US3094094A

US3094094A - Passive stabilization system for long period ships

Info

Publication number: US3094094A
Application number: US83092A
Authority: US
Inventors: Ripley Kenneth Clay
Original assignee: John J Mcmullen Associates Inc
Current assignee: John J Mcmullen Associates Inc
Priority date: 1961-01-16
Filing date: 1961-01-16
Publication date: 1963-06-18
Anticipated expiration: 1980-06-18

Description

June 18, 1963 K. c. RIPLEY 3,094,094

PASSIVE STABILIZATION SYSTEM FOR LONG PERIOD sHIPs Filed Jan. 16, 1961 4 Sheets-Sheet l 00 3 It o' i q I: Q Q "I k Q Q 7 40 h "a \K INVENTOR Kennefh 6. Rip/6y BY I I mflw, WM

ATTORNEYS K. C. RlPLEY June 18, 1963 PASSIVE STABILIZATION SYSTEM FOR LONG PERIOD SHIPS Filed Jan. 16. 1961 4 Sheets-Sheet 2 BY Jmfimwgw ATTORNEYS PASSIVE STABILIZATION SYSTEM FOR LONG PERIOD SHIPS Filed Jan. 16. 1961 K. c. RIPLEY Juhe 18, 1 963 4 Sheets-Sheet 3 INVENTOR Kenna/h 0. R/p/ey ATTORNEYS K. C. RIPLEY 4 Sheets-Sheet 4 I INVENTOR Kan/7am 6. /?/',0/6;

BY v

' ATTORNEYS June 18, 1963 PASSIVE STABILIZATION SYSTEM FOR LONG PERIOD SHIPS Filed Jan. 16. 1961 3,094,094 PASSIVE STABILIZATION SYSTEM FOR LONG PERIOD SHIPS KennethClay Ripley, Washington, D.C., assignor to John J. McMullen Associates, Inc., New York, N.Y., a cor-.

of New York Filed Jan. 16, 1961, Ser. No. 83,092 Claims; (Cl. 114-125) poration This invention relates to the stabilization of ships and more particularly to a system for the passive stabilization of ships of relatively low metacentric height.

All ships have a righting moment which is the name applied to the force tending to restore the ship from heel. Mathematically this moment is expressed as the product of displacement, metacentric height and inclination in radians. In large passenger ships,.where passenger comfort is a design consideration of the naval architect, the righting moment is usually small so that the roll frequency is low. Such ships, commonly called tender, as distinguished from stiff,,ships, are not easily excitedby wave action, but control of roll brought about by the type of wave action to which the. ship is susceptible can be quite difficult. This difiiculty is due to the fact that tender ships already have a low metacentric height. Thus, the use of stabilizing water issharply limited because of the resulting increase in free surface area of liquid. Calculations reveal that, by use of passive systems heretofore known to me, the amount of water necessary to stabilize this type ship against roll induced by very long wave length, low amplitude swell, would too much increase the free surface area of liquid and too much depress the metacentric height of the ship.

. It is thereforean object of this invention to provide an improved passive stabilization system characterized by an increase in the moment tending to counteract roll without concomitant increase in free surface area of liquid. This invention therefore constitutes animprovement over my prior inventions in that it makes provision for the passive stabilization of ships of low metacentric height within the design criteria for free surface area of liquid.

It is an object of the present invention so to employ stabilizing water that the maximum moment tending to oppose roll is achieved with a modest surface area of liquid and with an extremely small total volume of liquid.

Other objects and advantages of this invention will be apparent upon consideration of thefollowing detailed description of the embodiment thereof whichwas installed in the S. S. M atsonia wherein:

FIGURE 1 is a profile view of in cut-away the position of the stabilizer of the present invention in the after part of the ship;

FIGURE 2 is a plan view of the stabilizer of the present invention to a scale much enlarged from that employed in FIGURE 1; i

. FIGURE 3 is a view. in section taken on the line 3 -3 ofFIGUREZ;

FIGURE 4 is a perspective view of the stabilizing equipment of the present invention as it would appear looking forward-from a position above and to the right of it, intervening decks being removed for convenience of illustration; and, l t

FIGURE 5 is a similar view except that the viewing position is somewhat below and to the left of the equipment of the present invention.

The M atsonia is 638 feet long and the equipment of the presentinvention which effectsQstabiliza-tion, i.e. the equipinent shown in plan in FIGURE 2 extends but eighteen feet lengthwise of the ship. 'It is located in-the after part of the ship between E and F decks where the width, from free-board to free-board, is approximately 70 feet.

3,094,094 Patented June 18, 1963 The structural weight of the equipment employed in effecting stabilization is trivial, and the quantity of water necessary to effect roll control is only about /3 of 1% of the displacement of the Matsonia. It can be seen there fore that the stabilization of the ship is accomplished with small loss of usuable tonnage and relatively little required space.

'The stabilizer for the Matsomw is comprised of four

wing tanks

10, 11, :12 and 13; tanks 12 and 13 being on the port side of the ship and

tanks

10 and 11 being on the starboard side. Tank 13 is connected by an elongated nozzle 14 to a mixing chamber-15. Wing tank 10 is also connected to the mixing chamber 15 by a nozzle 16 similar in construction to the nozzle 14. Tank 12 is connected by a nozzle 17 to a mixing chamber 18, and a nozzle 19 connects tank 11 also to the mixing'chamber 18.

Nozzle 14 is defined by a series of circular columns 20-23 inclusive. Nozzle 16 is similarily defined by circular columns 2427 inclusive; nozzle '17 by circular columns 28-31 inclusive, and nozzle '19 bycircular columns 32-35 inclusive. These'circular columns define the flow pattern of the liquid into the nozzles and serve to simplify the calculations. The wing tanks, nozzles, and portions of mixing chambers that lie on one side of the ship are identical to the corresponding parts on the other side thereof. In other words, the design is symmetrical about the centerline plane of the ship. The wing tanks, nozzles, and mixing chambers are covered but the confined air does not contribute to the stabilizing (function. As a matter of fact the system is vented to atmosphere at a level above deck E. z I v Each of the

nozzles

14, 16, 17 and 19 is rectangular in cross section. The cross sectional area and the length of run of these nozzles determine the volume per unit of time which the nozzle can pass at the design frequency of the unit. 1

It will be realized that the actual stabilization of the ship against roll is accomplished 'by delay in the flow of the stabilizing water caused by the nozzles. As the ship begins to roll from an equilibrium position, let us say that the ship rolls to starboard as an example, the

the Matsoitia disclosing tendency is for tanks 12 and 13 to discharge their fluid into

tanks

10 and 11. The flow rate in this transfer, however, is limited by nozzles 17 and 14, controlling egress from wing tanks 12 and 13, and nozzles 16 and =19 controlling ingress to

tanks

10 and 11. This flow rate is so calculated that there is a weight of water in the Wing tanks 12 and 13 tending to oppose roll to starboard. By the time the ship has righted itself and is tending to roll to port the liquid will have been transferred to the

tanks

10 and 11 and there will be a weight of water again to oppose roll. Thus, the roll is damped by keeping a body of water sufliciently outboard of the axis of roll so that itjacts through a lever arm to 013 11056101]. It is, of course, to be borne in mind that not only does the weight of excess of water in the wing tanks on one sided the vessel do positive work against roll, but as well the deficiencyof water in the corresponding opposite tanks contributes moment to the same end. This general theory'is not'ditferent from'that disclosed inmy earlier filed applicationybut in the present invention the nozzles are elongated so that water is trapped therein, and thus the water in the nozzles functions as an available weight that entrance to the nozzle which is

tanks

15 and 18 are mixing chambers where the kinetic energy of the discharge is killed.

In my patent application, Serial No. 64,932, filed October 25, 1960, there is shown a safety arrangement for a passive tank stabilizing system suitable for ships of somewhat greater metacentric height than large passenger liners. The purpose of such equipment is to provide for draining the stabilizing system in case the ship begins to heel due to damage so that the torque of the stabilizing system would work with, rather than against, the heel. In the Matsonia, there is provided a dump tank 36 on deck G below the stabilizing system. It extends aft somewhat beyond the wing tanks and 12 inclusive and their connecting nozzles and mixing chambers. Dump tank 36 is connected to tank 12 by a pipe 37 and to tank 13 by a pipe 38.

Similar pipes

39 and 40 on the opposite side of the ship connect

tanks

10 and 11 respectively to the drain tank 36. The

pipes

37, 38, 39 and 40 are provided with valves operable as indicated in my application, Serial No. 64,932, to drain the wing tanks into the tank 36. A swash bulkhead may be provided dump tank 36. This is indicated in FIGURE 4 at 41. Such a plate extends along the centerline plane of the ship and is perforated to break up wave action in the tank 36. The valves in

lines

37, 38, 39 and 40 are suitably operable from an appropriate remote control station of the ship. The pipes 37 to 40 connect to the respective wing tanks close to the outboard edge thereof to make draining complete and quick, even when the ship has substantial heel.

The Matsom'a has a period of about 20 seconds and consequently the transfer of the water in my system from one side of the ship to the other is accomplished in about 10 seconds. This requires considerable velocity and to damp out noise I may employ a swash plate parallel to and near the outboard end walls of the wing tanks. Such plates are so fully perforated as to have negligible effect on water flow rate.

The frequency of oscillation to which my system is tuned is just aboutthe same as the natural frequency of the ship, but transfer is designed to be as nearly as possible 90 out of phase with roll. The frequency of my system is largely controlled by the length of the nozzles while their cross section determines damping. I use four Wing tanks instead of just two in order that the damping of the two may be slightly different. This condition is brought about by putting a slightly different amount of water in the system comprised of tanks 10 and 13 from that comprised of

tanks

11 and 12. This makes the damping effect of the nozzles slightly different so that the system as a whole is very smooth indeed. Needless to say the system of

tanks

11 and 12 and that of tanks 10 and 13 function at the same frequency even though at a somewhat different rate of amplitude decay.

On the Matsonia the nozzles are 3 feet wide at their throats. They are about 10 feet long. The wing tanks 10 and .13 have an average length of 16 feet transversely of the ship, while the

tanks

11 and 12 have an average length of feet measured the same way. The mixing chambers :15 and 18 have lengths of 19% feet and 13% feet respectively, measured transversely of the ship.

What I claim is:

1. A passive stabilization system for ships comprising wing tanks symmetrically disposed on opposite sides of the ship, a mixing chamber therebetween astride the centerline plane of the ship, and an elongated nozzle open at its top and interconnecting each wing tank with the mixing chamber, said nozzles having flared months but being otherwise of uniform cross section throughout their length.

2. A passive stabilization system for ships comprising wing tanks symmetrically disposed on opposite sides of the ship, a mixing chamber therebetween astride the centerline plane of the ship, and an elongated nozzle open at its top and interconnecting each wing tank with the mixing chamber, said nozzles having flared mouths but being otherwise of uniform rectangular cross section throughout their length.

3. A passive stabilizer for a large passenger ship comprising two sub-assemblies both disposed across the ship symmetrically with respect to its centerline plane, and being located immediately adjacent one another lengthwise of the ship, each subassembly including a wing tank on each side of the ship, a centrally disposed mixing chamber therebetween and an elongated nozzle of rectangular cross section open at its top and connecting each wing tank to said mixing chamber, means defining a flared mouth at each end of such nozzle, the cross section of the nozzles being appreciably smaller than that of the wing tanks or mixing chamber, said two sub-assemblies being tuned to essentially the same frequency but being capable of having differing damping of their frequency by reason of containing different amounts of water.

4. A passive stabilizer for a large passenger ship comprising two sub-assemblies both disposed across the ship symmetrically with respect to its centerline plane, and being located immediately adjacent one another lengthwise of the ship each sub-assembly including a wing tank on each side of the ship, a centrally disposed mixing chamber therebetween and an elongated nozzle of rectangular cross section open at its top and connecting each 7 Wing tank to said mixing chamber, columns of circular cross section defining mouths at both ends of each nozzle, the cross section of the nozzles being appreciably smaller than that of the wing tanks or mixing chamber, said two sub-assemblies being tuned to essentially the same frequency but being capable of having differing damping of their frequency by reason of containing different amounts of water.

5. A passive stabilizer for a large passenger ship having a period of about 20 seconds comprising two subassemblies both disposed across the ship symmetrically with respect to its centerline plane and beinglocated immediately adjacent one another lengthwise of the ship in the after position thereof, each sub-assembly including a wing tank on each side of the ship, a centrally disposed mixing chamber therebetween and an elongated nozzle of rectangular cross section open at its top and connecting each wing tank to said mixing chamber, the height of the nozzle being greater than its width, columns of circular cross section defining mouths at both ends of each nozzle, the cross section of the nozzles being appreciably smaller than that of the wing tanks or mixing chamber, but the length thereof being about half of the length of the wing tanks as measured beamwise of the ship, said two sub-assemblies being tuned to the same frequency but being capable of having differing damping of their frequency by reason of containing different amounts of water.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES A.P.C. Application of Hort Ser. No. 132,695, lished May 11, 1943 (now abandoned).

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Claims

1. A PASSIVE STABILIZATION SYSTEM FOR SHIPS COMPRISING WING TANKS SYMMETRICALLY DISPOSED ON OPPOSITE SIDES OF THE SHIP, A MIXING CHAMBER THEREBETWEEN ASTRIDE THE CENTERLINE PLANE OF THE SHIP, AND AN ELONGATED NOZZLE OPEN AT ITS TOP AND INTERCONNECTING EACH WING TANK WITH THE MIXING CHAMBER, SAID NOZZLE HAVING FLARED MOUTHS BUT BEING OTHERWISE OF UNIFORM CROSS SECTION THROUGHOUT THEIR LENGTH.