Ship Model Experiment Research Articles

A slender ship moving at a near-critical speed in a shallow channel

The problem solved concerns a slender ship moving at a near-critical steady speed in a shallow channel, not necessarily in symmetric configuration, involving the special phenomenon of generation of solitary waves. By using the technique of matched asymptotic expansions along with nonlinear shallow-water wave theory, the problem is reduced to a Kadomtsev–Petviashvili equation in the far field, matched with a nearfield solution obtained by an improved slender-body theory, taking the local wave elevation and longitudinal disturbance velocity into account. The ship can be either fixed or free to squat. Besides wave pattern and wave resistance, the hydrodynamic lift force and trim moment are calculated by pressure integration in the fixed-hull case; running sinkage and trim, by condition of hydrodynamic equilibrium in the free-hull case. The numerical procedure for solving the KP equation consists of a finite-difference method, namely, fractional step algorithm with Crank–Nicolson-like schemes in each half step. Calculated results are compared with several published shipmodel experiments and other theoretical predictions; satisfactory agreement is demonstrated.

Speed of Ships in Restricted Navigation Channels

Ship model experiments confirm that orthodox screw-driven craft attain an apparent maximum or barrier speed in navigation channels of restricted width and depth, irrespective of available engine power. This speed is primarily a function of blockage ratio (the relationship between cross-sectional area of the ship to that of the channel). It occurs when conditions alongside become critical at the maximum section; discharge onto the screw is thereby controlled and ship speed becomes limiting. A direct hydraulic jump develops near the stern. A bow-screw arrangement permits acceleration beyond the limiting speed since free flow onto the screw is no longer prevented by critical conditions which now occur downstream. Factors studied during experimentation include ship squat, thrust, power, screw revolutions, water-surface profiles, and water velocities. A two-dimensional theory demonstrates the development of critical conditions around the ship.

Propeller – hull vortex cavitation

A special type of cavitation, here denoted as ‘propeller-hull vortex cavitation’ (hereafter abbreviated PHV cavitation), has been investigated in the cavitation tunnels of The Norwegian Ship Model Experiment Tank. This cavitation appears in the form

On the Mitaka No. 3 Ship Model Experiment Tank of the Ship Research Institute

This paper gives a general description of a new ship model experiment tank, “Mitaka No. 3 Ship Model Experiment Tank”, built at the Ship Research Institute. The principal dimensions of the tank are 150 m×7. 5 m×3. 5 m.The main features of the tank are as follows : 1. towing carriage of box girders convenient to perform various kinds of experiments, not only on ship models but also on ocean structures.2. strong tank wall and special apparatus, which enable the accurate tests in shallow water.3. sub-carriage carrying a small wind tunnel to perform the tests in waves with wind.4. wave maker of plunger type whose vertical position can be varied corresponding to the water level.5. easy control of the towing carriage any one can drive.

On Testing a Ship Model in Transient Water Waves

The ship model experiment in head waves at zero speed were carried out by using transient water waves, and the time histories of wave, heave and pitch amplitude were measured. Then, the experimental results were analysed according to two criteria, that is, both frequency domain and time domain.In consequence of the present investigation, next properties on the ship motion in transient waves were obtained.1) Wave-ship motion system at the same position are one of the linear system. The obtained amplitude ratios and phase lags between waves and ship motions in transient water waves coincide with the measured results in regular water waves. Also, the predicted time histories of ship motions by using the measured wave time histories exactly correspond to the measured ship motion time histories.2) Ship motion-ship motion systems between different points are equal to the wave-wave linear systems, that is, so-called the position shift systems. But, the position shift linear system can not applied in the cases that the concentrating position of transient water waves is existent between the input position and the output position.3) The linear systems of wave height as an input and ship motion at separated position as an output come into existence. But, if the concentrating point of transient water waves exists between the considered points, the linear systems will can not adopt for these points.From the above mentioned results, it can be considered that testing ship models in transient water waves is one of the useful method for the investigation of the ship frequency response function in waves.

On the Mitaka No.2 Ship Model Experiment Tank of the Ship Research Institute

This paper gives a general description of a new ship model experiment tank, “Mitaka No.2 Ship Model Experiment Tank”, built at the Ship Research Institute. The principal dimensions of the tank are 400m × 18m × 8 m with the breadth and depth largest in the world. Because of this huge size of the tank, it took four years to complete all the facilities.In this report are given design considerations and general descriptions of the construction of the tank, which includes the tank itself, the rails, the carriage, the trolley wires, the wave absorbers, the wavemaker, the measuring instruments, the data processor, the building to house facilities, and the workshop and the office.The main features of the experiment tank are as follows ;1. large cross section of the tank.2. deep and shallow trimming tanks with watertight doors.3. four kinds of brake systems for the carriage.4. air-conditioned room on a side part of the carriage.5. accurate speed control of the carriage.6. rigid trolley wires.7. movable wave absorbers at the both sides of the tank wall.8. measuring instruments of digital type with remote control system.9. on-line data processing system.

Speed Stabilizing Controller of Towing Carriage in Ship Model Experiment Tank

Speed Stabilizing Controller of Towing Carriage in Ship Model Experiment Tank

Dr. G. S. Baker, O.B.E

DR. GEOBGE STEPHEN BAKER, who died on August 16, had a world-wide reputation as a man of science and naval architect, who successfully applied the science of hydrodynamics to the design of merchant ships. Dr.Baker was born in 1877 and received his trining (1892–96) at the Royal Dockyard, Porthmouth, as a shipwright apprentice. For his ability he was selected by the Admiralty in 1896 to continue his studies at the R.N.E. College, Keyham, for a year, followed by three years at the R.N. College, Greenwich, where he graduated in 1900 with a first-class professional certificate. He joined the Royal Corps of Naval Constructors, and, after working at Whitehall, he spent five years as Mr. R. E. Froude's assistant at the Admiralty Experiment Works at Haslar, carrying out ship model experiment work. He was then appointed professional secretary to Sir Philip Watts, director of naval construction. In 1910 he was selected by the Royal Society to become the superintendent of its new hydrodynamics laboratory at the National Physical Laboratory, a post which he occupied for thirty-two years. On his retirement at the age of sixty-five in 1942, he remained on the staff until the end of the War, engaged on special research work. From 1945 until his death, he carried out work for the B.S.R.A.