Hull Configurations Research Articles

Time Simulation of Water Shipping for a Ship Advancing in Large Longitudinal Waves

The technique of time-domain numerical simulation for the occurrence of water shipping on board in head waves is presented. The nonlinear effects of the large-amplitude motion are treated. These nonlinear factors include the effect of large wave amplitude, large ship motion, the change of hull configuration below the free surface and the nonlinear resultant wave. Therefore, the variation of the potentials and the hydrodynamic coefficients for a ship at each time step must be carefully treated. While handling the determination of the instantaneous wave surface around the ship hull, the complete incident, diffracted, and radiated wave system is used rather than the incident wave only. The complexity of the ship speed effect on the related terms is also treated at each time step, especially for the radiation problems. An experimental setup is also designed to measure the motion response and the relative motion, and comparisons are made. The results show excellent agreement and the validity of the theory is confirmed. The successful development of the present technique can be extended to analyze the dynamic stability, capsize phenomena, and ship motion in irregular waves

Calculation of the Rise and Pitch of a Three-Dimensional Low-Aspect-Ratio Flat Ship

Using low-aspect-ratio flat ship theory, this paper defines a procedure to determine the position of a hull which is in equilibrium at some "fast" speed in terms of a given hull shape for the same hull at rest. This procedure is then used to find the equilibrium flow past a moving ship, when given the shape of the hull at rest. The method is then extended to find the hull configuration at various speeds based on either the configuration in the static case or at some other equilibrium speed, leading to a calculation of drag versus speed. Some general formulas and some simple examples are given.

A multiple Green's function expression for the hydrodynamic analysis of multi-hull structures

A modified Green's function expression in a multiple function form is developed to evaluate the hydrodynamic coefficients of two-dimensional multi-hull structures floating or fixed in a seaway. Regrettably in conventional singularity methods applied to mono-hulls, twin-hulls, etc., irregular frequencies arise in the numerical analysis. It is shown that when the modified Green's function is used, the numerical analysis is free of irregular frequencies, the numerical accuracy of the results below the lowest irregular frequency is the same as derived from the conventional approach and the physical phenomenon of resonant surface wave interaction is retained in the theory. Results are presented for symmetric and asymmetric twin hull configurations as well as a rectangular mono-hull section heeled to an angle of 15°. A comparison between results evaluated from conventional and modified singularity approaches is also included.

A New Monohull Form Development as Applied to an Offshore Drilling Unit

A new monohull form has been developed specifically in an attempt to combine certain advantages of the semisubmersible and conventional ship shape drilling vessel into a vessel of unique design. The new hull form represents a well-balanced workable design particularly suited to ships where seakeeplng, environmental operability and overall cost-effectiveness are the primary requirements. The basic advantages of the new monohull form when applied to a drillship are as follows:excellent motion characteristics (motions approach those of a comparable semisubmersible);economical advantages in hull fabrication due to the use of straight line framing and developable surfaces;high payload-to-displacement ratio compared with a semisubmersible;large usable deck area compared with a conventional drillship;safety—substantially improved intact stability characteristics, thus incorporating a major advantage of a semisubmersible; anda hull configuration that provides good structural integrity when compared with a semisubmersible.

Design of 40-MW Grazing and Moored OTEC Pilot/Demonstration Plants

Designs are presented and discussed for a plantship that cruises the tropical oceans, where the electrical energy generated by ocean thermal energy conversion (OTEC) is used to produce ammonia, replacing natural gas used in ammonia manufacture; and for a moored OTEC plant from which the electrical power is transmitted by undersea cable to an offshore island (Hawaii, Puerto Rico). Both designs use the same OTEC electric generating plants, seawater pumping systems, cold water pipe, and barge-type hull configuration developed from and similar to earlier designs. The OTEC power generating plants and the alternative usage equipment and plant processes are described, together with the integration and operational aspects of an ocean platform installation. The estimated performance, at the annual average temperature difference available, is 33.8 MW delivered onshore at Puerto Rico and 42.5 MW to product process on the cruising plantship. Acquisition and deployment costs are estimated at $171 million for the moored plant and $144 million for the cruising plantship in 1980 dollars. These costs assume all heat exchangers are the folded-tube design and do not include general contractor profit or contingencies.

A GUIDE TO GENERICSEAKEEPING PERFORMANCE ASSESSMENT

ABSTRACTThe generic interrelationships between seakeeping performance, hull configuration, and ship displacement are explored. Results are presented graphically as envelopes of Attainable Seakeeping Performance versus Displacement. The scope of the envelope at a given displacement indicates the performance variability attainable through configuration changes. These performance envelopes admit evaluation of seakeeping at the earliest stages of the ship design process. They can be used to establish the performance attainable at a given displacement, the displacement required to attain a given performance level, or the feasibility of simultaneous constraints on performance and displacement.

Predicting Hydrodynamic Behavior of Small-Waterplane-Area Twin-Hull Ships

Existing naval and commercial small-waterplane-area, twin-hull (SWATH) vessels are described along with the reasons for choosing this type of hull configuration. The effects of changes in hull form and proportions on smooth water resistance and motions in rough water are examined. Analytical and experimental techniques presently available for use in the design process are discussed. Simple relationships for use in predicting resistance and seakeeping behavior in early stages of design are presented.

Motion and Load Prediction of Floating Pipelaying Equipment

In predicting the motions and loads of floating pipelaying equipment - varying from conventional barges to large, highly sophisticated semisubmersibles - several mathematical methods and model experimental techniques are available. This paper reviews the various mathematical methods and correlates the results with model test and prototype data. Introduction The concept of a floating barge being a stable floating unit for carrying pipelaying equipment offshore was introduced in 1956. In 1978, the first offshore pipelaying barge, the L.E. Minor, was operated. The pipeline was lowered from the barge to the seafloor using long submerged floating units. By controlling the buoyancy of these units, the required sloping launchway was obtained. Tension was applied only to prevent slipping of the pipeline. The length of such stingers was two to three times the water depth. Stingers up to about 1,000 ft long with a weight up to 250 tons were used. In deeper water and less-sheltered areas, however, stingers of such length and weight became a real problem, especially because of the very large moments generated about the attachment point to the barge. By the introduction of the curves stinger in combination with large axial tensions applied to the pipeline on the barge, the sagbend could be limited so that laying in greater water depth became possible. Allowing a stress level of about 80% of the yielded stress during the laying operations resulted in considerably shorter stingers. Hence, the very large moments about the attachment point to the barge were reduced, which made work in rougher sea conditions possible. Generally, however, the laying techniques themselves hardly changed. The hull configuration of the unit supporting the pipelaying equipment has varied considerably during the last 10 years. Ship-shaped vessels, small semisubmersibles, and large semisubmersibles with sophisticated pipelaying-controlling systems were developed and taken into operation, in addition to conventional flat-bottom barges. The choice of the type of construction is determined mainly by the following parameters1–3:operational area (worldwide or some specific area - e.g., North Sea, Gulf of Mexico),water depth,size of pipelines (storage capacity, deck area),seabed condition,sea surface condition (workable days, survival capability, stability), andinvestment. Due to high development and operating costs of pipelaying barges, it is important to consider the various possibilities in early stage. Sea surface conditions and, thus, the hydrodynamic aspects of the various concepts play an important role in the selection of the final concept. The waves, wind, and current acting on the floating pipelaying structure determine mainly whether motions and forces become too large so that the laying activities have to be stopped. The rougher the sea conditions in which it is possible to work, the more time will be available for productive pipelaying in a given season.

The performance potential of semisubmerged ships

As a contribution to the current debates about the potential of semisubmerged ships (cu S), this paper presents estimates of the lowest possible resistance/displacement ratio. That is, the resitance of the submerged form alone is calculated, without reference to the additional components due to necessary struts, rudders, and other appendages. It is suggested that the Priest hull configuration is better than the more recent SWATH, because of its reduced wetted area, and that, like hydrofoil and SES, cu S should probably rise up is the water for high-speed flight. This then removes the serious constraint that the struts must provide adequate hydrostatic stability, since this stability can now be provided by the upper hull, which is in contact with the water at low speeds. At higher speeds, roll stability can be provided by the submerged foils which in any case seem to be required for adequate control.

STRUCTURAL INTEGRITY CRITERIA FOR NEW HULL MATERIALS

ABSTRACTApplication of new advanced structural hull materials and/or novel ship hull configurations can have serious disruptive effects on the building ways and in service if proper attention to details is not applied in the early stages of development and design. This brief paper addresses rudimentary considerations to ensure structural integrity of the finished product. Application of structural integrity in the areas of material selection, flaw growth, design requirements, fabrication and maintenance, and the supporting technology development work is briefly discussed.

Gulf-Stream-Based, Ocean-Thermal Power Plants

This paper presents the results of an ongoing analytical study at the Univ. of Mass, for the design of major components and a total power system for Gulf-Stream-based ocean-thermal power of 400 Megawatts electrical net power output. On the basis of these studies, the ultimate power potential of a 15 mile wide by 550 miles long length of the Gulf-Stream extending from south of Miami, Fla. to Charleston, S.C. is estimated to be approximately 2 trillion kilowatt hours per year which could be transmitted to shore by undersea cables. Critical subsystems and components (such as heat exchangers, ocean-based hulls, and cold water inlet pipe) are identified, and the technical basis for their configuration and design is discussed. 90/10 copper-nickel alloy plate-fin heat exchangers, with propane flowing upward (evaporators) or downward (condensers) through small passages in the plates and sea water flowing horizontally between the plates, have been selected. The latest power system (Mark II) is based on a submerged, twin catamaran concrete hull configuration with hulls approximately 80 ft in diameter by 800 ft long. The evaporators are staggered serially in height in 6 tiers placed above the twin hulls which contain the condensers, turbines, pump, and other power cycle components. A cold-water inlet pipe of elliptical cross section (1500 ft long and with a hydraulic diameter of 87 ft) is hinged between the hulls with a gun-buckler type joint. Technical problems facing the deployment of such plants are summarized, and the latest cost estimates predict busbar power costs of approximately 15 mills per kilowatt hour.

Designer's dilemma

The authors' consider a designers dilemma; how does a naval architect approach the design of an inherently unsound ship type; the ro/ro monohull, in order to satisfy commercial, technical, legal and ethical consideration? This paper reviews a number of areas of ro-ro design which influence safety, including hull form, sub-division, general arrangement, devices and appendages. Economic performance and safety of alternative ro-ro hull configurations are considered. The weaknesses of SOLAS 90 are analysed and alternative approaches to ro-ro safety assessment are considered which might be applied in conjunction with SOLAS 90 in the short term. Finally a better approach is suggested for designers attempting to comply with current legislation in vessels which must work within existing constraints set by port facilities and commercial pressures.

Intersecting Titanium Spheres for Deep Submersibles

An evaluation of a bispherical pressure hull configuration and the investigation of the use of ceramics in pressure vessels is presented. A one-fourteenth scale model made of titanium 6Al-4V alloy was designed for an operating depth of 20,000 ft and for a collapse depth of 30,000 ft. Also incorporated into the design was the replacement of the integral titanium reinforcing ring by a high-strength, light-weight ceramic (A1 2 O 3 ) ring resulting in a 10% increase in payload. A structural model test program was initiated to experimentally evaluate the design of the intersecting sphere configuration with and without the ceramic reinforcing ring. Experimental results were in good agreement with analytical predictions and serve to verify the validity of the analytical techniques employed.

Design Aspects of Stern-Mounted Propellers for Deep-Submergence Vehicles

This paper presents the results of model tests carried out on two alternate hull configurations for a proposed deep-submersible vessel. The experiments consisted of resistance tests, propeller tests, self-propelled tests to derive the propeller-hull interaction effects for a range of vehicle drags (corresponding to different amounts of externally-mounted, resistance-increasing equipment), and Pitot-tube wake surveys carried out in way of the propeller plane. The two configurations differed in respect to the relative stubbiness of their afterbodies, both having a single relatively large diameter, stern-mounted propeller. The data are analyzed and comparisons are made with alternate propulsion configurations. The influence of propeller diameter on power and rpm is studied. A discussion of relevant data available in other sources is presented. A recommendation is made to carry out full-scale resistance tests of deep-submergence vehicles by the method of free deceleration.

Application Of A Panel Method To The Hydro Dynamic Analysis Of Advanced Vehicles

The present paper illustrates the potentialities of a Rankine source panel method to the hydrodynamic analysis of advanced vehicles. The framework of the mathematical model was the linear steady Rankine source formulation for the mono hulls wave resistance characterisation presented in ref 1. The theoretical formulation of the linearized boundary value problem for the steady wave perturbation which takes into account also the perturbation due to an air supported catamaran (SES) is provided. Extension of the monohull methodology has been carried out to account for twin hull configurations and air cushion catamarans. The former problem was more troublesome from a computational point of view as it involved a redefinition of the free surface grid and of the finite difference operator in the transverse direction. The latter problem was accomplished by adding some terms into the free surface boundary condition. All the hydrodynamic computation is evaluated for given trim and draft conditions assuming a given fixed geometry. Equilibrium condition can be obtained by the user by iteratively running the program. Applications are herein presented for simple configurations in order to validate the methodology.

Drilling in 1,300 Feet of WaterSanta Barbara Channel, California

Available technology and equipment have proven adequate for carrying out successful floating drilling operations in water depths to 1,300 feet on federal leases in the Santa Barbara Channel of California. System elements directly affected by water depth have performed satisfactorily with only a few minor design modifications. Introduction During the 12-month period following the Feb. 6, 1968, federal lease sale in the Santa Barbara Channel, Humble drilled 10 wells with floating rigs, three of which are in water depths of 900 to 1,300 ft. The adequacy of advance planning has been demonstrated by the fact that few problems have occurred directly related to water depth. The first of the deep-water wells was spudded in 994 ft of water on Aug. 5, 1968 (Fig. 1). This rig (WODECO IV) bas now completed the drilling of a well in 1,300 ft of water. The first deep-water well for the second rig (Blue Water II) was spudded in 941 ft of water on Dec. 3, 1968. (See Fig. 2)It is our purpose here to present information on the location and environment of the deep-water drilling program; the criteria governing selection of the jigs used; details of the systems used, including design considerations and methods; and operating procedures and results. The Santa Barbara Channel Winds, Waves and Currents The Santa Barbara Channel is an area of the Pacific Ocean that is bounded on the north by the portion of the California coastline extending from Point Conception on the west to Ventura on the east and is bounded on the south by the Channel Islands of San Miguel, Santa Cruz and Anacapa. Industry's previous experience with floating drilling in the Channel had shown the environment to be relatively mild. Oceanographic and meteorological references provided the best available data on winds, waves and currents for guidance in selecting and designing equipment and in formulating operating practices. (Fig. 1 shows sites in the area covered by specific reports.) Historical data indicated that the probable yearly maximum conditions in the central Santa Barbara Channel would not exceed 5-minute average winds of 65 knots from the west and northwest or from the east and southeast; significant wave heights of 16 ft with a period of 13 seconds (Maximum waves associated with this sea state would probably be approximately 30 feet.); surface or near-surface currents of 2.4 knots parallel to the California coastline. The data showed parallel to the California coastline. The data showed generally that these conditions would occur for only a very small percentage of the time in winter months in the main part of the Channel east of Point Conception. Near the west end of the Channel, a yearly maximum significant wave height of 18 feet might occur with somewhat greater frequency. Criteria for Rig Selection On the basis of the water depths for the leases offered, the rig selection criteria emphasized deep water operations and the economics of timing. Factors considered for selecting from the available vessels are as follows. Sufficient drilling-depth capability of the rig. Strength and stability of basic hull configuration. JPT P. 27

Stability of a Submerged Stiffened Cylinder

The possibility of local panel buckling in the hull is investigated. The configuration of a section of the hull is idealized to be a thin cylindrical shell with discrete, internal, circumferential and longitudinal stiffeners. The loading is idealized to be composed to two parts which are (1) A uniform external pressure applied to the hull and to the bulkheads, and (2) an axial load which is applied through the bulkheads. An analytical procedure is presented which predicts the pressure necessary for buckling in the case of a specified axial load. Results of the analytical procedure are given for five possible hull configurations as well as for a case whose experimental buckling pressure had been reported earlier. Consequently the results of this study can be used to help evaluate various hull designs. Results deduced by the procedure presented here have application to the design of caissons, tunnels and possibly large pipelines.

THE BUREAU OF NAVAL WEAPONS HYDROFOIL SEAPLANE

Naval Engineers JournalVolume 75, Issue 2 p. 449-452 THE BUREAU OF NAVAL WEAPONS HYDROFOIL SEAPLANE EUGENE HANDLER, EUGENE HANDLER The author is the Bureau of Naval Weapons aircraft hydrodynamics engineer. He is responsible for the Bureau's support of Navy water-based aircraft programs and the associated research studies and full scale evaluations of hydro-skis, hydrofoil and hull configurations, amphibious helicopters and air-towed water-borne vehicles. In 1942, Mr. Handler received a Rockefeller Foundation Fellowship to the Graduate School of Applied Mathematics of Brown University. In 1943, he was assigned by the National Defense Research Committee to the David Taylor Model Basin where he participated in research concerning the underwater trajectories of air-dropped depth charges. Following service in the Eighth and Far Eastern Air Forces, he returned to Brown, and received a Masters' degree in Engineering in 1949. Mr. Handler was employed at the Glenn L. Martin Company for several years, primarily with towing tank tests of patrol seaplanes and the P6M mine layer. He left the Martin Company for the Bureau of Aeronautics in 1954.Search for more papers by this author EUGENE HANDLER, EUGENE HANDLER The author is the Bureau of Naval Weapons aircraft hydrodynamics engineer. He is responsible for the Bureau's support of Navy water-based aircraft programs and the associated research studies and full scale evaluations of hydro-skis, hydrofoil and hull configurations, amphibious helicopters and air-towed water-borne vehicles. In 1942, Mr. Handler received a Rockefeller Foundation Fellowship to the Graduate School of Applied Mathematics of Brown University. In 1943, he was assigned by the National Defense Research Committee to the David Taylor Model Basin where he participated in research concerning the underwater trajectories of air-dropped depth charges. Following service in the Eighth and Far Eastern Air Forces, he returned to Brown, and received a Masters' degree in Engineering in 1949. Mr. Handler was employed at the Glenn L. Martin Company for several years, primarily with towing tank tests of patrol seaplanes and the P6M mine layer. He left the Martin Company for the Bureau of Aeronautics in 1954.Search for more papers by this author First published: May 1963 https://doi.org/10.1111/j.1559-3584.1963.tb04886.xCitations: 1 AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume75, Issue2May 1963Pages 449-452 RelatedInformation