Load Water Line Research Articles

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

A general cargo vessel carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. General cargo vessels are equipped with cargo cranes to facilitate the loading and unloading of cargo. This study aims to determine the relation between speed, resistance, and power using the Holtrop method on vessels with a DWT of 12,335 Tons. The ship was modelled using shipping software, and then validated the results with Holtrop mathematical calculations. Holtrop method for calculating tankers, general cargo, fishing vessels, tugs, passengers, containers, and frigates By using the main dimensions of the ship with Length Over All (LOA) 129.8 m, Length Between Perpendicular (LBP) 110 m, Length On Load Waterline (LWL) 112.75 m, Breadth (B) 18 m. height (H) 9 m, Draft (H) 7.2 m, Speed (V) 12.5 Knots. Tests were carried out on Maxsurf Software by calculating resistance and obtaining a graph that displays the relationship between power and speed and resistance and speed.

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

The ship's resistance affects the selection of the main engine of the ship, especially the bulk carrier ship, which has a significant block coefficient. This study aims to obtain ship resistance with the Holtrop method on bulk carrier ships with a DWT of 30,000 tons. Holtrop method for calculation of tanker, general cargo, fishing vessel, tug, passenger, container, and frigate by using the main dimensions of the ship with Length Between Perpendicular (LPP) 175.27 m, Length on Load Waterline (LWL) 177.95 m, Breadth (B) 24.33 m. height (H) 14.5 m, Draft (T) 10.4 m, Speed (V) 14.5 Knots. Based on computerized results for a speed of 14.5 knots, the ship resistance value is 481.0 KN.

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

A general cargo vessel carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. General cargo vessels are equipped with cargo cranes to facilitate the loading and unloading of cargo. This study aims to determine the relation between speed, resistance, and power using the Holtrop method on vessels with a DWT of 12,335 Tons. The ship was modelled using shipping software, and then validated the results with Holtrop mathematical calculations. Holtrop method for calculating tankers, general cargo, fishing vessels, tugs, passengers, containers, and frigates By using the main dimensions of the ship with Length Over All (LOA) 129.8 m, Length Between Perpendicular (LBP) 110 m, Length On Load Waterline (LWL) 112.75 m, Breadth (B) 18 m. height (H) 9 m, Draft (H) 7.2 m, Speed (V) 12.5 Knots. Tests were carried out on Maxsurf Software by calculating resistance and obtaining a graph that displays the relationship between power and speed and resistance and speed.

Calculation of ice clearing resistance using normal vector of hull form and direct calculation of buoyancy force under the hull

The ice-resistance estimation technique for icebreaking ships had been studied intensively over recent years to meet the needs of designing Arctic vessels. Before testing in the ice model basin, the estimation of a ship’s ice resistance with high reliability is very important to decide the delivered power necessary for level ice operation. The main idea of previous studies came from several empirical formulas, such as Poznyak and Ionov (1981), Enkvist (1972) and Shimansky (1938) methods, in which ice resistance components such as icebreaking, buoyancy and clearing resistances were represented by the integral equations along the Design Load Water Line (DLWL). The current study proposes a few modified methods not only considering the DLWL shape, but also the hull shape under the DLWL. In the proposed methodology, the DLWL shape for icebreaking resistance and the hull shape under the DLWL for buoyancy and clearing resistances can be directly considered in the calculation. Especially, when calculating clearing resistance, the flow pattern of ice particles under the DLWL of ship is assumed to be in accordance with the ice flow observed during ice model testing. This paper also deals with application examples for a few ship designs and its ice model testing programs at the AARC ice model basin. From the comparison of results of the model test and the estimation, the reliability of this estimation technique has been discussed.

Development of estimation system of ice resistance with surface information of hull form

At the initial stage of an ice breaking ship design, a reliable empirical estimation of ice resistance is important to determine the power of the ship. In this study, a prediction method with three dimensional surface information of the ship is presented. The idea is from the existing empirical formula where two-dimensional approach is prevailed. This paper modifies the definition of the hull form with three-dimensional surface information to increase the accuracy. A clearing plane, vector d, the curl between vector p and vector n is adopted. Vector p is the curl between normal vector n at the design load water line and vector i of the ship in the forward direction. A tangential angle is extracted from the vector d and applied to the empirical method. Piece size of broken ice is assumed to be same as the hull form grid and taken in calculation of the clearing force of ice. In the estimation system, a graphical user interface is adopted for easy handling of the relevant data files. Comparison between model test and calculation is provided to validate the system and it is found that the difference is 15% maximum for a hull with a twin-podded system.

左右非対称なデミハルを有する双胴船の性能に関する実験的研究

To capture the ship performances of a catamaran with asymmetric demi-hulls, tank tests were carried out such as resistance test in still water, measurement test of wave height of wash, seakeeping test in regular head waves and captive test for measuring hydrodynamic forces on maneuvering using a scaled model with 2.036m in length. To investigate the effect of clearance of the demi-hulls on the performances, the clearance was changed in the tests as W/B = 2.55, 2.90 and 3.25, where W denotes the breadth overall and B the breadth of the demi-hull. Also, two ship models with different load water line tendencies were used: one is the inside flat and outside round type (IF-type) and the other the outside flat and inside round type (OF-type). The test results obtained are as follows: Residual resistance coefficient of W/B = 2.90 in IF-type is the smallest at the design speed corresponding to Froude number Fn = 0.44 and that of W/B = 2.55 in OF-type is secondary small. In the maximum wave height of the wash, OF-type is almost 30% smaller than IF-type in any demi-hull clearances. In both performances of heave and pitch motions, and added resistance in head waves, OF-type is superior to IF-type near the design speed. Smaller demi-hull clearance and IF-type are better in course keeping performance. The course keeping and turning performances are suitable in any conditions of the catamaran.

A study on improving the course-keeping ability of a pure car carrier in windy conditions

The course-keeping ability of a pure car carrier (PCC) in windy conditions is discussed in this article. Numerical simulations of two PCCs were carried out to compare their course-keeping abilities in wind. The two PCCs had the same hull form but different types of rudder. One PCC was fitted with a semispade rudder (hereinafter, the normal rudder), whereas the other was fitted with a spade-type Schilling rudder (hereinafter, the Schilling rudder). Both PCCs were designed to a new concept for the accommodation structure and hull form above the load water line. In this new design concept, there are no sharp corners in the superstructure so as to reduce wind resistance and improve steering performance. The limits of course keeping for the two PCCs were investigated through simulations. The course-keeping abilities of the two PCCs, each with two different types of autopilot system, were also investigated in wind. To develop the numerical simulation, the hydrodynamic coefficients of the two PCCs were predicted based on the data published for a third PCC having similar principal particulars. The numerical model of the two PCCs was validated by comparing its behavior with the respective full-scale trial results. Wind resistance coefficients were predicted by combining the results of wind tunnel experiments of the object PCCs and a regression model. Numerical simulations under steady wind conditions were also carried out and the results compared with some full-scale experiments to validate the mathematical model of the PCC.

Experimental Study of Wave Pressure on VLCC Running in Short Waves

A free-run experiment of a VLCC model ship was carried out in short regular waves. The wave length and the heading angle were varied in range of 0.2≤λ/L≤1.5 and 0°≤χ≤180° respectively. The ship motion, vertical & lateral bending moment at midship, relative water level and wave pressure were measured. Among them, wave pressure on the side wall near the load water line was the particular interest of this experiment.The first harmonics of the measured data were plotted with calculations of the strip method. We tried two strip methods to compare the accuracy. The first one is so called new strip method “NSM” and the second one is improved NSM we have developed. The solution method for the diffraction problem is improved to satisfy the exact body surface boundary condition. The plots of the measured wave pressure with the calculated value show that the accuracy of NSM is poor when λ/L≤0.5. On the other hand, the accuracy of the improved NSM is still good even when λ/L=0.2.Another difficulty for the estimation of wave pressure amplitude near the load water line comes from the exposure of wall in the air. This phenomenon is essentially non-liner. However, we found a very simple mehod to correct the pressure given by NSM. This method is based on the experimental fact that quasistatic pressuure, which is identical to the static pressure measured from water surface, can be substituted for the wave pressure near the load water line.

Characteristics of Local Stresses and Wave Pressure Working on Hull Side in Seaways

Full-scale measurements of local stresses and wave pressure acting the side of a hull in a seaway were carried out on a VLCC, in an attempt to understand the actual condition of working stresses on longitudinal members and wave pressure acting near the load water line. The findings made from the study are as follows: (1) Results of the full-scale measurements showed that higher order components of wave pressure owing to wave breaking and/or impact were not remarkable. (2) The mean periods of stresses on side longitudinals were shorter than those of deck or bottom longitudinals. This comes from the difference between the response characteristics in regular waves. (3) It was confirmed by comparison with the results of full-scale measurement that the prevalent wave pressure estimation based on strip method explained the short-term characteristics of stress on longitudinals. (4) For the evaluation of local stresses of structural members where various load elements act mutually Discrete Analysis Method (DISAM for short) was found to be effective.

A Study on the Hull Girder Strength of Container Ships with Large Hatch Openings

This paper presents the investigated resuts of numerical simulation pertaining to the hull girder strength of container ships in irregular sea.Using the so-called total system of hull girder strength analysis developed by the authors, the analysis of the long-term prediction of structural response of three container ships is carried out.And the wave-induced stresses in longitudinal strength members, distortion of hatch openings and the torsional deformation of hull girder are studied from the point of view of the long-term prediction.As a result of this simulation, the following conclusions are obtained.(1) In the middle part of ship, the wave-induced normal stress in the upper deck at the side edge of hatch opening is in the stress range of 89.5kg/mm2 and the wave-induced shearing stress in the outer hull at the load water line is below 10kg/mm2 with probability level 10-6.The normal stress of outer hull at the bilge part is in the same level with that of the upper deck.(2) In the fore hold structure, the normal stress of the upper deck is almost in the same level with that of the middle part of ship.Furthermore the torsional deformation of hull girder is considerably large compared with that of the middle part of hull because of the decrease in the torsional rigidities.(3) As to the distortion of hatch openings, the elongation Δl of the diagonal length of them is largest in the hatch of the middle part, but there are small differences in the ratio Δl/l with same probability level.

An Application of Wave Resistance Theory to Hull Form Design

The objective of this paper is to apply linearized wave resistance theory and wave analysis to the hull form design for high speed ships. The paper consists of two parts. One is related to the method of estimation of wave resistance. The other is related to the method of hull form design.We start from the simplification of framelines while we do not vary the sectional area curve, and obtain the calculation formula of wave resistance for simplified hull forms by using Michell's theory. Next we consider a systematic series of parent models, and obtain the estimation formula of wave resistance of the models by comparing between calculation and wave analysis. The hull form of a high speed ship is made by superposing a thin hull form on that of a parent model. Then the amplitude functions of the high speed ship are obtained by superposing the amplitude functions of both hull forms on the basis of the principle of linear superposition.Concerning the method of hull form design, we propose the method to determine sectional area curve and load water line of minimum wave resistance by applying Ritz's method to the estimation formula of wave resistance. Moreover we propose a method to determine principal particulars from a viewpoint of wave resistance.

A Simple Method of Flooding Calculation

Principal part of flooding calculation is divided into three parts. (1) To find the floodable volume so as to make the ship after flooding float at the trimmed water line which crosses the margin line only at one point, and the longitudinal position of its centre of volume. (2) With the given distribution of sectional area below that trimmed water line, to find the floodable length and the position of its middle point. (3) To find the end points of the floodable length curve. In this paper, the following methods are adopted to carry out these calculations.As an extension of the displacement calculation, at several parallel water lines between the load water line and deep water line, the volume above L.W.L. (v), the distance of its centre of volume from midship (λ), the distance of the centre of flotation. from midship, and the corresponding longitudinal metacentric radius (R) are calculated, and the profile between the L.W.L. and margin line with the locus of centre of flotation of even keel water line (I) (scale of depth being taken as ten times that of length), sectional area curve below margin line (II), and the plan area curve of margin line (III) are prepared.(1) Neglecting Leclert's correction, from the centre of flotation of an intermediate even keel water line between m.l. and L.W.L., two tangent lines (or lines through the end points of m.l.) are drawn towards fore part and aft part, and their inclinations α are measured.By virtue of the relationd=V0+v/vR tan α+λ (V0 : vol. below L.W.L.) the longitudinal distance d of the centre of floodable volume v from midship is calculated. (In this formula, d and α are assumed to be positive when referred to the fore part, λ being taken as positive for the centre of volume of layer v allocated after midship.) The draft de of corresponding even keel water line is also noted. With the base of d, curves of v (floodable volume curve) and of de (even keel draft curve) are drawn.(2) As for a certain value of d, the corresponding v and de are read and with (I), through the centre of flotation corresponding to de, a tangent line to margin line is drawn. Now, d being assumed to be the first approximation to the position of the middle point of the floodable length, the sectional area Am below margin line by (II), the height hm between margin line and the tangent by (I), and the breadth bm of the margin line plan area by (III) are taken at the position d, then the sectional area a0 below the trimmed water line at d will be given by a0=Am-bmhm, and the first approximate value of the floodable length 2l will be v/a0. By the same way, the sectional areas ae and am at d±l can be obtained. Assuming the distribution of sectional area below the trimmed water line as a parabola of second order nearly within this range, the exact values of the floodable length LF and the distance of its middle point from a0, section Ej can be given by 2lL and 2le, in which L and e are taken from the diagram of Fig. 4 with the given values of μe=ae/a0 and μm= am/a0.

Award contract construction magnetic survey yacht “Carnegie”

The necessary appropriation having been made by the Trustees of the Carnegie Institution of Washington on December 8th, 1908, the contract for the construction of the magnetic survey yacht Carnegie was awarded on December 9th, as the result of competition, to the Tebo Yacht Basin Company of Brooklyn, New York. The Vice‐President and Manager of this firm has had charge of the building of several well‐known yachts, e.g.; the Meteor (Kaiser Wilhelm's yacht), and the Atlantic, which won the Atlantic cup race of 1906. The vessel is to be completed by July 1, 1909. Mr. Henry J. Gielow of New York City is the naval architect and engineer‐in‐charge; he will be assisted in the work of inspection by Mr. W. J. Peters, formerly in command of the Galilee and to have charge of the Carnegie.The general dimensions of the Carnegie will be: length over all, 155½ feet; length on load water line, 128⅓ feet; beam moulded, 33 feet; draught, 12 feet 7 inches.