bluuebunny/crossref_metadata_2025 huggingface dataset:
Formulation of Multicriterion Design Optimization Problems for Solution With Scalar Numerical Optimization Methods
Authors: Parsons Michael G. , Scott Randall L.
Published: January 2021

Most marine design problems involve multiple conflicting criteria, objectives, or goals. The most common definition of the multicriterion optimum is the Pareto optimum, which usually results in a set of solutions. Design teams, however, need to arrive at a single answer that provides an acceptable compromise solution within the Pareto set. Methods have been developed to solve multicriterion optimization problems using a number of related definitions of the compromise solution or "optimum" in the presence of multiple conflicting criteria. The most common of these definitions are reviewed and their solutions are formulated in a consistent form utilizing a preference function that will allow their solution using conventional scalar criterion numerical optimization methods. This approach permits the use and comparison of the various definitions of the multicriterion "optimum" with modest additional computation. The design team can use these results to guide its selection of the solution that best reflects their design intent in a particular case. A sixparameter, three-criterion, 14-to 16-constraint conceptual marine design optimization example adapted from the literature is presented to illustrate the use of this approach. The results for the various definitions of the multicriterion optimum for Panamax and post-Panamax bulk carriers are presented for comparison.
Experimental Investigation of the Propeller Wake at Different Loading Conditions by Particle Image Velocimetry
Authors: Di Felice F.
Published: January 2021

An experimental investigation of the propeller wake in a cavitation tunnel has been performed using particle image velocimetry (PIV). A PIV image analysis algorithm implementing iterative window offset and stretching has been adopted. The main characteristics of the propeller wake at different loading conditions have been pointed out by using phase sampling techniques. Longitudinal evolution of the blade viscous wake, developing from the blade surface boundary layers, of the trailing vortex sheets, due to the radial gradient of the bound circulation, is discussed up to 1 diameter downstream. In the near field the effects of turbulent diffusion and viscous dissipation, which cause a rapid space broadening of the velocity gradients in the trailing edge wake, are also examined. In the far wake the development of the slipstream instability and the breakdown of the hub and tip vortices are outlined.
Ultimate Compressive Strength of Imperfect Unstiffened Plates: Simple Design Equations
Authors: Masaoka Koji , Mansour Alaa
Published: January 2021

A simple design equation for predicting the ultimate compressive strength of unstiffened plates with misalignment, initial deflection, and welding residual stresses is developed in this study. A nonlinear finite element method is used to investigate the ultimate strength of the imperfect plate. The method incorporates both geometric and material nonlinearity. Buckling and plasticity behavior of the plate can be expressed using this finite element system. The results from the finite element method and an analytical method using large deflection theory together with rigid-plastic theory are compared. It was found that the analytical method using large deflection and rigid-plastic theory is not always accurate. Reduction factors of the ultimate strength due to welding residual stresses and initial deflection are generated from the results of the nonlinear finite element method. A new equation for ultimate strength of imperfect plates was developed using these reduction factors. The accuracy of the proposed new equation is confirmed by comparing it with the finite element results.
Added Resistance by Means of Time-Domain Models in Seakeeping
Authors: Hermans A.J.
Published: January 2021

In many applications in seakeeping the added resistance plays an important role. It is observed that many of the existing methods underestimate the added resistance at low wave frequencies. This may be due to the way the potential is split up. It is shown that with the help of the steady wave potential obtained by RAPID, a linearization around the obtained steady free surface is possible and that the results obtained with a time-domain approach fit very well with the experimental results for a liquid natural gas (LNG) carrier obtained at MARIN. Also an asymptotic theory is presented that is able to predict the added resistance at low forward speed with rather simple means. In this case the problem is linearized with respect to the double body potential. Some results are shown for a circular cylinder.
An Inverse Design Approach in Determining the Optimal Shape of Bulbous Bow With Experimental Verification
Authors: Chen Po-Fan , Huang Cheng-Hung , Fang Ming-Chung , Chou Jar-Hung
Published: January 2021

An inverse design algorithm in determining the optimal shape of the bulbous bow was developed by utilizing the Levenberg-Marquardt method (LMM) and B-spline surface control technique and basing it on a given design target, such as the desired wave height or wave resistance coefficient. A Wu-Chiang ferry used for domestic traffic in Taiwan was selected as the example ship for this study. Two different design objects, the bow wave profile and wave-making resistance, were considered the target functions. To verify the inverse design algorithm, towing tests were performed for two ship models: the original hull and the hull with optimal bulbous bow. Test results showed that the optimal bulbous bow designed by inverse algorithm improves the ship performance as expected.
Active Motion Control of High-Speed Hydrofoil Vessels by State-Space Methods
Authors: Hatzakis Iason , Sclavounos Paul D.
Published: January 2021

Hydrofoil ships cruising at high speeds often operate in rough weather conditions and hence experience uncomfortable or even unsafe motions without the use of some form of motion control. The research described here concerns an active motion control mechanism for high-speed hydrofoil vessels, aiming at the significant reduction of the vessel motions in regular and random waves. The seakeeping equations of motion are cast into a linear state-space form leading to a linear-quadratic optimal controller shown to attenuate the vessel motion responses significantly. The deterministic control laws designed in the present study are found to perform satisfactorily both in monochromatic and random waves for high-speed vessels supported by hydrofoils and buoyancy.
Green Function of Steady Motion in Finite Water Depth
Authors: Yang Qinzheng , Faltinsen Odd M. , Zhao Rong
Published: January 2021

The Green function associated with a steady translating source on a straight horizontal course in water with finite constant depth and infinite horizontal extent satisfying the classical free surface condition is studied by decomposing it into three parts: an array of Rankine singularities A, local disturbance D, and downstream wave part S. Each of the three parts is studied by several methods. This is used to verify the numerical scheme and find the most time-efficient procedure. The method of repeated averaging of partial sums for oscillating series is efficiently used to evaluate the infinite sum of Rankine singularities and the downstream wave part. The local disturbance needed in vertical force and pitch moment calculations is most demanding. The Green function is used in combination with thin ship theory to calculate wave resistance, vertical force, pitch moment, and far-field wash for a Wigley hull. The results are compared with Tuck's (1966) slender body theory for shallow water and experimental and theoretical results of wave resistance by Everest and Hogben (1970). The agreement is satisfactory. A shallow water wave resistance ratio r expressing the ratio between wave resistance in finite depth and infinite depth is introduced as an indirect way to minimize wash. It is demonstrated that a large influence of critical depth Froude number requires the ratio between fluid depth and ship length to be small.
Effect of Damping on Parametrically Excited Torsional Vibrations of Reciprocating Engines Including Gas Forces
Authors: Pasricha M. S.
Published: January 2021

In recent years, several cases of secondary resonance have been found in torsional vibrations of crankshaft systems. In some reciprocating large marine diesel engine systems, these effects have been a contributing factor of catastrophic failures. In these instances, design based on invariable inertia characteristics of the systems and using constant damping could not project the existence of adverse situations that led to excessively large motions. Most of the mathematical models considered thus far either give limited information on the effects of damping or restrict the analysis to an undamped variable inertia system with gas forces to avoid complexities. As a result, these models do not highlight all the consequences of such motion. This paper presents the equation of motion with key nondimensional parameters to include both damping and external excitations in order to predict the complete response of an equivalent single-cylinder engine system. Additionally, the nondimensional mathematical model presented in this paper allows development of design charts and brings the analysis closer to becoming an effective design tool. This model extends the previous analytical model by the author (2001) to include the effects of damping and gas forces acting on the system and captures many of the important concepts of time-dependent inertia systems. The complex waveform responses are examined within the range of engine speeds at which inexplicable crankshaft failures are known to have occurred. The investigations are conducted to study the interaction of secondary resonance effects with harmonic excitations for variation in damping and inertia ratios. These studies show that the observed effect is a natural physical phenomenon arising from the variable inertia characteristics of the system, and under certain circumstances it can have a serious impact on torsional vibration. The conclusions reached in this paper differ from those of Draminsky (1961) and Hesterman and Stone (1994). Comments on these differences are also included.
First-Failure–Based Reliability Assessment and Sensitivity Analysis of a Naval Vessel Under Hogging
Authors: Lua James , Hess Paul E.
Published: January 2021

PULSTR, a probabilistic version of ULTSTR (ULTimate STRength), has been developed to perform probabilistic analysis and reliability-based design of a hull-girder under longitudinal bending. The ULTSTR deterministic solver has been integrated with a probabilistic integrator based on either the Monte Carlo simulation (MCS) or the first-order reliability method (FORM). In order to explore the remaining safety margin after the first-failure and the dominant failure mode and failure location, the hull reliability model is formulated based on its initial failure moment. A hybrid (MCS/ FORM) solution approach is employed to assess the hull reliability associated with the first failure, such as panel/stiffener buckling and stiffener tripping in the reduced random variable space. An adaptive response surface module is developed and used to extract the first-order reliability sensitivity in the full random variable space based on the MCS results of the hybrid approach. The dominant failure mode, remaining safety margin after the first failure, and the use of sensitivity factors for making design decisions are illustrated via an example application of a Navy combatant hull girder under hogging.
Analytical Prediction of Capsizing Probability of a Ship in Beam Wind and Waves
Authors: Paroka Daeng , Ohkura Yuuichi , Umeda Naoya
Published: January 2021

This paper presents a set of formulae to evaluate capsizing probability of a ship in both beam wind and waves based on a piece-wise linear approximation of roll restoring moment with and without simplifications as an extension of the work by Belenky (1993). The new simplified formula is also proposed on the basis of sto-chastic properties of roll motion near the angle of vanishing stability. These formulae are applied to a car carrier having a large windage area. As a result, it was pointed out that Belenky's simplified method could overestimate capsizing probability if the apparent roll angle model is used. The capsizing probability in both wind and waves is definitely larger than that in waves on their own. It was remarked that steeper waves or narrower wave spectrum do not always provide larger capsizing probability.
Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer
Authors: Lasher William C. , Richards Peter J.
Published: January 2021

Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.
A Study of Water Surface Deformation Due to Tip Vortices Wing-in-Ground Effect
Authors: Barber Tracie J.
Published: January 2021

The accurate prediction of ground effect aerodynamics is an important aspect of wing-in-ground (WIG) effect vehicle design. When WIG vehicles operate over water, the deformation of the nonrigid surface beneath the body may affect the aerodynamic performance of the craft. The likely surface deformation has been considered from a theoretical and numerical position. Both two-dimensional and three-dimensional cases have been considered, and results show that any deformation occurring on the water surface is likely to be caused by the wing tip vortices rather than an increased pressure distribution beneath the wing.
Unsteady Effects During Resistance Tests on a Ship Model in a Towing Tank
Authors: Doctors Lawrence J. , Day Alexander H. , Clelland David
Published: January 2021

It is known that there are oscillations in the wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model. In this work, the unsteady thin-ship resistance theory has been applied to this case. The results have been compared with experiment data obtained using a towing carriage the velocity history of which can be programmed. It is demonstrated here that generally excellent correlation exists between the theory and the experiments. In particular, one can predict the influence of Froude number, rate of acceleration, and type of smoothing of the acceleration on the characteristics of the oscillations. These characteristics include the amplitude, rate of decay, frequency, and phasing of the oscillations in the curve of wave resistance versus time.
Parametric Identification of Ship Maneuvering Models by Using Support Vector Machines
Authors: Luo W. L. , Zou Z. J.
Published: January 2021

System identification combined with free-running model tests or full-scale trials is one of the effective methods to determine the hydrodynamic coefficients in the mathematical models of ship maneuvering motion. By analyzing the available data, including rudder angle, surge speed, sway speed, yaw rate, and so forth, a method based on support vector machines (SVM) to estimate the hydrodynamic coefficients is proposed for conventional surface ships. The coefficients are contained in the expansion of the inner product of a linear kernel function. Predictions of maneuvering motion are conducted by using the parameters identified. The results of identification and simulation demonstrate the validity of the identification algorithm proposed. The simultaneous drift and multicollinearity are diminished by introducing an additional ramp signal to the training samples. Comparison between the simulated and predicted motion variables from different maneuvers shows good predictive ability of the trained SVM.
Analysis of Hydroelasticity of Floating Shiplike Structure in Time Domain Using a Fully Coupled Hybrid BEM-FEM
Authors: Kim Yooil , Kim Kyong-Hwan , Kim Yonghwan
Published: January 2021

A fully coupled time-domain ship hydroelasticity problem focusing on a springing phenomenon is considered in this study using a hybrid boundary element method (BEM) finite element method (FEM) scheme. The fluid domain surrounding a flexible vessel is handled with a boundary element method adopting a higher-order B-spline Rankine panel method. The structural domain is modeled by a finite element method relying on the one-dimensional beam element, which is able to capture the coupling effect between torsion and bending as well as warping distortion. Coupling between the two subdomains is realized by the Newton method in which an exact Jacobian matrix is derived by solving both fluid and structure tangent problems. The calculation is repeated until the solution reaches convergence. Thanks to the positive aspects of this implicit scheme, numerical instability related to the time integration can be avoided without relying on infinite frequency added mass, which is inevitable when an explicit scheme is used. Moreover, a direct integration scheme, such as the Newmark-β method, for structural problems can be used, and this formulation can be easily extended to the case with structural nonlinear effect, such as large deformation. The developed computer program is validated through comparison with published experimental data, ending up with good correspondence between the two results. Validation is also achieved through a comparative study on rigid body motion with an existing six degrees of freedom (6-DOF) ship motion program.
Multiobjective Optimization and Multiattribute Decision Making Study of Ship’s Principal Parameters in Conceptual Design
Authors: Xuebin Li
Published: January 2021

Numerous real-world problems relating to ship design are characterized by many alternatives as well as multiple conflicting objectives. Ship design is a complex endeavor requiring the successful coordination of many different disciplines, both technical and nontechnical. Conceptual design is the least defined stage of the ship design process and seeks to define the basic payloads and ship size characteristics. A hybrid approach for multiobjective optimization study of ship's principal parameters in conceptual design is proposed in the present analysis. In the first stage, a multiple objective genetic algorithm (MOGA) is employed to approximate the set of Pareto solution through an evolutionary optimization process. In the subsequent stage, a multiattribute decision making (MADM) approach is adopted to rank these solutions from best to worst and to determine the best solution in a deterministic environment with a single decision maker. A bulk carrier example, with 6 parameters, 3 criteria, and 14 constraints is conducted to illustrate the analysis process in present study. Pareto frontiers are obtained, and the ranking of the Pareto solution set is based on entropy weight and TOPSIS method. The ideal solution is compared with those from classic multiobjective methods.
Numerical and Experimental Investigation of Hydrodynamic Characteristics of Deformable Hydrofoils
Authors: Ducoin Antoine , Deniset François , Astolfi Jacques André , Sigrist Jean-François
Published: January 2021

The present paper is concerned with the numerical and experimental investigation of the hydroelastic behavior of a deformable hydrofoil in a uniform flow. The study is developed within the general framework of marine structure design and sizing. An experimental setup is developed in the IRENav hydrodynamic tunnel in which a cambered rectangular hydrofoil is mounted. An image-processing device enables the visualization of the foil displacement. As for the numerical part, the structure problem is solved with the finite element method, while the fluid problem is solved with the finite volume method using two distinct numerical codes that are coupled through an iterative algorithm based on the exchange of the boundary conditions at the fluid-structure interface. Results obtained from the coupled fluid-structure computations including deformation and hydrodynamic coefficients are presented. The influence of the fluid-structure coupling is evaluated through comparisons with "noncoupled" simulations. The numerical simulations are in very good agreement with the experimental results and highlight the importance of the fluid-structure coupling consideration. Particular attention is paid to the pressure distribution modification on the hydrofoil as a result of deformations that can lead to an advance of the cavitation inception, which is of paramount importance for naval applications.
An Experimental Method to Satisfy Dynamic Similarity Requirements for Model Submarine Maneuvers
Authors: Shen Young T. , Hess David E.
Published: January 2021

Dimensional analysis and dynamic similarity requirements show that Reynolds, Froude, and Strouhal scales are important parameters to be satisfied for free-running submarine model (FRM) maneuvering experiments so that they correctly represent full-scale behavior. The requirement that all three scales be satisfied simultaneously presents conflicting demands on the relationship between the velocity U and the characteristic length L of the model. The inability to meet these demands presents technical challenges to properly satisfy dynamic similarity for the FRM. Instead, we take a first-principles approach by considering the forces and moments acting on the vehicle and seek solutions that dynamically produce the same scaled forces and moments on the model as exist on the full-scale vehicle. Thus, this paper presents an extended dynamic similarity theory, introducing scaling formulas that have been derived from similarity solutions. These are applied to an unsteady turning maneuver of the FRM to suggest an improved experimental program. The improved approach will then dynamically satisfy the aforementioned three scaling parameters.
Nonlinear Computation of Water Impact of Axisymmetric Bodies
Authors: Yan Hongmei , Liu Yuming
Published: January 2021

A fully nonlinear numerical simulation based on a boundary element method was used to investigate water impact of axisymmetric bodies that strike vertically the horizontal free surface from the air. The main objective was to understand the gravity effect on flow/wave kinematics and dynamics and to quantify the range of validity of existing theories and computations that are based on the infinite Froude number assumption. Two body geometries were considered: inverted cone and sphere. For the inverted cone, we obtained detailed dependencies of free-surface profile and impact pressure and load on the body on the generalized Froude number (Fr(V/gt)1/2, where V is the impact velocity, g is the gravitational acceleration, and t is time) and deadrise angle a. Based on these, we developed an approximate formula for evaluating the contribution of the gravity effect to the total impact force on the body in terms of a similarity parameter Fr/a1/2. For the sphere, we developed and applied a pressure-based criterion to follow the evolution of flow separation on the body and to obtain an appropriate description of the free-surface profile near the body and accurate evaluation of the impact pressure and load on the body during the entire impact process. The numerical result of impact force on the body agreed well with existing experimental measurements. We confirmed that the gravity effect is unimportant in initial impact of the sphere. Significantly, we found that in a later stage of impact, flow separation remains at an almost fixed position at an angle u 62.5 deg to the bottom of the sphere for a wide range of Froude numbers, Fr V/(gR)1/2 1, where R is the radius of the sphere.
A Viscous/Inviscid Interactive Approach for the Prediction of Performance of Hydrofoils and Propellers with Nonzero Trailing Edge Thickness
Authors: Pan Yulin , Pan Yulin
Published: January 2021

A viscous/inviscid interactive (VII) approach is applied to predict the performance of hydrofoils and propellers with nonzero trailing edge thickness. The emphasis has been put on developing VII models for flow separation. The investigation starts from a two-dimensional (2D) hydrofoil. The current method uses an iterative scheme to find a nonlifting closing extension behind the trailing edge. Two kinds of schemes are applied for the iteration process:a non-lifting extension with 1 or 2 degrees of freedom, in fully wetted condition andan extension which is treated like a cavity surface, but with a nonconstant cavity pressure distribution. The results from these schemes are compared with those from a commercial RANS Solver (Fluent).

Next, the current schemes using flap extensions are extended to three-dimensional (3D) propeller flows. The 3D models are developed so that all the span-wise strips of the propeller satisfy similar conditions to those used in 2D. A propeller with significant nonzero trailing edge thickness is analyzed, using several 3D models, and the results are compared with existing experimental data.
A Method for Assessment of the Survival Time of a Ship Damaged by Collision
Authors: Schreuder Martin , Hogström Per , Ringsberg Jonas W. , Johnson Erland , Janson Carl Erik
Published: January 2021

Following an interdisciplinary calculation procedure, the chain of events of ship collision, flooding, and loss of stability within given time have been investigated. The method established in the current work concerns the interaction between structural and damage stability computations and has been used to study the influence of various parameters, for example, significant wave height and size of damage opening on a RoPax ferry damaged in a collision with a ship of similar size.
Physics-Based Learning Models for Ship Hydrodynamics
Authors: Weymouth Gabriel D. , Yue Dick K.P.
Published: January 2021

We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution high-fidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problemsat speed waterline profiles;ship motions in head seas; andthree-dimensional breaking bow waves. PBLM is shown to be robust and produce error rates at or below the uncertainty in the generated data at a small fraction of the expense of high-resolution numerical predictions.
Ship Hull Structural Multiobjective Optimization by Evolutionary Algorithm
Authors: Sekulski Zbigniew
Published: January 2021

An evolutionary algorithm for multiobjective optimization of the structural elements of the large spatial sections of ships is presented. The evolutionary algorithm where selection takes place based on the aggregated objective function combined with domination attributes as well as distance to the asymptotic solution is proposed and applied to solve the problem of optimizing structural elements with respect to their weight and surface area on a high-speed vehicle-passenger catamaran structure with several design variables such as plate thickness, scantlings of longitudinal stiffeners and transverse frames, and spacing between longitudinal and transversal structural members. Details of the computational models were at the level typical for conceptual design. Scantlings were analyzed using the selected rules of a classification society. The results of numerical experiments with the use of the developed algorithm are presented. They show that the proposed genetic algorithm can be a foundation of the effective multiobjective optimization tool for ship structure optimization. Further development of the tool should include more advanced methods for ship structural analysis.
Performance Decay Analysis of a Marine Gas Turbine Propulsion System
Authors: Altosole Marco , Campora Ugo , Martelli Michele , Figari Massimo
Published: January 2021

Marine propulsion plants are designed to be more and more efficient to minimize fuel consumption and pollution emissions. However, during the ship operating life, propulsion components and hull are characterized by a certain performance decay, responsible for a worse behavior of the overall propulsion plant. For this reason, the several propulsion components are periodically subjected to expensive maintenance works to restore, as far as possible, their original design characteristics. In the present study, the propulsive performance variation of a naval vessel, powered by a gas turbine as part of an innovative CODLAG system, is simulated and analyzed by means of a detailed and validated numerical code. A sensitivity analysis regarding the influence of the main components deterioration (gas turbine, propellers, and ship hull) on the overall behavior of the propulsion plant is carried out. Several speed profiles of the vessel have been analyzed in terms of the usual performance parameters (ship speed, engine power, and fuel consumption) as well as the pollution emissions of the gas turbine. The main aim of the work is to get useful information for the ship management and maintenance scheduling (condition-based maintenance).
Integrated Line of Sight and Model Predictive Control for Path Following and Roll Motion Control Using Rudder
Authors: Liu Cheng , Sun Jing , Zou Zaojian
Published: January 2021

Roll motion control and path following are two representative marine control problems that have been traditionally treated separately. However, these two problems are closely coupled, as roll motion could cause negative effects on marine surface vessels during path following in seaways and path following actions could cause undesirable roll motion. In this article, an optimal controller is proposed for the integrated path following and roll motion control problem. The rudder, whose actuation amplitude and rate are both limited, is the only control input, while the cross-track error, heading angle, roll rate, and roll angle are the outputs that collectively define the performance of the system. This leads to a classic underactuated problem. Model predictive control is the natural choice for the solution, given its capability in dealing with constraints and multi-input-multi-output system, and its design will be pursued in this article. Line of sight technique is used to extend the straight-line path following to arbitrary path following. A four degrees of freedom high-fidelity model is implemented as the simulation model, and the simulation results verify the effectiveness of the proposed controller. The influences of the control design parameters on system performance are investigated and the trade-offs between two key attributes, namely, the roll reduction and path following, are explored.
Large-Eddy Simulations of Submarine Propellers
Authors: Balaras Elias , Schroeder Seth , Posa Antonio
Published: January 2021

High-fidelity, eddy-resolving, simulations of marine propellers are challenging due to the coexistence of moving and stationary elements within the computational box, as well as the need to accurately resolve the dynamics of wake structures such as the tip and hub vortices, which have an effect on the acoustic signature of underwater vehicles. Although an isolated propeller in open-water conditions can be simulated in a rotating reference frame, in a computation involving the body of an appended submarine, e.g., the relative motion needs to be properly treated. This increases the computational cost and reduces the accuracy/robustness of typical body-fitted approaches. In this work, an immersed boundary formulation is utilized to perform large-eddy simulations of a propeller in open-water conditions and in the presence of an upstream appendage at zero incidence. In such case, the requirement for the grid to conform to the moving body is relaxed—solution is locally reconstructed to satisfy boundary conditions—and efficient, conservative structured solvers can be used. This enables us to capture the detailed dynamics of the tip vortices and their footprint on the statistics of the wake. The influence of the upstream appendage is also assessed.
High-Speed Ship Maneuverability
Authors: Yasukawa Hironori , Hirata Noritaka , Nakayama Yoshiyuki
Published: January 2021

In this paper, the effects of changes in hull attitude and the presence of stern append- ages such as rudders, shaft brackets, bossing, and propeller shafts on the maneuver- ability of a high-speed ship are investigated. The study is conducted for a ship operating within a Froude number range of 0.6–1.0. To determine the effect of attitude changes on the hydrodynamic derivatives during maneuvering, the hydrodynamic forces acting on the ship model with/without stern appendages are measured in three conditions: an even keel with the designed draft, and the same setup including hull rise or trim. For each condition, measurements are conducted for oblique motion, steady turning, and straight motion with heel, for various ship speeds. The hydro-dynamic derivatives excluding the attitude change are obtained from the measured results, along with the changes in these derivatives due to hull rise and trim. Using the hydrodynamic derivatives, the maneuverability indexes are calculated.
The Society’s Emblem
Authors: Forrest Matthew G.
Published: January 2021

The Emblem of the Society shall depict two concentric circles with the words "The Society of Naval Architects and Marine Engineers" between the circles, with the space inside the circles so designated as to depict the conventional symbol for the midship section of a ship, all as below. (Article III.)
Longitudinal Strength of Great Lakes Bulk Carriers
Authors: Vedeler Alex
Published: January 2021

Although little statistical information is available regarding the actual wave conditions on the Great Lakes, considerable reductions are possible in the required scantlings of the present and future Great Lakes bulk carriers. Utilizing the available knowledge about the strength of ocean-going vessels and modifying this for the Lakes, rational formulas are developed for the required midship section modulus and moment of inertia. The present Lake strength norm for the large carriers is a linear extrapolation of requirements developed almost 50 years ago and has led to a required midship section modulus considerably in access of what is necessary. The formulas developed in this paper indicate that a saving of around 15 percent in the steel weight is possible within the present state of the art. As more detailed information of the wave spectrum becomes available in the future, further savings should be possible.
Hydrodynamic Model Tests of Offshore Drilling Structures
Authors: Numata Edward
Published: January 2021

Model-basin facilities of Davidson Laboratory and experimental techniques for model tests of offshore drilling structures; general observations drawn from a decade of test experience in this field; use of techniques of spectral analysis for study of floating-platform motions in irregular seas are discussed in this paper.
Combination Bulk Carriers
Authors: Dorman W.J.
Published: January 2021

This paper is a state-of-the-art report on bulk carriers that carry both dry and liquid cargoes. There were approximately 96 vessels of this type in service in April 1966 and almost 50 others were building or contracted for at that time. All available characteristics of these vessels are tabulated in an Appendix and numerous sketches showing various designs are included. Hull proportions, cubic capacity versus deadweight ratios, ballast capacities, and structural arrangements of various types are compared. Freeboard assignment, Classification Society requirements, tonnage admeasurement, and Panama and Suez Canal requirements and restrictions are discussed. The use of various cargo spaces for both dry and liquid cargoes, changeover considerations, and associated problems of cleaning, cargo heating, ventilation, and ballasting are reviewed. Construction and operating costs are considered and some comparisons made with straight bulk carriers. The paper emphasizes the payload percentage of sea time and the ability of switching from a dry to a liquid cargo, or vice versa, as strong reasons for the growing popularity of this type.
Business and Technical Aspects of the Building of Cape Breton Miner
Authors: Staff _ , Staff _
Published: January 2021

The Cape Breton Miner has been in operation since June 1 964. This vessel has transported and self-unloaded coal from Nova Scotia and U. S. A., iron ore from Venezuela, Seven Islands' pellets, gypsum from Nova Scotia, and has recirculated grain through the unloading system in order to unload the grain from one hatch only. To operate successfully an unloading crew requires experience with each type of cargo in the particular vessel. The hull design, the boiler automation, the all-belt unloading feature can be considered completely successful. The sea speeds and performance in ocean storms has been as predicted from trial results. The Cape Breton Miner encountered a full gale in the North Atlantic in January 1965, experiencing winds gusting up to 80 mph. A large American liner suffered considerable damage from this same storm. A sistership Ontario Power was delivered to the owners in May 1965. The latter vessel is of the same hull design and includes all the features of the Cape Breton Miner. Several minor changes were introduced in order to better the unloading performance.
Utilization of Propeller Shrouds as Steering Devices
Authors: Gordon Samuel J. , Tarpgaard Peter T.
Published: January 2021

The utilization of nonsymmetric propeller shrouds to develop a force perpendicular to the propeller axis is explained and several possible applications and configurations are outlined. A theory is developed for the prediction of magnitude and direction of this side thrust. A specific application is made to a semicircular shroud used in place of a conventional rudder. Advantages predicted are a significant increase in turning force, together with complete elimination of rudder appendage drag and an increase in propulsive thrust of approximately 5 percent. Results of preliminary experimental investigation show that the theory gives a good approximation to actual results for thrust coefficients up to about 5.
Tug Propeller Design
Authors: Gokarn R. P.
Published: January 2021

The design of tug propellers is complicated because of the wide range of conditions in which a tug operates, and because of the difference in the power characteristics of the propeller and the engine. This paper describes methods, based on the KT — KQ coefficients, for designing tug propellers for various design conditions, and includes also a review of design data, and the calculation of optimum revolutions and power, and complete performance characteristics, with particular reference to the case of a constant-torque engine connected to a fixed-pitch propeller, either directly or through single-speed reduction gear.
An Analysis of Rigid Sidewall Surface Effect Craft for High-Speed Personnel Transportation
Authors: Miller Eugene R.
Published: January 2021

A number of commercial applications have been proposed for rigid sidewall surface effect craft. The transport of crews to offshore operations is an application which is well-suited to the immediate use of moderately sized craft of this type. Because the crews are paid while they are in transit, high speeds are required to minimize the total transportation costs. The characteristics and performance of rigid sidewall surface effect craft suitable for crew transport operations are developed. The major design parameters studied include pay-load, total power, and machinery type. Performance estimates are made for operations in both calm water and waves. An economic model is developed to simulate crewboat operations. Cost estimates are based on current technology and price levels. The total unit transportation cost is used as the economic criterion in the determination of the relative merit of various craft. For the purpose of comparison the characteristics and costs of planing hull crewboats for the same mission are developed. It is concluded that rigid sidewall surface effect craft have the potential of being economically superior to planing boats for crew transport operations.
Rules and Regulations for Bulk Grain Cargoes: Guidance for Preparing Documents for Approval Under 1969 Equivalent to Subchapter M
Authors: Middleton E. H. , Sammis S. F.
Published: January 2021

On October 28, 1969, the Assembly of the Intergovernmental Maritime Consultative Organization (IMCO) adopted new regulations as an equivalent to Chapter VI--Carriage of Grain--of the 1960 Safety of Life at Sea (SOLAS) Convention. The Assembly recommended that the Governments concerned accept the total application of the new grain regulations as being equivalent to and a total alternative to the provisions of the existing Chapter VI. The U. S. Coast Guard has adopted the equivalent and has published the requirements under Navigation and Vessel Inspection Circular No. 10–69.
Maneuvering Data: Intergovernmental Maritime Consultative Organization Maritime Safety Committee Recommendation
Authors: Price R. I.
Published: January 2021

International concern over increased risk of collision with increasing size and speed of vessels, especially collision with subsequent release of oil or dangerous chemicals, led the Assembly of the Intergovernmental Maritime Consultative Organization (IMCO) to recommend that maneuvering booklets be furnished masters of large vessels and those carrying bulk chemicals.
Tankers and the U. S. Energy Environmental Analysis
Authors: Porricelli Joseph D. , Keith Virgil F.
Published: January 2021

The United States is facing an energy problem. The range of solutions varies from "the advancement of technology at any cost" to "a reversion to a bucolic society." Many of these solutions, while solving the energy problem, create an associated ecological problem. This paper illustrates a method by which additional oil can be safely imported to the U. S. by a marine transportation system. This marine system actually reduces the transportation cost of providing this energy and, more importantly, reduces the ecological damage to the oceans and beaches when compared with existing systems. The prospect of increasing oil imports for the United States at six or seven times the rate experienced in the past decade adds a new dimension to U. S. external petroleum logistics, particularly with respect to tankers and port facilities to accommodate them. The paper is divided into four major areas:The U. S. energy situation and projected oil requirements;economics of tankers to import that oil to the U. S.;the environmental impact of tanker transportation systems upon the U. S.; andthe cost and effectiveness of those systems.
Effectiveness of Double Bottoms in Preventing Oil Outflow from Tanker Bottom Damage Incidents
Authors: Card James C.
Published: January 2021

Shortly after the Torrey Canyon stranding, worldwide public opinion began pressuring the maritime community for pollution-free tanker designs. Perhaps the most widely discussed pollution abatement design feature is the double bottom. In U. S. waters from January 1969 through April 1973 there occurred 30 pollution casualties that resulted from tanker bottom damage. The paper examines all these accidents to determine how effective double bottoms would have been in reducing their number as well as the amount of oil outflow. Results indicate that a double bottom whose height is one-fifteenth the beam could have been effective in preventing outflow in 27 of the 30 casualties examined.
VIDEC After One Year—Installation and Operation
Authors: McCarthy William L. , Wallace Richard P.
Published: January 2021

The Vibration Analysis and Deviation Concept (VIDEC), a computerized steam propulsion plant performance monitoring and failure prediction system, is presently operating on a new containership. This interim report is an attempt to document the history of this system from the concept development phase through fabrication, software design, in-plant simulation, shipyard installation, and initial shipboard operation. A brief system description including system concepts is presented. The paper concentrates on the system implementation, installation, and initial operation. A discussion is presented of types of data and concepts being evaluated and the methods of evaluation being used. Illustrations and tables of pertinent data are also included. The paper closes with a discussion of the VIDEC system and concept as they relate to other possible shipboard automation systems and programs. Finally, conclusions and recommendations are presented.
Small-Craft Power Prediction
Authors: Blount Donald L. , Fox David L.
Published: January 2021

A valid performance prediction technique for small craft is an invaluable tool not only for the naval architect, but also for the operators and builders. This presentation describes the methodology for making speed-power predictions for hard-chine craft of the types found in the offshore, military, and recreational applications. The distinct advantage of this method is that existing technical data have been organized into a logical approach, and areas of limited data have been overcome by the presentation of engineering factors based on model tests and full-scale trials of specific hull forms. This speed-power prediction method accounts for hull proportions, loading, appendage configuration, propeller characteristics (including c:avitation), and resistance augmentation due to rough water.
Closed Gas Turbine Engines for Future Marine Propulsion
Authors: Critelli F. , Pietsch A. , Spicer N.
Published: January 2021

The Maritime Administration, in its pursuit of improved economics and advanced technology, initiated a study which would evaluate new marine powerplants. It became quite apparent for several sound technical reasons that the closed-cycle gas turbine engine afforded an excellent opportunity for achievement of Mar-Ad's goal. This paper addresses the new-technology engine as applied to maritime ships, illustrating the advantages to shipowners and operators. Efficiency, multifuel capability, installation flexibility, reduction in ship's manning, as well as the overall reduced operating cost are highlighted in this paper.