Showing papers in "International shipbuilding progress in 1972"
TL;DR: In this article, a new method to calculate the added resistance of a ship in longitudinal waves is discussed, and the particular case of a fast cargo-ship the calculated values are compared with experimental results, and a satisfactory agreement is shown.
Abstract: A new method to calculate the added resistance of a ship in longitudinal waves is discussed. For the particular case of a fast cargo-ship the calculated values are compared with experimental results, and a satisfactory agreement is shown. In addition the experiments with the considered shipform confirm that added resistance varies as the squared wave height for constant speed and wave length.
234 citations
TL;DR: In this paper, the equations for the free undamped vibration of a structure in an ideal incompressible fluid medium and their finite element formulation are briefly reviewed and the relevant matrices (stiffness and loading) for two prismatic fluid elements are given explicitly and some numerical results are presented.
Abstract: The equations for the free undamped vibration of a structure in an ideal incompressible fluid medium and their finite element formulation are briefly reviewed. The relevant matrices (stiffness and loading) for two prismatic fluid elements are given explicitly and some numerical results are presented.
18 citations
TL;DR: In this paper, a special type of cavitation, referred to as "propeller-hull vortex cavitation" (hereinafter abbreviated PHV cavitation), has been investigated in the cavitation tunnels of the Norwegian Ship Model Experiment Tank.
Abstract: A special type of cavitation, here denoted as "propeller-hull vortex cavitation" (hereinafter abbreviated PHV cavitation), has been investigated in the cavitation tunnels of the Norwegian Ship Model Experiment Tank. This cavitation appears in the form of vortices with cavitating cores extending from the propeller to the hull above and ahead of it. There are indications that such cavitation also takes place on certain ships in full scale, and that it may give rise to afterbody noise and vibrations. Systematic observations have been carried out to investigate the effects of afterbody form, tip clearance, propeller loading and cavitation number. Small vertical fins fitted to the hull above the propeller have been found to be very effective in reducing PHV cavitation. Various hypotheses are suggested as possible physical explanations of PHV cavitation.
10 citations
TL;DR: In this article, a review is made of the literature which has been published on the theoretical and experimental plastic behavior of laterally loaded beams and rectangular plates and it is shown that quite reasonable agreement can be achieved between experimental results and the corresponding rigid-plastic predictions provided that both the influence of finite lateral deflections, or geometry changes, and the effect of material strain-rate sensitivity are retained when appropriate.
Abstract: A review is made of the literature which has been published on the theoretical and experimental plastic behavior of laterally loaded beams and rectangular plates. This article focuses attention on these particular structures since they are used extensively in marine vehicles and structural designs in general. It is well known that investigations into the static and dynamic inelastic behavior of structures are simplified considerably when elastic effects can be disregarded. It is shown herein that quite reasonable agreement can be achieved between experimental results and the corresponding rigid-plastic predictions provided that both the influence of finite lateral deflections, or geometry changes, and the effect of material strain-rate sensitivity are retained when appropriate. The results of some recent studies are also reported which indicate that extremely small in-plane displacements at the supports of beams and plates can influence significantly the structural response.
9 citations
TL;DR: In this paper, the results of open-water test results of ducted propeller systems suitable for application on pushboats and tugs are given, and the results with a nozzle specially suited for astern operation are supplied.
Abstract: For the application behind ships two different types of ducted propellers are considered; the ducted propeller where the nozzle accelerates the flow at the propeller and the ducted propeller where the nozzle decelerates the flow at the propeller. The first type of ducted propeller is now extensively used in cases where the ship screw is heavily loaded or where the screw is restricted in diameter. The accelerating nozzle offers a means to increase the efficiency of heavily loaded propellers. The second type of ducted propeller is used to increase the static pressure at the impeller. This nozzle may be used if retardation of propeller cavitation is desired. This paper deals with the first type of nozzle. The open-water test results of ducted propeller systems suitable for application on pushboats and tugs are given. In addition the results with a nozzle specially suited for astern operation are supplied. The effect of the appendages (rudders, struts etc.) on the characteristics of ducted propeller configurations suitable for pushboats and single-screw tugs has been studied. The optimum value of the flanking rudder angle has been determined. Finally, the results of open-water tests with ringpropellers, ringpropellers in nozzles and a multiple nozzle-ringpropeller system are discussed.
7 citations
5 citations
4 citations
TL;DR: In a high speed water tunnel, incipient and desinent cavitation on a series of hemispherical nosed teflon bodies was investigated in this paper, and it was shown that cavitation was probably caused by stream nuclei.
Abstract: In a high speed water tunnel, incipient and desinent cavitation are investigated on a series of hemispherical nosed teflon bodies. The results are compared with those measured previously on a series of stainless steel bodies. The experiments cover a wide range of flow velocities and air contents of water. Large differences, both in cavitation appearance and in desinence and inception values are found between the teflon and stainless steel bodies. While desinent cavitation on the stainless steel bodies was probably caused by stream nuclei, it is shown that cavitation on the teflon bodies is produced by surface nuclei.
4 citations
TL;DR: In this paper, a method is presented for predicting how the steering characteristics of a ship are affected by fitting a fixed nozzles, and it is concluded that propeller, nozzle and rudder should be designed in an integrated way to ensure that an optimum solution is obtained with regard to both propulsive and steering qualities.
Abstract: A method is presented for predicting how the steering characteristics of a ship are affected by fitting a fixed nozzle. The presence of a nozzle upstream appears to have a significant effect on the rudder forces. Full-scale manoeuvring trials carried out with two twin-screw tugs, one with open propellers and the other equipped with nozzles, confirm the predicted trends. It is concluded that propeller, nozzle and rudder should be designed in an integrated way to ensure that an optimum solution is obtained with regard to both propulsive and steering qualities.
3 citations
TL;DR: In this article, a combination of two-phase propulsion, based upon gravity effects, and a ventilated bottom was used for a small cargo ship, and the results obtained are presented in analysed form and discussed.
Abstract: A study is made of a combination of two-phase propulsion, based upon gravity effects, and a ventilated bottom. An explanation is given of propulsion experiments and wake measurements made with a model of a small cargo ship, and the results obtained are presented in analysed form and discussed.
3 citations
TL;DR: In this paper, the results of research into the effect of propeller on ship-propeller interaction and on vibratory forces induced by the propeller are reviewed and a motivation for the need of a large depressurized towing tank is given.
Abstract: In this paper the results of research into the effect of propeller on ship-propeller interaction and on vibratory forces induced by the propeller are reviewed. A motivation for the need of a large depressurized towing tank is given. The areas of research in which an experimental penetration by application of such a 'vacutank' is possible, are discussed.
TL;DR: In this article, an experimental investigation into the motions and powering of a so-called Compact Frigate in waves is described, bearing in mind that not the available power but mainly deck wetness and slamming are governing its sustained sea speed.
Abstract: This report describes an experimental investigation into the motions and powering of a so-called Compact Frigate in waves. Special attention was given to the measurement of the relative motions, with respect to the wave surface along the length of the ship, bearing in mind that not the available power but mainly deck wetness and slamming are governing its sustained sea speed. For that reason, two models having the same main dimensions, weight distribution and underwater cross sections, but different forebody section shapes above water, were tested in regular and irregular head seas, in order to study the effect of flare upon motions and propulsion. In this analysis the deformation of the waves, when traveling along the hull, has been accounted for since the models were also run in restrained condition. The applicability of the linear superposition principle is examined, whereas the model motion measurements are compared with strip theory calculations.
TL;DR: In this article, an investigation has been made to improve the course keeping qualities of an unstable ship by adding a subsidiary automatic control to the manual steering, using results of full scale experiments with a 200,000 DWT tanker and a simulation study.
Abstract: An investigation has been made to improve the course keeping qualities of an unstable ship by adding a subsidiary automatic control to the manual steering. For this, use has been made of results of full scale experiments with a 200,000 DWT tanker and a simulation study. Some instructive results have been obtained.
TL;DR: In this paper, the authors proposed a way to specify the permissible region of instability of a ship from the viewpoint that the ship should be controllable for any human operator without difficulty.
Abstract: The way to specify the permissible region of instability of ships is proposed from the viewpoint that ships should be controllable for any human operator without difficulty. In the case of the steering of the ship (course keeping), where the motions of ships are small, we can approach that problem with a linear equation. The importance of the time constant T, as well as the proportionality coefficient K, is stressed. Assuming a very simple human operator model, which can be followed by any human operator, the permissible region is specified as a combination of T and K.
TL;DR: In this article, the authors discussed the condensation phenomenon in general and the major important factors with regard to condensation risk have been evaluated theoretically as well as practically, and the results from these calculations are compared with measurements that could be performed under normal practical conditions.
Abstract: Condensation may cause severe damage to cargo loaded in containers. The condensation phenomenon is discussed in general. Some major important factors with regard to the condensation risk have been evaluated theoretically as well as practically. A certain transportation situation viz. the transport of tins in cardboard boxes loaded in containers from Australia to Europe v.v. is simulated with the help of an electronic computer. The results from these calculations are compared with measurements that could be performed under normal practical conditions. Recommendations are given concerning the measures that can be taken to avoid or to minimize condensation. Proposals for future work are made.
TL;DR: In this article, a regression analysis is used to express the wake fraction, thrust deduction, hull efficiency and relative rotative efficiency in terms of the varied hull parameters, and the agreement with test results is better than any of the previously suggested expressions.
Abstract: Regression analysis is used to express the wake fraction, thrust deduction, hull efficiency and relative rotative efficiency in terms of the varied hull parameters. The standard errors of the regression equations are small, and the agreement with test results is better than any of the previously suggested expressions. The effect of variation in the propeller diameter is accounted for by correction factors in the form of analytical equations.
TL;DR: In this article, the authors used a series of stainless steel, hemispherical nosed bodies to investigate the parameters which are responsible for cavitation in the case of hydrophilic materials.
Abstract: Ship propellers and other devices which suffer from cavitation, are usually made of hydrophilic materials. The same applies to propeller models made for cavitation experiments in a water tunnel. The results of such experiments are subject to scale effects and often large dispersions occur. To investigate the parameters which are responsible for these effects in the case of hydrophilic materials, incipient and desinent cavitation were determined in a high speed cavitation tunnel, using a series of stainless steel, hemispherical nosed bodies. The experiments covered a wide range of flow velocities and air contents of the water.
TL;DR: In this article, the authors discuss some important aspects of the theory of wave behaviour and wave loads, and give in some detail examples of correlation between extensive calculations and measurements at sea.
Abstract: Behaviour at sea and sea loads are more and more becoming an important consideration in the design of modern ships. Dynamical calculations are often carried out for very large tankers, for LNG carriers, for container-ships, and for a variety of sea-going structures, among which those employed in oil exploitation. All these applications have given an impetus to wave-load calculations. But, engineers are known to attach importance to the validity of their estimates: therefore, along with the development of programmes using the new methods, they have attempted to correlate the results of their calculations to measurement results. The present paper, after having briefly discussed some important aspects of the theory of wave behaviour and wave loads, intends to give in some detail examples of correlation between extensive calculations and measurements at sea.
TL;DR: In this article, two-parameter geometric systems for noses and tails attached to parallel middle bodies in terms of independent polynomials were developed for two-dimensional human bodies.
Abstract: : Two-parameter geometric systems are developed for noses and tails attached to parallel middle bodies in terms of independent polynomials A new parameter is introduced--the rate of change of curvature with arc length at the juncture with the parallel middle body Quadratic polynomials are considered for bodies of revolution and square root polynomials for symmetric two- dimensional bodies Permissible ranges of the two adjustable parameters are obtained for selected geometrical constraints such as the presence of inflection points
TL;DR: In this article, a relation between the dynamic propeller shaft forces and the speed of ship and propeller is derived from two-dimensional considerations, and a factor, defined as the index of unsteadiness, enables the prediction of propeller vibratory force, for conditions different from a test condition.
Abstract: From two-dimensional considerations a relation has been derived between the dynamic propeller shaft forces and the speed of ship and propeller. A factor, defined as the index of unsteadiness, enables the prediction of propeller vibratory force, for conditions different from a test condition. Considerations have been made concerning the level of the vibratory output of multiple propeller arrangements, as compared to regular single propeller arrangements.
TL;DR: In this article, a more detailed analysis of the added resistance of ships in waves is presented, and the practical estimation of the components of the measured added resistance is given, together with a comparison of the calculated and experimental results for a cargo ship.
Abstract: On the basis of a method previously outlined, more detailed analysis of the added resistance of ships in waves is shown. The practical estimation of the components of the added resistance is given. The comparison of the calculated and experimental results for a cargo ship is made also.
TL;DR: The results of an extensive program carried out at the Netherlands Ship Model Basin during the period from 1969 to 1972 are presented in this article, which concluded the investigations carried out in the period between 1963 to 1969 concerning various high-speed propulsion problems.
Abstract: This paper presents the results of an extensive program carried out at the Netherlands Ship Model Basin during the period from 1969 to 1972 This program concluded the investigations carried out in the period from 1963 to 1969 concerning various high-speed propulsion problems Results are given of investigations into friction reduction and cavitation suppression by polymer injection A computer program for the unsteady lifting surface theory for ship screws was extended and some results obtained are given Some results of a study on low-noise propellers are presented Measurements of blade stresses of propellers in a homogeneous flow are given and discussed Towing test results with an air-water ramjet prototype are presented Finally, ship motion studies on a compact frigate are reported