas-filled cavity is formed behind a discontinuity in the surface that causes the water boundary layer to separate from the surface. Gas is ejected into a region behind the discontinuity to fill the cavity; the gas can be air. If a cavity is open to the atmosphere, then air can typically fill the cavity naturally without air ejection. Cavities can either be closed or open. A low drag hydrofoil may have a closed cavity on one side, and an open cavity on the other side. For closed cavities, the underlying surface can be shaped to minimize cavity closure drag. Various ways to generate cavities, change hydrodynamic forces, and duct gas internally on hydrofoils and struts with cavities are covered. Different designs of hydrofoil boats, hydrofoil ships and ship hulls that are amenable to drag reduction are presented.

Description

[0001] This invention was made with Government support under DAAH01-96-C-R228, and DAAH01-98-C-R115 awarded by the Defense Advanced Research Projects Agency. The Government has certain rights in this invention.BACKGROUND OF THE INVENTION [0002] This invention applies to the field of hydrodynamics, and relates to the use of gas cavities to reduce the frictional drag of hydrofoil craft, ship hulls and underwater surfaces in general. [0003] Using cavities to reduce frictional drag is covered in U.S. Pat. No. 3,077,173 (1963) and U.S. Pat. No. 3,109,495 (1963) for base-vented and side-vented hydrofoils, U.S. Pat. No. 3,205,846 (1965) for torpedoes, and U.S. Pat. No. 6,167,829 (2001), together with a pending continuation of that patent, for submerged surfaces in general. [0004] The reduction of frictional drag provides basic benefits: power is reduced, and fuel consumption is reduced. These benefits reduce the weight of a vessel, which further reduces power and fuel consumption compared ...

Claims

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Application Information

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IPC IPC(8): B63B1/24B63B1/28B63B1/38
CPCB63B1/248Y02T70/122B63B1/38B63B1/288Y02T70/10
Inventor LANG, THOMAS G.LANG, JAMES T.
Owner LANG THOMAS G
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