bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solving 2-D Slamming Problems by an Improved Higher-Order Moving Particle Semi-Implicit Method
Authors: Zha Ruosi , Peng Heather , Qiu Wei 
Published: January 2021

Abstract
A higher-order moving particle semi-implicit (MPS) method was further developed to solve 2-D water entry problems. To overcome the inconsistency in the original MPS methods, a pressure gradient correction was implemented to guarantee the first-order consistency of the gradient. The corrective matrix was modified by using the derivative of the kernel function. A particle shifting technique was also applied to improve the numerical stability. Validation studies were carried out for water entry of a rigid wedge with the tilting angles of 0, 10, and 20, and two rigid ship sections. Convergence studies were conducted on domain size, particle spacing, and time step. A particle convergence index method was proposed to evaluate numerical uncertainties in the improved MPS method. Uncertainties in numerical solutions due to spatial discretization were calculated. The predicted impact pressures and forces by the present method are in good agreement with experimental data.

Introduction
Slamming can cause local structural deformation and damages. It is important to solve highly nonlinear water-entry problems involving breaking free surfaces. Many studies on the impact of pressures/ loads during water entry or slamming have been performed using experiments, analytical solutions, and numerical simulations. Extensive drop tests have been conducted. For example, Bisplinghoff and Doherty (1952) carried out a series of experiments for free-fall wedges. Because ship motions in waves can lead to asymmetric water entry, wedges with different tilt angles were tested by Barjasteh et al. (2016). A more detailed review of studies based on theoretical, potential-flow, and computational fluid dynamics (CFD) methods is presented in the work of Peng and Qiu (2018).
A Holistic Approach to Ship Design: Tools and Applications
Authors: Papanikolaou Apostolos , Harries Stefan , Hooijmans Patrick , Marzi Jochen , Le Néna Romain , Torben Sverre , Yrjänäinen Antti , Boden Brigitte 
Published: January 2021

The present article introduces a holistic approach to ship design, as it is being developed in the Horizon 2020 EU project HOLISHIP (www.holiship.eu). The project deals with the development of design and virtual prototyping simulation platforms, which integrate software tools for all major ship design disciplines and optimization objectives, namely, building and operational cost, energy efficiency, safety, environmental footprint, and life cycle cost/impact assessment. It enables the seamless mathematical multi-objective optimization of ship design with governing design constraints and the exploration of the huge design space by parametric modeling of the ship design system and its components. The article outlines the integration of the essential software tools into the software platform and demonstrates the functionality and benefits of the HOLISHIP approach by brief presentations of typical case studies.

Introduction
The pattern of seaborne trade and goods transportation is changing, and so do the vessels of transportation. They need to adapt to changes in customer and market requirements, changes in cargo types and volumes, and new legislation for the safety of ships and the protection of the marine/aerial environment. Increased requirements for energy efficiency and the control of GHG emissions and the inherent uncertainties regarding fuel cost and future types of marine fuels pose extra challenges. This calls for significant advances in the approach to ship design and operation to meet continuously changing requirements over ship’s life cycle by holistic, efficient, and easy-to-use design procedures and software systems.
The Establishment of Shipbuilding Construction Tolerances
Authors: Butler J. D. , Warren T. R. 
Published: January 2021

Abstract
Predictable and economically achievable construction tolerances are a prerequisite for the establishment of effective shipbuilding procedures, as unproductive rework and on-the-job fit-ups are the alternative. This paper reviews the factors to be considered in the development of tolerances and suggests the use of variation-merging equations and variation simulation as techniques that can be used to formulate a practical system of tolerances.
Automatic Programming System for Shipyard Robots
Authors: McGhee Scott , Nalluri Sivrama , Reeve Ron , Rongo Robert , Prinz Fritz , Hemmerle Jim 
Published: January 2021

The application of robots to variable tasks in unstructured environments presents a series of problems that must be solved in order to achieve viable results Common teaching-type robots cannot be applied in these cases as the programming time and labor investment far exceed the time and cost of direct manual production. Numerically controlled (NC) robots programmed off-line by modified NC methods have been applied with economic success to program robots directly from computer-aided design (CAD) data where tasks are sufficiently repetitive and the operating environment is sufficiently structured Similarly, off-line programming systems have been developed by various robot manufacturers to generate instructions from CAD data for their robots. Likewise, developers of 3D simulation software have devised methods to merge CAD data with physical models of robots and system hardware to produce robot path programs that approximate the tasks to be performed. Each of these systems is unable to provide a totally automated means to program robot tasks directly from CAD data due to inaccuracies in the real-world elements and/or the models, and due to a lack of knowledge about the processes. A new approach to automatic robot programming is needed that is capable of dealing with:inherent differences between the CAD models and the real-world parts;uncertainties regarding the precise location and accessibility of the parts relative to the robot:process knowledge required to adapt these differences and uncertainties; andprocess knowledge essential to optimizing robot activities.
Such an automatic robot programming system is being developed to meet the dual-use defense and commercial ship construction needs of American shipyards under the Technology Reinvestment Project (TRP) for Shipbuilding Robotics. This system automates the programmer's task of identifying location of welds, assigning weld process parameters and adaptive welding strategies to each joint. A procedural diagram for this system is shown in Figure 1. The results and benefits of this approach are described herein. Fig. 1Procedure for automatic off-line robot task planning
Microstructure and Mechanical Properties of GTAW Welded Joint of Invar Alloy
Authors: Zhao DongSheng , Zhang TianFei , Wu LiangLiang , Kong LeLe , Liu YuJun 
Published: January 2021

Experiment of automatic gas tungsten arc welding of liquefied natural gas carrier Invar alloy with a thickness of .7 mm was completed, and the welding parameters were optimized, as well as microstructure and mechanical properties of the welded joint were measured and analyzed. The grain size of the area near the weld centerline was small, mainly cellular dendrites, and the grain size on both sides of the weld centerline increased gradually, mainly dendrites, whereas the grain size near fusion line was larger, and there were more columnar crystals. The heat-affected zone was composed of coarse austenite grains. Transgranular cracks were the main cracks in the welding seam. When welding current was 40 A, frequency was 120 Hz, and welding speed was 350 mm/min, tensile strength of the welded joint was 446.9 MPa, which 88.1% of the base metal’s tensile strength and 10.3% of the fracture elongation. The fracture surface of tensile specimens showed typical plastic fracture characteristics, with no obvious crack characteristics, and no eutectic liquid films were observed.

Introduction
Invar alloy is a Fe–36%Ni alloy. Its thermal expansion coefficient at room temperature is less than 1.6X10-6/k, which is about one-tenth of that of low carbon steel, and changes little in a larger temperature range. Therefore, Invar alloy is widely used in making precision measuring instruments and low temperature-resistant materials (Corbacho et al. 1998; Park et al. 2011; Qiu et al. 2016; Yakout et al. 2018). In recent years, with the increasing demand for clean energy, liquefied natural gas (LNG) carriers are developing rapidly (Zhao et al. 2015; Oh et al. 2018). LNG liquefies at temperatures below -161.5°C. The volume of LNG is about 1/ 625 of the volume of gaseous natural gas of the same mass; thus, it can transport large quantities of natural gas over long distances.
Recent Contributions Under the Bureau of Ships Fundamental Hydromechanics Research Program
Authors: St. Denis M. , Craven J.P. 
Published: January 2021

The third main nautical objective, Seakeeping, refers to that aspect of ship performance in which the seaway enters in a dominant manner and affects fundamentally the character of the problem. In the section on Control [3],1 a pattern was introduced according to which seakeeping was related to the uncontrolled as well as the controlled oscillations which take place with reference to a ship's inertial system. But, more broadly speaking, seakeeping includes all of the following subjects:Description of the seaway.Determination of the forces imposed by the seaway on the vessel—the excitation (hydrodynamic loadings, wave bending moment, slamming forces, and so on).Determination of the response of the ship in her six degrees of freedom (ship motions).Prediction of the perils to which a ship may be exposed (capsizing, foundering, safety at sea).Prediction of the loss in speed she will sustain in heavy weather.Evaluation of the amount of stabilization necessary to prevent unacceptable or undesirable displacements and accelerations.
The elastic response and strength of a vessel's structure, though not included under seakeeping, depend, nevertheless, in an essential manner thereon.
A Theory for the Plastic Design of Ship Plating Under Uniform Pressure
Authors: Wah Thein 
Published: January 2021

A theoretical investigation is made of the behavior of a long rectangular plate loaded laterally beyond the elastic range of the material. The study takes into account the effects of the following phenomena:Initial deflections;initial locked-in moments; anddisplacements of the edges, in the plane of the plate.
The proposed method permits the design of plates based on allowable deflections under working loads and allowable permanent sets.
Charts for Estimating Nonlinear Hogging and Sagging Bending Moments
Authors: Mansour A. E. , Wasson J-P. 
Published: January 2021

Abstract
This paper presents charts for preliminary estimates of the nonlinearities associated with wave bending moments acting on a ship moving in a stationary sea. Deviation of the actual hull shape above the waterline from "vertical wall" is characterized by a flare coefficient. The charts show the influence of the flare coefficient, among other parameters, on a nonlinearity parameter which may be used to estimate the difference between wave hogging and sagging moments. Three application examples are given at the end of the paper to illustrate how the charts can be used in conjunction with linear strip theory results in order to estimate slightly nonlinear hogging and sagging moments.
Application of Reynolds-Stress Transport Models to Stern and Wake Flows
Authors: Sotiropoulos F. , Patel V. C. 
Published: January 2021

ABSTRACT
The Reynolds-averaged Navier-Stokes equations are solved to assess the importance of the turbulence model in the prediction of ship stern and wake flows. Solutions are obtained with a two-equation scalar turbulence model and a seven-equation Reynolds-stress tensor model, both of which resolve the flow up to the wall, holding invariant all aspects of the numerical method, including solution domain, initial and boundary conditions, and grid topology and density. Calculations are carried out for two tanker forms used as test cases at recent workshops, and solutions are compared with each other and with experimental data. The comparisons reveal that the Reynolds-stress model accurately predicts most of the experimentally observed flow features in the stern and near-wake regions whereas the two-equation model predicts only the overall qualitative trends. In particular, solutions with the Reynolds-stress model clarify the origin of the stern vortex.
Effects of Ship Hull and Propeller on Rudder Cavitation
Authors: Shen Young T. , Remmers Kenneth D. , Jiang Chen W. 
Published: January 2021

Ship trial observation and drydock inspection of a surface ship combatant show that rudder cavitation can be a real problem in terms of ship operation and maintenance. A project has been initiated by the Navyto identify fleet rudder cavitation problem,to investigate experimentally and numerically hull/propeller effects on rudder cavitation, andto develop methods to incorporate propeller/rudder interaction into the future rudder design for cavitation improvement.
Experiments were carried out at the Navy's Large Cavitation Channel (LCC) with a geosim model of a fleet rudder, propeller and ship hull of a surface combatant. Two-component Laser DopplerVelocimetry (LDV) was used to measure the field velocity and inflow angles in the propeller slipstream. A dynamometer and pressure taps were used to measure rudder lift, drag and pressure distributions. Influence of the ship hull and propeller on rudder forces, pressure distribution, and cavitation performance are compared with numerical calculations. The resemblance between the model rudder cavitation pattern in the LCC and full-scale cavitation erosion pattern observed in the dry dock is discussed.
A Simplified Method to Predict the Added Resistance of a SWATH Ship in Waves
Authors: Fang Ming-Chung 
Published: January 2021

A simplified method called phase transfer is used to calculate the added resistance of a SWATH ship advancing in regular waves. Using the method, the total added resistance of the twin-hull body can be obtained by calculating the corresponding hydrodynamic forces of a single body only. There is no need to calculate the force on each body twice, and the hydrodynamic interactions are not included. The strip theory is still used and the nonlinear force prediction is based on the theory for a monohull ship advancing in waves. Two additional assumptions are also made:the hull body is a "weak scatterer" andthe second-order potential is small and can be neglected.
Practically, the present method is suitable for predicting the corresponding hydrodynamic properties of a SWATH ship with high speed because the hydrodynamic interactions are not significant. The results obtained in the paper mostly agree with the experimental data and show that the present idea is reasonable. It is also found that the inclusion of the interaction between two hulls may lead to some unreasonable negative added resistance in bow waves. Therefore, the method developed here can be considered as a simpler tool to analyze the added resistance for SWATH ships advancing in waves, especially for higher speed.
The Effect of the Steady Flow Potential on the Motions of a Moving Ship in Waves
Authors: Fang Ming-Chung 
Published: January 2021

A three-dimensional method to analyze the motions of a ship running in waves is presented, including the effects of the steady-flow potential. Basically, the general formulations are based on the source distribution technique by which the ship hull surface is regarded as the assembly of many panels. The present study includes three algorithms for treating the corresponding Green function:the Hess & Smith algorithm for the part of simple source I/r,the complex plane contour integral of the Shen & Farell algorithm for the double integral of steady flow, andthe series expansions of the Telste & Noblesse algorithm for the Cauchy principal value integral of unsteady flow.
The study reveals that the effect of steady flow on ship motions is generally small, but it still cannot be neglected in some cases, especially for the ship running in oblique waves. The effect also depends on the fore-aft configuration of the ship. The results predicted by the present method are found to be in fairly good agreement with existing experiments and other theories.
Numerical Analysis of 2-D and 3-D Cavitating Hydrofoils Under a Free Surface
Authors: Bal Sakir , Kinnas Spyros A. , Lee Hanseong 
Published: January 2021

A method which models two- or three-dimensional cavitating hydrofoils moving with constant speed under a free surface is described. An integral equation is obtained by applying Green's theorem on all surfaces of the fluid domain. This integral equation is divided into two parts:the cavitating hydrofoil problem, andthe free-surface problem.
These two problems are solved separately, with the effects of one on the other being accounted for in an iterative manner. The cavitating hydrofoil surface and the free surface are modeled with constant strength dipole and source panels. The source strengths on the free surface are expressed in terms of the second derivative of the potential with respect to the horizontal axis by applying the linearized free-surface conditions. The induced potential by the cavitating hydrofoil on the free surface and by the free surface on the hydrofoil are determined in an iterative sense. In order to prevent upstream waves the source strengths from some distance in front of the hydrofoil to the end of the truncated upstream boundary are enforced to be equal to zero. No radiation condition is enforced at the downstream boundary or at the transverse boundary. The method is applied to 2-D and 3-D hydrofoil geometries in fully wetted or cavitating flow conditions and the predictions are compared with those of other methods in the literature.
Computational Fluid Dynamics–Based Optimization of a Surface Combatant
Authors: Tahara Y. , Stern F. , Himeno Y. 
Published: January 2021

Computational fluid dynamics (CFD)-based optimization of a surface combatant is presented with the following main objectives:development of a high-performance optimization module for a Reynolds averaged Navier-Stokes (RANS) solver for with-free-surface condition; anddemonstration of the capability of the optimization method for flow- and wave-field optimization of the Model 5415 hull form.
The optimization module is based on extension of successive quadratic programming (SQP) for higher-performance optimization method by introduction of parallel computing architecture, that is, message passing interface (MPI) protocol. It is shown that the present parallel SQP module is nearly m(= 2k+ 1; k is number of design parameters) times faster than conventional SQP, and the computational speed does not depend on the number of design parameters. The RANS solver is CFDSHIP-IOWA, a general-purpose parallel multiblock RANS code based on higher-order upwind finite difference and a projection method for velocity-pressure coupling; it offers the capability of free-surface flow calculation. The focus of the present study is on code development and demonstration of capability, which justifies use of a relatively simple turbulence model, a free-surface model without breaking model, static sinkage and trim, and simplified design constraints and geometry modeling. An overview is given of the high-performance optimization method and CFDSHIP-IOWA, and results are presented for stern optimization for minimization of transom wave field disturbance; sonar dome optimization for minimization of sonar-dome vortices; and bow optimization for minimization of bow wave. In conclusion, the present work has successfully demonstrated the capability of the CFD-based optimization method for flow- and wave-field optimization of the Model 5415 hull form. The present method is very promising and warrants further investigations for computer-aided design (CAD)-based hull form modification methods and more appropriate design constraints.
Hydrodynamic Testing of a High Performance Skiff at Model and Full Scale
Authors: Day A. H. , Cameron P. , Dai S. 
Published: January 2021

Abstract:
This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day & Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented.
The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction.
In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.