Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having hydrofoil
Utility Patent
1997-10-09
2001-01-02
Basinger, Sherman (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having hydrofoil
C114S061120, C114S272000
Utility Patent
active
06167829
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention applies to the field of hydrodynamics, and relates to the use of cavities to reduce the drag of ships, submarines, torpedoes, hydrofoils, surface-piercing struts, propellers, control surfaces, fairings, and in general, to any underwater surface.
Vapor filled cavities for reducing hydrofoil drag were patented by Tulin (U.S. Pat. No. 3,065,723) and Wennegal (U.S. Pat. No. 3,044,432); the latter patent included leading and trailing edge flaps. Low drag base-vented and side-vented hydrofoil concepts were patented a year later by Lang (U.S. Pat. No. 3,109,495). A low-drag submarine was patented by Lee about the same time wherein the speed was so high that a vapor-filled cavity is formed between an adjustable nose cone and a tail section (U.S. Pat. No. 3,041,992). However, that concept would not work because the submarine is in a constant-pressure vapor cavity which would not provide any lift to support the massive weight of a submarine. Control fins are shown, but these would be far too small to support submarine weight, and no teaching was included to use the fins in that manner. A different means for reducing torpedo drag was patented by Eichenberger in which a gas film was used to cover the surface of a torpedo in which the gas film is so thin that it would sustain the outside pressure changes due to depth and provide displacement lift to support the torpedo weight (U.S. Pat. Nos. 3,016,865 and 3,075,489). However, that concept appears to be complex, and would require accurately-machined surfaces. A different means for reducing torpedo drag by using a gas-filled cavity was patented by Lang in which lift is provided by nosepieces and tailpieces to support torpedo weight (U.S. Pat. No. 3,205,846). Claims in U.S. Pat. No. 3,504,649 include a provision for ejecting upper and lower sheets to reduce frictional drag on displacement hydrofoils; also included were air removal means. However, that patent suggests that the air supplied to the upper and lower surfaces comes from the same-plenum, and no mention is made that these air sheets are at different pressures in order to support the vehicle weight. If both air sheets are at the same pressure, one of the air sheets would break up into individual bubbles and lose its ability to reduce drag. Means to reduce thus drag on the lower surface of boats was patented by Baldwin (U.S. Pat. No. 1,656,411). That concept is somewhat like the modern SES (surface effect ship) concept. More recent ways to reduce the drag on boat bottoms have been patented by Burg (U.S. Pat. Nos. 5,176,095 and 5,415,120). A recent patent shows how drag can be reduced on hydrofoils by using a special cross-sectional shape which operates either fully wetted, supercavitating or base-cavitated depending upon speed (U.S. Pat. No. 5,601,047).
Marine vehicles are categorized as either displacement craft or dynamic-lift craft. Displacement craft derive their lift from buoyancy (displacement). Dynamic-lift craft derive their lift dynamically, such as by hydrofoils or planing surfaces. The drag of displacement craft is primarily frictional and wavemaking. The drag of dynamic-lift craft is primarily frictional and induced (drag induced by lift). In high-speed craft of either type, frictional drag is normally more than half the total drag. It is important to reduce frictional drag, although all types of drag are reduced to achieve a large lift-to-drag (L/D) ratio.
The following are dynamic-lift: hydrofoil ships, air cushion vehicles (ACV), seaplanes, wing-in-ground effect (WIG) craft, planing hydrofoil ships, surface effect ships (SES) and ram wing -craft. Displacement craft include: slender monohull ships, catamaran ships, SWATH (Small Waterplane Area Twin Hull) and displacement hydrofoil ships.
The need for reduction in frictional drag has long existed. Means for reducing frictional drag include laminarization, air cavities and air films, riblets, magnetohydrodynamics, microbubble ejection, polymer ejection and moving walls.
The invention provides an air-cavity drag-reducing system, larger-than-normal sweepback on hydrofoils and struts, and control of hydrofoil and strut dynamic forces by controlling their air cavities.
Drag and motion are reduced by factors of 6 or more compared with existing vehicles to transit 10,000 miles at 100 knots without refueling, and to limit vertical accelerations in 30-ft waves to around 0.1 g when either transiting or loitering offshore.
The new vehicles are built using conventional materials, machinery and manufacturing methods.
The benefits of these new vehicles include greatly reduced fuel consumption, longer range, higher speed and greatly improved seakindliness compared with state-of-the-art vehicles.
The new ships deliver a sizable military force almost anywhere in the world within 100 hours. That capability is most important in regions where airfields are unavailable. If immediate action is not required, then these new vehicles have the ability to loiter offshore, show a military presence and sustain troops for one month without resupply. Other military applications include missile launchers, V/STOL or conventional aircraft carriers, arsenal ships and patrol vessels.
Commercial applications include cost-effective ships for rapid delivery of perishable or high-value cargo, fast ferries, commercial fishing vessels and recreational craft. Those applications may be scaled down in size and speed.
SUMMARY OF THE INVENTION
The ship hull is supported above water by seven struts attached to a horizontal V-shaped hydrofoil unit which is swept back 70 degrees. The hydrofoil unit has a span of 261 ft, is optimized to operate at a depth of 22 feet, and consists of three independent, adjacent hydrofoils. The propulsion system uses four ducted air propellers, similar to those used on hovercraft. Alternative propulsors are underwater superventilating propellers and pumpjets. The power plants are either gas turbines or diesel engines, and provide the required 137,000 shp to cruise at 100 knots. To meet the range requirement, drag is reduced on the hydrofoils and struts by covering most of their underwater surfaces with air cavities. The struts and hydrofoils are automatically controlled for maintaining near-constant lift and sideforce to provide a near-level ride in up to 30-ft waves. Maneuvering is achieved by banking the ship into turns. Emergency turns and stops are augmented by lowering drag plates into the water.
The hydrofoil hull has a beam of 100 ft, and an at-rest draft: of 10 ft with hydrofoils retracted. In a preferred embodiment, the three hydrofoil sections retract rearward and upward. The hydrofoils are retracted when offloading onto a beach, when operating in shallow water or harbors, or when transiting the Suez Canal. Also, the hydrofoils automatically retract in a collision with an underwater obstacle. Alternative hydrofoils not only retract but fold against the hull to clear the Panama Canal. Offloading onto beaches with slopes as shallow as two degrees is done through the stern via four 20-ft-wide retractable ramps which are lowered after trimming the ship bow down one degree, and backing into shore. When loitering, the hydrofoils remain below water to help reduce motion, and air bags are attached to the hydrofoils to further reduce motion.
Vehicle weight (i.e., lift, L) is fixed. Reducing drag, D, is identical to achieving a high lift-to-drag ratio, L/D, a nondimensional parameter useful in comparing different kinds of vehicles.
All sources of drag are reduced together with frictional drag to satisfy speed and range requirements. Induced drag is reduced by reducing lift per unit span. Wavemaking drag is reduced by reducing the beam/length ratio of ship hulls, by submerging hulls, or by strategically positioning multiple bodies to reduce the overall wavemaking drag.
To minimize seasickness and permit near-normal working conditions, accelerations are kept below around 0.1 g, and roll and pitch angles are kept below around 10 degrees. Higher accelerations are permissible for short periods, and the r
Basinger Sherman
Creighton Wray James
Narasimhan Meera P.
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