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1.
Alexander H. Day David Clelland Lawrence J. Doctors 《Journal of Marine Science and Technology》2009,14(3):387-397
This paper covers an extension of the study of Doctors et al. (J Ship Res 52(4):263–273, 2008) on oscillations in wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model to
the case of relatively shallow water. We demonstrate here that the unsteady effects are very prominent and that it is essentially
impossible to achieve a steady-state resistance curve in a towing tank of typical proportions for a water-depth-to-model-length
ratio of 0.25. This statement is particularly true in the speed region near a depth Froude number of unity. However, on the
positive side, we show here that an application of unsteady linearized wave-resistance theory provides an excellent prediction
of the measured total resistance, when one accounts for the form factor in the usual manner. Finally, a simple application
of the results to the planning and analysis of towing-tank tests is presented. 相似文献
2.
结合加油船的结构、使用特点,对海上加油过程中船舶的受力进行分析,仿真研究加油船稳定性与极限风速及浪速之间的关系,确定安全加油过程的极限风速及浪速,为恶劣天气下的加油提供指导及建议,对规范供油船行业行为具有积极的现实意义与工程应用价值. 相似文献
3.
Time-varying coefficient vector autoregressive (T-VVAR) modeling with instantaneous responses is applied to spectrum analysis
based on the nonstationary motion data of ships. Because of the ship's maneuvers, changes such as course and speed, the ship
motions in waves are regarded as a nonstationary random process, although the seaway can be considered as a stationary stochastic
process. The T-VVAR model is transformed into a state space model, and the time-varying coefficients can be evaluated by using
the Kalman filter algorithm. Using the estimated time-varying coefficients, the instantaneous cross spectra of the ship motions
can be calculated at every moment. In order to examine the reliability of the proposed procedure, on-board tests were carried
out. Under stationary conditions, at a constant speed and course, the proposed method shows good agreement with stationary
vector autoregressive (SVAR) modeling analysis. Moreover, it is confirmed that the proposed method can estimate the instantaneous
cross spectra of the ship motions even under nonstationary conditions, showing that this is a powerful tool for on-line analysis
of the nonstationary motion data of ships.
Received: August 2, 2002 / Accepted: November 28, 2002
Acknowledgments. The authors thank the captain and crew of the training ship Shioji Maru, Tokyo University of Mercantile Marine.
Address correspondence to: T. Iseki (iseki@ipc.tosho-u.ac.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;190:161–168) 相似文献
4.
Jasna Prpić-Oršić Roberto Vettor Odd Magnus Faltinsen Carlos Guedes Soares 《Journal of Marine Science and Technology》2016,21(3):434-457
The influence of various parameters, such as ship initial speed (full ahead and lower engine loads), loading condition, heading angle and weather conditions on ship fuel consumption and CO2 emission is presented. A reliable methodology for estimating the attainable ship speed, fuel consumption and CO2 emission in different sea states is described. The speed loss is calculated by taking into account the engine and propeller performance in actual seas as well as the mass inertia of the ship. The attainable ship speed is obtained as time series. Correlation of speed loss with sea states allows predictions of propulsive performance in actual seas. If the computation is used for weather routing purposes, values for various ship initial speed, loading conditions and heading angles for each realistic sea‐state must be provided. The voluntary speed loss is taken into account. The influence of the ship speed loss on various parameters such as fuel consumption and CO2 emissions is presented. To illustrate the presented concept, the ship speed and CO2 emissions in various routes of the Atlantic Ocean are calculated using representative environmental design data for the track of the routes where the ship will sail. 相似文献
5.
Self-propulsion computations using a speed controller and a discretized propeller with dynamic overset grids 总被引:2,自引:0,他引:2
Pablo M. Carrica Alejandro M. Castro Frederick Stern 《Journal of Marine Science and Technology》2010,15(4):316-330
A method that can be used to perform self-propulsion computations of surface ships is presented. The propeller is gridded
as an overset object with a rotational velocity that is imposed by a speed controller, which finds the self-propulsion point
when the ship reaches the target Froude number in a single transient computation. Dynamic overset grids are used to allow
different dynamic groups to move independently, including the hull and appendages, the propeller, and the background (where
the far-field boundary conditions are imposed). Predicted integral quantities include propeller rotational speed, propeller
forces, and ship’s attitude, along with the complete flow field. The fluid flow is solved by employing a single-phase level
set approach to model the free surface, along with a blended k−ω/k−ɛ based DES model for turbulence. Three ship hulls are evaluated: the single-propeller KVLCC1 tanker appended with a rudder,
the twin propeller fully appended surface combatant model DTMB 5613, and the KCS container ship without a rudder, and the
results are compared with experimental data obtained at the model scale. In the case of KCS, a more complete comparison with
propulsion data is performed. It is shown that direct computation of self-propelled ships is feasible, and though very resource
intensive, it provides a tool for obtaining vast flow detail. 相似文献
6.
Hiroshi Matsukura Maytouch Udommahuntisuk Hiroyuki Yamato A. A. B. Dinariyana 《Journal of Marine Science and Technology》2010,15(1):34-43
This research discusses domestic feeder container transportation connected with international trades in Japan. Optimal round
trip courses of container ship fleet from the perspective of CO2 emission reduction are calculated and analyzed to obtain basic knowledge about CO2 emission reduction in the container feeder transportation system. Specifically, based on the weekly origin–destination (OD)
data at a hub port (Kobe) and other related transportation data, the ship routes are designed by employing a mathematical
modeling approach. First, a mixed integer programming model is formulated and solved by using an optimization software that
employs branch and bound algorithm. The objective function of the model is to minimize the CO2 emission subject to necessary (and partially simplified) constraints. The model is then tested on various types of ships
with different speed and capacity. Moreover, it is also tested on various waiting times at hub port to investigate the effect
in CO2 emission of the designated fleet. Both the assessment method of container feeder transportation and the transportation’s
basic insights in view of CO2 emission are shown through the analysis. 相似文献
7.
This paper presents the uncertainty modelling of experimental results for a physical model of a tanker moored to a terminal inside a port. The physical model was built for an oil terminal at the port of Leixões in Portugal. The model incorporates the new modified port layout, as well as a future 300 m extension of the port outer north breakwater to enhance operational conditions. The physical model tests were performed on a scale of 1:80 in the Portuguese Civil Engineering Laboratory (LNEC). A generic mooring system of four mooring lines and two fenders is simulated using a nonlinear spring system. Decay tests are carried out to evaluate the natural periods of the moored model. Then, tests are carried out for the moored model in waves. The major aim of the experimental study is to obtain novel results for the wave elevation and direction at various locations inside the port, the ship motions at six degrees of freedom, and loads on mooring lines and fenders including the modified port layout. As the physical model measurements are subjected to different types of uncertainties, a systematic uncertainty analysis is carried out here, following ITTC guidelines and recommendations, to quantify all possible sources of uncertainties. The results are discussed, and several conclusions are reached. Based on the experimental results, the presented physical model study may replicate the results for waves and motions with uncertainties less than 9% of the significant amplitudes. The assessment of the applied nonlinear spring model reveals load predictions on the moorings, with uncertainties less than 4% of the maximum mooring loads. 相似文献
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10.
Lateral drift occurs due to the effects of wind forces, wave drifting forces, or both on ships sailing in actual seas. It
is important therefore to investigate the influence of lateral drift on seakeeping performance for improved ship operation.
The velocity potential was expanded as an asymptotic power series in terms of the lateral speed parameter, τ, defined as ω
e
V
0/g, where ω
e
is the frequency of wave encounter; V
0 denotes the lateral velocity, which is assumed to be sufficiently small; and g is the acceleration due to gravity. By combining this technique with the strip method, two sets of motion equations of all
the hydrodynamic force coefficients for ship seakeeping were derived. The first set is for ships without lateral drift and
is the same as the equations in the new strip method, and the second set is for the additional motions induced by lateral
drift. It was found that all ship motion modes except surge are coupled when a ship drifts laterally in waves. 相似文献
11.
Yusuke Tahara Joseph Longo Frederick Stern 《Journal of Marine Science and Technology》2002,7(1):17-30
This paper presents comparisons of computational and experimental fluid dynamics results for boundary layers, wakes, and
wave fields for the Series 60 C
B= 0.6 ship model in steady drift motion. The numerical method solves the unsteady Reynolds-averaged Navier–Stokes and continuity
equations with the Baldwin–Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary
conditions, and a body/free-surface conforming grid. The experimental and computational conditions, i.e., Froude numbers of
0.16 and 0.316 for the experiments, and Froude numbers of 0 and 0.316 for the computations, allow comparisons of low and high
Froude number results, respectively, which allows an evaluation of Froude number effects and validation of the computational
fluid dynamics at both low and high Froude numbers. This article gives an overview of this numerical approach, and the computational
conditions and uncertainty analysis are described. Results are presented for the wave and flow fields, with emphasis on the
important flow features of drift- and wave-induced effects in comparison with the experiments. Finally, conclusions from the
present study are given, together with recommendations for future work.
Received: August 31, 2001 / Accepted: March 25, 2002 相似文献
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This article presents a nonlinear time-domain simulation method for the prediction of large-amplitude motions of a Ro–Ro
ship in regular oblique waves in an intact and a damaged condition. Numerical computations and model tests have been carried
out to investigate the dynamic motion responses of Ro–Ro ship Dextra to various wave amplitudes at three different wave headings. The results of numerical and experimental investigations for
stern quartering waves are reviewed. Comparisons between predictions and measurements show good agreement except in the roll-resonant
region. Nonlinear effects are significant in horizontal modes of motion, and resonant roll motion, and there is strong coupling
between all modes of motion in the roll-resonant region for large-amplitude responses. On the other hand, the time-domain
simulation technique suffers from numerical drift in horizontal modes of motion as wave amplitude increases. This is due to
nonlinear equations of motion and the lack of a restoring force and moment in horizontal motion.
Received: April 30, 2002 / Accepted: August 9, 2002
Acknowledgments. II Programme of the European Community Commission under contract No. BRPR-CT97-0513.
Address correspondence to: H.S. Chan (hoi-sang.chan@ncl.ac.uk) 相似文献
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An efficient method for calculation of the slamming pressures on ship hulls in irregular waves is presented and validated
for a 290-m cruise ship. Nonlinear strip theory was used to calculate the ship–wave relative motions. The relative vertical
and roll velocities for a slamming event were input to the slamming calculation program, which used a two-dimensional boundary
element method (BEM) based on the generalized 2D Wagner formulation presented by Zhao et al. To improve the calculation efficiency,
the method was divided into two separate steps. In the first step, the velocity potentials were calculated for unit relative
velocities between the section and the water. In the next step, these precalculated velocity potentials were used together
with the real relative velocities experienced in a seaway to calculate the slamming pressure and total slamming force on the
section. This saved considerable computer time for slamming calculations in irregular waves, without significant loss of accuracy.
The calculated slamming pressures on the bow flare of the cruise ship agreed quite well with the measured values, at least
for time windows in which the calculated and experimental ship motions agreed well. A simplified method for calculation of
the instantaneous peak pressure on each ship section in irregular waves is also presented. The method was used to identify
slamming events to be analyzed with the more refined 2D BEM method, but comparisons with measured values indicate that the
method may also be used for a quick quantitative assessment of the maximum slamming pressures. 相似文献
18.
A computational method for improving hull form in shallow water with respect to wave resistance is presented. The method involves coupling ideas from two distinct research fields: numerical ship hydrodynamics and nonlinear programming techniques. The wave resistance is estimated by means of Morinos panel method, which is extended to free surface flow and considers the influence of finite depth on the wave resistance of ships. This is linked to the optimization procedure of the sequential quadratic programming (SQP) technique, and an optimum hull form can be obtained through a series of iterations giving some design constraints. Sinkage is an important factor in shallow water, and this method considers sinkage as a hydrodynamic design constraint. The optimization procedure developed is demonstrated by selecting a Wigley (C
B = 0.444) hull and the Series 60 (C
B = 0.60) hull, and new hull forms are obtained at Froude number 0.316. The Froude number specified corresponds to a lower than critical speed since most of the ships operating in shallow water move below their critical speed. The numerical results of the optimization procedure indicate that the optimized hull forms yields a reduction in wave resistance. 相似文献
19.
Ship hull deformation is one of the most significant influences on propulsion shafting alignment. Based on the calculation fundamentals of ship hull deformations, a new method of shafting alignment considering ship hull deformations is proposed in this paper. Ship loadings, wave loads and environment temperature differences in some extreme conditions, as well as elastic constraints, are simulated and applied to the finite element model of 76,000 DWT product oil tanker, so that ship hull deformations can be solved. Then, the deformations of the double bottom are converted to bearing offsets, which behave as boundary constraints for shafting alignment calculations. Taking the condition of light ship in calm water as a reference, the impact of hull deformations on shafting alignment is analyzed and optimized shafting alignment considering ship hull deformations is realized. 相似文献
20.
This article presents a study on the accuracy of the numerical determination of the friction and pressure resistance coefficients
of ship hulls. The investigation was carried out for the KVLCC2 tanker at model- and full-scale Reynolds numbers. Gravity
waves were neglected, i.e., we adopted the so-called double-model flow. Single-block grids with H–O topology were adopted
for all the calculations. Three eddy viscosity models were employed: the one-equation eddy viscosity and the two-equation
models proposed by Menter and the TNT version of the two-equation k-ω model. Verification exercises were performed in sets of nearly geometrically similar grids with different densities in the
streamwise, normal, and girthwise directions. The friction and pressure resistance coefficients were calculated for different
levels of the iterative error and for computational domains of different size. The results show that on the level of grid
refinement used, it is possible to calculate the viscous resistance coefficients in H–O grids that do not match the ship contour
with a numerical uncertainty of less than 1%. The differences between the predictions of different turbulence models were
larger than the numerical uncertainty; however, these differences tended to decrease with increases in the Reynolds number.
The pressure resistance was remarkably sensitive to domain size and far-field boundary conditions. Either a large domain or
the application of a viscous–inviscid interaction procedure is needed for reliable results.
This work was presented in part at the International Conference on Computational Methods in Marine Engineering—MARINE 2007,
Barcelona, June 3–4, 2007. 相似文献