US3155066A

US3155066A - Ship stabilizer

Info

Publication number: US3155066A
Application number: US184719A
Authority: US
Inventors: Sheldon B Field
Original assignee: John J Mcmullen Associates Inc
Current assignee: John J Mcmullen Associates Inc
Priority date: 1962-04-03
Filing date: 1962-04-03
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03

Description

Nov. 3, 1964 s. B. FIELD 3,155,066

SHIP STABILIZER Filed April 5, 1962 INVENTOR. 8051.00 8. HELD United States Patent M 3,155,066 srm STABILEZER Sheldon l3. Field, Floral Park, N.Y., assignor to John J. Mcltiullen Associates, Inc., a corporation of New York Filed Apr. 3, 1962, Ser. No. 184,719 4- Clahns. (Cl. 114-125) The present invention relates generally to ship stabilization and more particularly to an improved apparatus for applying a restoring moment to a ship by the movement of fluid within a tank.

Ships of practically every type encounter the problem of undesirable ship motion caused by the surface condition of the water. Depending upon the type and size of the ship and the operating conditions to which the ship is to be subjected, various hull designs are selected to counteract the tendency of the water to impart motion to the ship. Due to the great number of variables present and since cyclic wave motion can cause a gradual increase in the energy of motion of the ship, hull design provides only a limited effect in controlling the ship motion. Other attempts to minimize ship motion in response to wave action include the provision of stabilization systems which are capable of applying a restoring moment to the ship when it is subjected to the motion. Particular emphasis has been made with respect to improving systems for minimizing roll. Ballast tanks connected by piping and the like have been employed in order to transfer water in a manner to generate a restoring moment. Such systerns encounter the ditiiculty of maintaining the proper phasing between the restoring moment and the motion imparted to the ship. Efforts to employ volumes of air above liquid ballast for controlling the ballast have resulted in massive systems which were uncertain as well as excessively noisy in operation. Efforts have also been directed to providing the slip with fixed or movable fin members extending from the hull beneath the waterline and adapted to generate restoring moments from the hydrodynamic forces on the fins accompanying the motion of the ship. In certain applications controlled fins have been effective in controlling the roll of the ship but only with the expense of complex systems employing massive fin members and operating machinery. Furthermore, controlled fins which are generally effective only when the ship is under way with sufficient speed cause drag resulting in a loss of ship speed.

in the past, stabilization systems have been primarily used in ships in which it is desired to have stabilization only when the ship is under way. The problem of stabilizing a stationary ship now however is of greater importance. For example ships carrying radio equipment for aircraft navigation purposes are conventionally required to be maintained on station in the mid-ocean for extended periods of time. Such ships may be maintained at a stationary point or operated at low speed about a stationary point. In defense systems radar picket ships, which again operate at a predetermined station, are em ployed to carry early warning radar equipment at extended distances from land. In the development of missile devices and space vehicles, it is necessary to maintain great numbers of ships on station throughout the oceans of the world in order to track and monitor the flight path and operation of these devices. It is obvious that without a sufiicient degree of stabilization the equipment carried by any of these ships can be interfered with by excessive ship motion and rendered practically ineffective during a heavy sea condition.

Accordingly it is the primary object of the present invention to provide a ship stabilizer which is capable of applying a restoring moment to the ship whether the ship is under Way or stationary.

3,155,065 Patented Nov. 3, 1964 More particularly, it is an object of the invention to provide a ship stabilizer which is passive, that is a stabilizer which applies the restoring moment directly in response to the movement of the ship about the axis about which the ship is to be stabilized without the need of control equipment.

Furthermore, it is an object of the invention to provide a ship stabilizer in which the movement of fluid in re sponse to the movement of a ship is sufficiently opposed in order that the fluid can apply a restoring moment to the ship.

Another object of the invention is to provide a ship stabilizer which is passive in operation but which is adapted to be conveniently adjusted to compensate for changes in the condition of the ship or the sea.

A still further object of the invention is to provide a ship stabilizer which is relatively compact and of reason able weight.

In one embodiment of the invention the ship stabilizer comprises a tank containing a quantity of fluid having a free surface. The longitudinal axis of the tank is adapted to extend substantially horizontally and substantially at right angles to the axis about which the ship is to be stabilized. Thus if the ship is to be stabilized against roll, the tank is disposed in a substantially athwartship direc, tion along one of the decks of the ship. In order to oppose the flow of liuid from one end portion of the tank to the other in response to the movement of the ship, spaced apart vertically disposed plates are located within the tank parallel to its longitudinal axis. The plates provide a plurality of iiow paths for the fluid in moving from one end portion or" the tank to the other. The plurality of paths oppose the flow of the fluid and cause a restoring moment to be applied by the weight of the fluid to the ship.

In another embodiment of the invention, vertical bafiles are disposed at an angle to the longitudinal axis of the tank and extend along a portion of the tank adjacent to the end portions thereof. This arrangement increases the path of flow between the end portions of the tank and thereby opposes the how between the end portions.

In still another embodiment of the invention, the vertical cross-section of the level of fluid adjacent the baflles is substantially equal to the cross-section of the level of fluid in the end portions of the tank.

In a further embodiment of the invention curved vertical bafies disposed within the tank increase the path of the flow of the fluid from one end portion of the tank to the other and thereby oppose the flow of fluid so that a restoring moment is applied to the ship.

Other objects and features of the invention will become apparent in the following specification and claims and in the drawings in which:

FIG. 1 is a vertical section view showing the stabilizer extending across the beam of a ship below decks;

FIG. 2 is an enlarged plan view of the stabilizer show ing the tank containing a plurality of baffles disposed along its length;

FIG. 3 is an enlarged perspective view of the stabilizer of the invention;

FIG. 4 is an enlarged fragmentary plan view of the stabilizer showing a plurality of curved bafiles.

In FIG. 1 an embodiment of the invention is shown and is referred to generally by the reference numeral lit. in FIG. 1 stabilizer it? is shown disposed in an athwartship direction below main deck 11. With this arrangement stabilizer 1% extends substantially from one side to the other of hull 12 and provides stabilization against roll. The stabilizer includes an elongated tank formed by sides 13 and 14' and

ends

15 and 16. By extending the stabilizer across the hull the maximum moment arm for the liquid can be obtained. The stabilizer is proportioned in a manner such that the weight of liquid displaced to a position adjacent an end portion thereof is suiflcient to generate a restoring moment capable of opposing the motion'of the ship for a range of sea conditions. The fluid within the tank has a free surface so that it can move in response to the motion of the ship.

Plates 17 are spaced apart from one another and disposed in a vertical manner withinthe tank parallel to its longitudinal axis which lies in an athwartship direction. The plates form a plurality ofpassages connecting end portion or chamber 13 adjacent end 15 with end portion or chamber 19-adjacent end 16. Thus the stabilizer comprises a pair of end portions connected by a central portion which is divided into a plurality of passages by the plates. The passages formed by the plurality of plates cause fluid friction with respect to the flow of liquid and thereby oppose the flow of liquid from one end portion of the tank'to the other. The opposing of the movement of the liquid results in it applying a restoring moment to the ship.

Baflles

20 and 21 have a flattened if-shape or chevronform in the plan view are attached to the end of the plates adjacent end portions 18 and 19 and are installed in the

sides

13 and 14 of the tank. The batfles provide additional surfaces to increase the resistance to flow when the fluid attempts to pass from one end portion of the tank'to the other. Besides increasing the fluid frictional force, the shape of the baflies increases the flow path and thereby provides an additional opposing force to the flow of fluid from one end of the stabilizer to the other. Since the bafiies and plates have a proportionally narrow'transverse section, as shown in Flu. 2, the cross-section presentedto theflow of fluid is substantially constant in the end portions of the stabilizer as well as in the regions between the batfles and the plates. This arrangement permits a stabilizer of minimum dimensions to contain a maximum quantity of fluid.

The fluid to be employed within the stabilizer can be any liquid or the like having suflicient density and with a viscosity of a sufliciently low magnitude so that flow can readily take place between the baflies and the plates. Liquids such as sea water, fresh water, bunker oil or types of liquid cargo can be used in the stabilizer tank. Once the stabilizer has been designed and installed within the ship, the variable of the depth of fluid within the stabilizer is available as the means for tuning the stabilizer to various conditions of the ship and the sea.

In order for a restoring moment to be generated, it is necessary that the moment be substantially out of phase with the forces applied to the ship by the sea. Thus in the caseof roll as the crest of a wave strikes along one side of the ship, the force resulting from the moment must be applied in opposition to the force of the wave. After the wave causes the ship to roll, it is necessary that the moment be reversed so that force is applied to the opposite side of the ship.

In operation the movement of fluid within the stabilizer provides the restoring moment with the proper phase relationship to the forces applied to the ship which are causingthe disturbance. For an example, if waves tend to elevate the side of the hull adjacent end portion 18, the fluid within the end portion provides a moment opposing the elevation of this side of the hull. As the hull rises, the passages formed'by the batiles and plates oppose the flow of fluid from end portion 18 in the direction of end portion 19. At the high point of the upward movement of the side of the ship adjacent end portion 18, a hydrostatic head is formed within the stabilizer so that flow passes in the direction of end portion 19. The potential energy of the hydrostatic head is maximum at the maximum elevation of the hull adjacent end portion 18. The potential enercy of fluid adjacent end portion 18 is converted into kinetic energy as the fluid flows in a direction of end portion 19. As the ship passes through a levelposition the fluid continues to flow in the direction of end portion 19 due to its kinetic energy. In this way it is seen there is an accumulation of fluid in end portion 19 as the portion of the hull adjacent thereto attempts to be elevated by the sea forces. Again during this process the arrangement of bafiles and plates retards an immediate reversal of flow so that the fluid can present a restoring moment to the hull. This process then continues so long as sea forces are applied to the hull'to cause it to move about the roll axis of the ship.

It should be understood that the angle between theelements of battle Ztl can be varied and that the line of juncture between-the elements may be a sharp corner or a radius bend. As shown in FIG. 4, baffles 2-2 can also be provided with a substantially curved horizontal crosssection. In addition the number ofplatesemployed in the stabilizer may also be varied. The arrangement of plates and bafiles provides suiiicient damping of the fluid within the tank so that it is insured that'the stabilizer operates in a proper manner without any tendency to destabilize at non-resonant frequencies imparted to'the huh by the sea.

It should be further understood that the stabilizer is adaptable for stabilization of other axes of a ship. Furthermore, the stabilizer is not limited to ship installations but can be employed with other vehicles or platforms that are subject to disturbances of the supporting medium.

While there has been disclosed what at present are considered to be preferred embodiment of the invention, it is to be understood that changes and modifications can be made therein without departing from the essential spirit of the invention. It is intended therefore in the appended claims to cover all such changes and modifications within the true scope of the invention.

I claim:

1. A ship stabilizer comprising an'elongated containing means for holding a fluid in a free surface condition in all parts of said containing means, the longitudinal axis of said containing means extending at right angles to the ship stabilizing axis, a plurality of elongated bafllc means disposed vertically in said containing means transversely spaced apart with respect to the longitudinal axis of said containing means, said baflle means defining a plurality of transversely spaced fluid passageways which act on said fluid to produce a substantial dissipation of energy from said fluid as it flows through saidpassageways responsive to oscillation of said ship about its stabilizing axis, at least one of said passageways having a substantially constant transverse dimension along all points thereof, and wherein said bafi'le means define a plurality of tortuous passageways for changing the flow direction.

2. A ship stabilizer comprising an elongated containing means for holding a fluid in a free surface condition at all parts of said containing means, the longitudinal axis of said containing means extending at right angles to the ship stabilizing axis, a plurality of elongated baflie means disposed vertically in said containing means transversely spaced apart with respect to the longitudinal axis of said containing means, said batfle means defining a plurality of transversely spaced fluid passageways which act on said fluid to produce a substantial dissipation of energy from said fluid as it flows through said passageways responsive to oscillation of said ship about its stabilizing axis, at least one of said passageways having a substantially transverse dimension along all points thereof, and wherein said baifle means extend for a substantial distance longitudinally in said containing means and terminate spaced from the ends of said containing means, and wherein the end portions of said baflie means are deformed to define tortuous flow paths.

3. A ship stabilizer comprising a rectangular tank to be partially filled in a free surface condition with a fluid, said tank adapted to be positioned horizontally and at right angles to the ship stabilizing axis, and a plurality of parallel spaced plates mounted from bottom to top along the long axis of said tank, said plates defining a plurality of fluid passageways, at least one of said passageways having a substantially constant transverse dimension at substantially all points thereof, and wherein the end portions of said plates are deformed to a V shape.

4. A ship stabilizer comprising a rectangular tank to be partially filled in a free surface condition with a fluid, said tank adapted to be positioned horizontally and at right angles to the ship stabilizing axis, and a plurality of parallel spaced plates mounted from bottom to top along the long axis of said tank, said plates defining a plurality of fluid passageways, at least one of said passage- Ways having a substantially constant transverse dimension at substantially all points thereof, and wherein the end portions of said plates are deformed to a radius bend.

References Cited in the file of this patent UNITED STATES PATENTS 3,054,373 Ripley Sept. 18,

3,083,673 Ripley Apr. 2,

FOREIGN PATENTS 435,100 Great Britain Sept. 13,

655,073 Germany Jan. 7,

688,796 Germany Mar. 2,

OTHER REFERENCES 1943, now abandoned.