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931.
The dynamic response of planing vessels in regular head seas is investigated numerically. Nonlinear time domain simulations
were performed using a 2D + t theory (two-dimensional plus time dependent theory). A prismatic hull form was assumed. We employed a two-dimensional (2D)
boundary element method to solve the initial boundary value problems in 2D cross planes, in which nonlinear free-surface conditions
and exact body boundary conditions were satisfied. At each time step, the total force and moment on the hull could be obtained
by using the sectional forces calculated in those 2D planes. Heave and pitch motions were then acquired by solving the equations
for those motions. The calculated heave and pitch responses were compared with the experiments by Fridsma (A systematic study
of the rough-water performance of planing boats. Davidson Laboratory Report R-1275, 1969) for two different Froude numbers. Three-dimensional (3D) corrections at the transom stern were applied to show the influence
of the 3D effect at the stern on the numerical results. Ship motions were affected by the 3D corrections, especially near
the resonance frequency, while the phase angles were slightly affected and the acceleration peaks at the bow near the resonance
frequency were sensitive to the 3D corrections. Other error sources in the theoretical results are also mentioned. 相似文献
932.
Manivannan Kandasamy Daniele Peri Seng Keat Ooi Pablo Carrica Frederick Stern Emilio F. Campana Philip Osborne Jessica Cote Neil Macdonald Nic de Waal 《Journal of Marine Science and Technology》2011,16(2):143-156
The wakes of high-speed passenger-only ferries that operated through Rich Passage, on the Seattle-Bremerton ferry route, caused
beach erosion and damage to habitat. A task was initiated to design a low-wake high-speed vessel using multi-fidelity CFD
based design optimization by using low-fidelity potential flow solvers for initial global design optimization and by using
URANS solvers for high-fidelity tuning of the optimized design. This simulation based design process involved a close collaboration
between ship designers, and hydrodynamics and CFD specialists, whose collective expertise guided the evolution of the design
based on both hydrodynamic and structural aspects. The initial hull shape optimization using potential flow code was carried
out by blending three different initial concepts provided by the designers. Subsequently, URANS was used to evaluate the potential
flow optimized hull and to further optimize the hull configuration parameters, namely, the centre-of-gravity, demihull spacing,
foil location, foil angle and slenderness ratio at different displacement conditions. The URANS based configuration optimization
also took into account the far field wakes’ energy spectrum with an objective of reducing the energetic, low frequency far
field wakes which are associated with beach flattening on the mixed sand and gravel beaches. Calculation of the far field
wake using URANS would require an unfeasibly large domain size; therefore, a Havelock code with a source distribution matching
the URANS calculated near field wave elevation was used to propagate the wakes into the far field. The end result of the optimization
was a design with significantly reduced far field wake, which is currently being built for experimental testing. 相似文献
933.
DongYoung Lee GyungNam Jo YunHo Kim Hang S. Choi Odd M. Faltinsen 《Journal of Marine Science and Technology》2011,16(3):323-330
In this paper, we investigated the effect of sloshing on the sway motions of two-dimensional rectangular cylinders in regular
waves, bearing in mind possible applications for LNG-FPSO and LNG-FSRU. First, we carried out experiments for two models with
different drafts, or the same draft but different filling ratios, in which the models were firmly connected to each other.
The sway motion was measured with a noncontact video camera. This is an extension of Rognebakke and Faltinsen’s work for a
single model (J Ship Res 47(3):208–221, 2003). It was found that the sway motion became small when the incident wave frequency was close to the lowest natural frequency
of each model. The sway motion greatly increased when the wave frequency was higher than this frequency. The measured data
were compared with numerical results obtained by a single-dominant multi-modal method; relatively good agreement was noted.
However, the numerical results deviated from the experimental results near the lowest natural frequency of the smaller model,
which was believed to be due to overturning waves, as observed during the experiment. Since this is out of the valid range
for the single-dominant multi-modal method, other, more appropriate, methods such as the multi-dominant modal method must
be applied instead. 相似文献
934.
We investigated the difference in fatigue behaviour between the aluminium alloys A5083-O and A5083-H321, which are used as structural components in ships and high speed craft. We obtained S–N curves for the base materials and the welded joints made of A5083-O. The relationships between the fatigue crack propagation rates and the stress intensity factor ranges ΔK, ΔK eff and ΔK RPG (Toyosada et al. in Int J Fatigue 26(9):983–992, 2004) were determined. Additionally, the evolution of fatigue crack growth for the base materials and the welded joints made of A5083-O was measured. We also carried out numerical simulations of fatigue crack growth for both base metals and their welded joints made of A5083-O. The difference in fatigue crack growth behaviour for each alloy and the validity of the numerical simulations of fatigue crack growth based on the RPG stress criterion (Toyosada et al. 2004) in the base materials and their welded joints was investigated. 相似文献
935.
Myeong-jo Son Sang Chul Lee Ki-chang Kwon Tae-wan Kim Rajiv Sharma 《Journal of Marine Science and Technology》2011,16(4):367-378
Ships are complex engineering structures that are designed and built on the basis of technical experience. A shipowner will
often be required to estimate the price of a new ship on the basis of the value of comparable ships identified in trade journals.
Similarly, shipbuilders are often interested in estimating approximate costs during the tendering phase in order to determine
whether a ship is likely to be competitive for a particular order. Thus, when designing a ship prior to having obtained a
contract, one of the most important processes is the estimation of approximate costs, including materials, associated labor,
and overhead. During this preliminary design phase, the design is temporary and subject to change based on variations in the
shipowner’s requirements. Hence, quick and flexible responses are key during this period and an integral aspect of the competitive
powers of the shipbuilder. Given this environment, we propose a “configuration estimation method.” Our method is based on
the configuration design method that is widely used in three-dimensional (3D) computer aided design (CAD) systems. We assume
that a product lifecycle management system is furnished and that the cost is then estimated via the configuration of the ship,
using an engineering bill of materials (E-BOM). In referring to the E-BOM, we utilize technical parametric costs derived from
similar ships built previously. Using the proposed method, it is possible to obtain an accurate list of materials from the
quotation, as well as a detailed work assessment for labor costs and overhead rates, so that reliable cost estimates can be
generated quickly and flexibly. To demonstrate the practical applicability and effectiveness of the proposed method, we implement
the prototype of a shipbuilding configuration estimation system by using a Microsoft Structured Query Language database and
an E-BOM from AVEVA Marine version 12.01, which is a representative CAD system for shipbuilding. 相似文献
936.
Hyun Park Nam Hyun An Nicholas Hutchins Kwing-So Choi Ho Hwan Chun Inwon Lee 《Journal of Marine Science and Technology》2011,16(4):390-401
An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first
devised by Hutchins and Choi (Proceedings of ASME FEDSM’02 2002 ASME Fluids Engineering Division Summer Meeting, Montreal)
and Hutchins (An investigation of larger-scale coherent structures in fully developed turbulent boundary layers, Hutchins
N (2003), PhD thesis, University of Nottingham). The reported drag reduction efficiency, which was as much as 30%, was quantified
only in terms of the reduction in the local skin-friction coefficient. The assessment of the drag reducing efficiency did
not take the side effects of the inclusion of the blades into considerations. Those effects are the increase in the wetted
surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements
in towing tank has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical
blades. It was found that for the case of h 4.0 × z 4.0 (h/δ = 1.04), the outer-layer vertical blades array achieved about 9.6% drag reduction without considering the increase in the
wetted surface area. A proper scaling method to give collapsed plot of drag reduction efficiency C
F/C
F0 was attempted, but the correlation remained limited. Of the two scaling methods, the outer scaling is found to be relevant
one. 相似文献
937.
Thomas Spenkuch Stephen R. Turnock Matteo Scarponi R. Ajit Shenoi 《Journal of Marine Science and Technology》2011,16(2):115-128
An approach for enhancing the realism of yacht fleet race simulations based on a lifting line method is developed. The wake
of an upwind sailing yacht is represented as a single heeled horseshoe vortex and image system. At each time step, changes
in vortex strength are convected into the wake as a pair of vortex line elements. These subsequently move in accordance with
the local wind, the self-induced velocity and the velocity induced by the presence of the wakes of other yachts. In addition,
the lifting line model has a model for the viscous wake due to the drag associated with the yacht and its sails superimposed
on it. A synthesis of sail yacht wake representations based on detailed 3D Reynolds-averaged Navier–Stokes computational fluid
dynamics calculations with wind tunnel test results is used to capture the initial strength of the combined main-jib vortex
system and its vertical height. The implementation of the lifting line algorithm within Robo-Race, a real-time yacht race strategy analysis tool, is described. Two upwind race interaction case studies are presented, and
these show that the newly implemented wake model makes an important contribution to enhancing the realism of the sailing simulation. 相似文献
938.
Moira L. McConnell 《WMU Journal of Maritime Affairs》2011,10(2):127-141
This paper begins by providing a brief overview of the International Labour Organization’s Maritime Labour Convention, 2006 (MLC, 2006), noting that this Convention, often called the “Seafarers’ bill of rights”, seeks to achieve both social and labour rights (“decent work”) for seafarers and fair competition (achieving a level-playing field) for shipowners. It has been described as the “fourth pillar” of the international maritime regulatory regime complementing the major International Maritime Organization conventions. The paper provides a brief update on international efforts to achieve the 30/33 formula needed to bring the Convention into force [at present, the tonnage element, 33% has been achieved already with coverage now at 54% of the world fleet (by gross tonnage), with 18 ratifications]. It then explores challenges faced by flag States in connection with capacity to implement the ship inspection and certification system under the MLC, 2006 and other difficulties with respect to legal implementation by the flag States. The paper also comments on some challenges in connection with port State, coastal State and labour-supplying State responsibilities. The paper points out that the MLC, 2006 is a comprehensive code that covers diverse issues and a wider range of both ships and seafarers than previous conventions. It often requires interdepartmental cooperation to implement its requirements at the national level. The paper concludes that, despite the slower pace of ratification in some regions, largely because of the recent economic and other crises, it appears that many actors in the maritime sector are already actively engaged in MLC, 2006 implementation, often ahead of governments. The question is not “if” but “when” the formula will be achieved to allow the MLC, 2006 to enter into force. 相似文献
939.
Michael Baldauf Knud Benedict Sandro Fischer Michael Gluch Matthias Kirchhoff Sebastian Klaes Jens-Uwe Schröder-Hinrichs Dana Meißner Ullrich Fielitz Erland Wilske 《WMU Journal of Maritime Affairs》2011,10(2):209-226
Safe ship handling in every situation and under all prevailing circumstances of ship status and the environment is a core
element contributing to the safety of the maritime transportation system. Especially in case of emergencies, there is a need
for quick, accurate and reliable information to manoeuvre a ship safely. This paper focusses on investigations into enhanced
response to maritime emergencies by means of onboard manoeuvring support. The research and discussions are done exemplarily
for person overboard (PoB) accidents. PoB is a typical situation for application of manoeuvring assistance and decision support,
e.g. in order to return quickly to the position of the accident. Based on the analysis of selected accident case studies and
existing solutions representing the technical state-of-the-art, shortcomings will be identified and discussed, and a potential
approach for advanced manoeuvring support in the context of e-Navigation-based requirements will be introduced and discussed. 相似文献
940.
“Big data” which admittedly means many things to many people is no longer confined to the realm of technology. Today it is a business imperative and is providing solutions to long-standing business challenges for banking and financial markets companies around the world. Financial services firms are leveraging big data to transform their processes, their organizations and the entire industry. Since 2012, the term “big data” has frequently been mentioned and used to describe and define the huge amount of data in the information explosive era and to name related technological development and innovation. As to the police work, the coming of big data era is not only a challenge but also an opportunity. Police agencies should go with the tide of development to start with such aspects as work thinking, top design, public information sharing and application and talent provision so as to promote the new development and progress of police work. This paper expounds the practical effect and significance of police big data application by cases happened in some areas. 相似文献