Journal of Zosen Kiokai 

About: Journal of Zosen Kiokai is an academic journal. The journal publishes majorly in the area(s): Hull & Propeller. It has an ISSN identifier of 1884-2062. Over the lifetime, 549 publications have been published receiving 1429 citations.

On the Steering Qualities of Ships

Abstract: While there have been a number of scholarly studies on the steering of ships, the concerned design practice remains quite experiential.On the other hand, the modern devlopments of communication and control engineering offer us a successful method for the analysis and synthesis of the control of various physical systems.Then, the authors have applied the method to the problem of steering of ships, expecting that it supplies a more rational and practical basis of design works.The present paper is the first report of the work, and consists of three parts a glance of steering problems in the aspect of control engineering, the representation of steering characters of a ship with the transfer function, and the determination of the transfer function from experiments with a free self-propelled model or an actual ship.

On Steering Qualities of Ships (2)

Abstract: This paper follows the preceding paper of the authors in 1956. Now it may be concluded that ; (1) Steering quality of a ship may be described by a transfer function of the form K (1+T3p) / (1+T1p) (1+T2p) or a set of the steering quality indices K, T1, T2 and T3. These indices are functions of hull form, rudder size and other particulars of a ship. Analytically, they are composed of coefficients of governing equations of motion.(2) In a more practical sense, steering motions of ships are described substantially by a first-order equation of motion T dθ/dt+θ=Kδ. Accordingly steering quality may be described in brief by two fundamental indices K and T.(3) Use of the transient response test and frequency response test of a free self-propelled model is an effective means of providing a full description of steering quality in terms of K, T1, T2 and T3, through a procedure not so lengthy as the usual approach of resistance derivatives.(4) Kempf's zig-zag test followed by an analysis employing the first-order equation of motion provides a figure of merit for steering qualities of actual ships in terms of K and T. The zig-zag test would bring out many things about steering quality if it were carried out for many ships.(5) Refering the values of K and T for a number of actual ships, it may be said that (a) improvement of turning ability (increase of K) brings necessarily some reduction of quick-responsibility and stability in steering (increase of T), if the relative rudder size remains constant, (b) rudder size, cut-up of dead-wood and other similar arrangement have fair effects for steering quality, while main hull form has much smaller effects for it.(6) It may be expected that the present expression of steering quality would provide a reasonable basis for design work relating to steering and turning. In this connection, consideration of a feed-back system composed of a ship, a steering gear and a helmsman or anautopilot may be an important aid.

On the Damping Force and added Mass of Ships Heaving and Pitching

Abstract: When cylinders of Lewis Form sections heave and pitch on the free surface, their damping force and the added mass were exactly calculated by Ursell's Method. And many figures in this report show the results of the calculation. Then the reporter calculated, applying the results of the above-mentioned calculation and by Strip Method, the damping force and the added mass of the two ships, which were respectively put to test by Golovato and Gerritsuma. The added mass and the added moment of inertia which the reporter gained by Strip Method showed good coincidence with the results of Golovato's and Gerritsuma's experiments. To get better estimation on the damping force by Strip Method, it is necessary to calculate more closely the three dimensional effect, non-linear effect, etc. As to the added mass the three dimensional correction could be negligible except for small ξ1*.

Experimental Researches on Rudder Performance. (2)

Abstract: The present paper relates to experimental researches on rudder performance utilizing a free running, self-propelled model.Hardover to hardover steering tests have been carried out on four different balance ratios including the optimum one estimated by turning tests, and it is known that the balance ratio must be selected so as to prevent the abnormally large positive torque which may occur when the rudder is steered from port to starboard.An interpretation for the complicated rudder performance during the turning tests have been tried using the results of behind tests and free model tests. As the results, the resonable values for normal force coefficients have been provided through considering the change of slip ratio of propeller and drift angle of ship, but it remains some problems to be investigated for the center of pressure.

On the Measurement of Added Mass and Added Moment of Inertia for ship Motions

Abstract: A forced oscillation method same as was used in the case of pitching was employed. The effects : of ship forms upon additional mass and damping force are discussed about the values corresponding to the ship's natural frequency.It was found that the ratio additional mass to ship's own mass increases when Cb and B/L increases, that damping coefficent decreases when Cb, increases and increases when B/L increases. Charts of added mass coefficent and damping coefficent same as for pitching motion are also proposed in this paper.