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1.
Naoya Umeda Akihiko Matsuda Masami Hamamoto Shiro Suzuki 《Journal of Marine Science and Technology》1999,4(2):45-57
A systematic method for assessing intact ship stability with a free-running model in a seakeeping and maneuvering basin is
proposed in this paper. Model experiments were carried out in extremely steep regular waves for a model drifting, running
in head seas, and quartering seas. This method was applied to two purse seiners, and efficiently identified thresholds in
metacentric heights for capsizing of these ships. These capsizing thresholds are compared with requirements of the IMO Code
on Intact Stability. This series of model experiments also confirms that capsizing at the threshold occurs only in quartering
seas, and shows that capsizing is caused by broaching, loss of stability on a wave crest, or bow diving.
Received for publication on Jan. 20, 1999; accepted on July 6, 1999 相似文献
2.
By utilizing a four-degrees-of-freedom numerical model with dense grids of control parameters and the sudden-change concept,
the qualitative aspects of the nonlinear motions of a fishing vessel complying with the International Maritime Organization's
intact stability criteria in following and quartering seas were intensively explored. As a result, capsizing due to broaching,
capsizing without broaching, broaching without capsizing, stable surf-riding, and steady periodic motion were identified.
The natures of the boundaries of these motions in the control parameter plane were investigated, and the effects of the initial
conditions and the nonlinearity of calm-water maneuvering forces are also discussed. Furthermore, comparisons with a model
experiment showed that the numerical model used here qualitatively explains capsizing phenomena, but quantitatively overestimates
the danger of capsizing.
Received: June 11, 2001 / Accepted: October 9, 2001 相似文献
3.
In order to develop design and operational criteria to be used at the International Maritime Organization (IMO), critical
conditions for broaching are explored in the light of bifurcation analysis. Since surf-riding, which is a prerequisite to
broaching, can be regarded as a heteroclinic bifurcation, one of global bifurcations, of a surge-sway-yaw-roll model in quartering
waves, the relevant bifurcation condition is formulated with a rigorous mathematical background. Then an efficient numerical
solution procedure suitable for tracing the surf-riding threshold hypersurface is presented with successful examples. This
deals with all state and control variables in parallel, and excludes backward time integration and an orthogonal condition
in the iteration process. The bifurcation conditions identified were compared with the results from a direct numerical simulation
in the time domain. As a result, it was confirmed that the heteroclinic bifurcation provides a boundary between motions periodically
overtaken by waves and nonperiodic motions such as surf-riding and broaching. 相似文献
4.
随机风浪中舰船横摇倾覆概率分析 总被引:2,自引:0,他引:2
以路径积分法为基础,采用Gauss-Legendre公式探讨了随机风浪作用下舰船的运动及其倾覆概率计算。考虑阻尼力矩、复原力矩的非线性及风浪的随机性,建立了随机风浪中舰船运动的非线性微分方程,应用路径积分法给出白噪声随机扰动和定常风倾力矩作用时横摇角概率密度函数随时间的演变,按照现有的倾覆准则给出舰船倾覆概率的表达式。通过算例,验证了路径积分法的准确性,分析了各个参数对横摇角概率密度的影响,计算得出了不同风速、不同航速下的倾覆概率,以及倾覆概率随时间的变化。研究表明,此方法简便可行,并能在数量上预报舰船在随机风浪下的倾覆概率。 相似文献
5.
Nonlinear analysis of parametric rolling in longitudinal and quartering seas with realistic modeling of roll-restoring moment 总被引:4,自引:0,他引:4
Parametric rolling of a containership in longitudinal and quartering seas is examined by applying nonlinear dynamics to a 1DOF mathematical model with realistic modeling of the wave effect on roll-restoring moment. In our previous work, we confirmed that a mathematical model with a roll-restoring moment in waves calculated with the Froude–Krylov assumption could considerably overestimate the danger of capsizing associated with parametric rolling. Therefore, in the present work, all numerical calculations based on nonlinear analysis were carried out with the direct aid of a measured roll-restoring moment in waves. For this purpose, captive model experiments were conducted for various sets of wavelengths in longitudinal seas. This experiment demonstrates that the Froude–Krylov prediction could not explain the wavelength effect on restoring moment as the wave-steepness effect. Using the numerical model with the aid of this measured roll-restoring moment, the Poincaré mapping technique was applied to identify bifurcation structures of roll motions not only in longitudinal seas, but also in quartering seas. As a result, it was confirmed that capsizing associated with parametric rolling is more likely to occur in following seas than in quartering seas. However, period-doubling and chaos appeared in quartering seas. Finally, an averaging method assuming a period-2 orbit was applied to the same model with the same conditions as the Poincaré map. Reasonably good agreement was obtained between the numerical results with a Poincaré map and those with the averaging method in longitudinal seas, but the averaging method has limited capability in quartering seas. 相似文献
6.
K. J. Spyrou 《Journal of Marine Science and Technology》1995,1(1):24-36
The behavior of a ship encountering large regular waves from astern at low frequency is the object of investigation, with a parallel study of surf-riding and periodic motion paterns. First, the theoretical analysis of surf-riding is extended from purely following to quartering seas. Steady-state continuation is used to identify all possible surf-riding states for one wavelength. Examination of stability indicates the existence of stable and unstable states and predicts a new type of oscillatory surf-riding. Global analysis is also applied to determine the areas of state space which lead to surf-riding for a given ship and wave conditions. In the case of overtaking waves, the large rudder-yaw-surge oscillations of the vessel are examined, showing the mechanism and conditions responsible for loss of controllability at certain vessel headings.List of symbols
c
wave celerity (m/s)
-
C(p)
roll damping moment (Ntm)
-
g
acceleration of gravity (m/s2)
-
GM
metacentric height (m)
-
H
wave height (m)
-
I
x
,I
z
roll and yaw ship moments of inertia (kg m2)
-
k
wave number (m–1)
-
K
H
,K
W
,K
R
hull reaction, wave, rudder, and propeller
-
K
p
forces in the roll direction (Ntm)
-
m
ship mass (kg)
-
n
propeller rate of rotation (rpm)
-
N
H
,N
W
,N
R
hull reaction, wave, rudder, and propeller
-
N
P
moments in the yaw direction (Ntm)
-
p
roll angular velocity (rad/s)
-
r
rate-of-turn (rad/s)
-
R(,x)
restoring moment (Ntm)
-
Res(u)
ship resistance (Nt)
-
t
time (s)
-
u
surge velocity (m/s)
-
U
vessel speed (m/s)
-
v
sway velocity (m/s)
-
W
ship weight (Nt)
-
x
longitudinal position of the ship measured from the wave system (m)
-
x
G
,z
G
longitudinal and vertical center of gravity (m)
-
x
S
longitudinal position of a ship section (S), in the ship-fixed system (m)
-
X
H
,X
W
,X
R
hull reaction, wave, rudder, and propeller
-
X
P
forces in the surge direction (Nt)
-
y
transverse position of the ship, measured from the wave system (m)
-
Y
H
,Y
W
,Y
R
hull reaction, wave, rudder, and propeller
-
Y
p
forces in the sway direction (Nt)
-
z
Y
vertical position of the point of action of the lateral reaction force during turn (m)
-
z
W
vertical position of the point of action of the lateral wave force (m)
Greek symbols
angle of drift (rad)
-
rudder angle (rad)
-
wavelength (m)
-
position of the ship in the earth-fixed system (m)
-
water density (kg/m3)
-
angle of heel (rad)
-
heading angle (rad)
-
e
frequency of encounter (rad/s)
Hydrodynamic coefficients
K
roll added mass
-
N
v
,N
r
yaw acceleration coefficients
-
N
v
N
r
N
rr
N
rrv
,N
vvr
yaw velocity coefficients K. Spyrou: Ship behavior in quartering waves
-
X
u
surge acceleration coefficient
-
X
u
X
vr
surge velocity coefficients
-
Y
v
,Y
r
sway acceleration coefficients
-
Y
v
,Y
r
,Y
vv
,Y
rr
,Y
vr
sway velocity coefficients
European Union-nominated Fellow of the Science and Technology Agency of Japan, Visiting Researcher, National Research Institute of Fisheries Engineering of Japan 相似文献
7.
URANS analysis of a broaching event in irregular quartering seas 总被引:1,自引:0,他引:1
Pablo M. Carrica Kwang-Jun Paik Hamid S. Hosseini Frederick Stern 《Journal of Marine Science and Technology》2008,13(4):395-407
Ship motions in a high sea state can have adverse effects on controllability, cause loss of stability, and ultimately compromise
the survivability of the ship. In a broaching event, the ship losses control, naturally turning broadside to the waves, causing
a dangerous situation and possibly capsizing. Classical approaches to study broaching rely on costly experimental programs
and/or time-domain potential or system-based simulation codes. In this paper the ability of Reynolds averaged Navier–Stokes
(RANS) to simulate a broaching event in irregular waves is demonstrated, and the extensive information available is used to
analyze the broaching process. The demonstration nature of this paper is stressed, as opposed to a validated study. Unsteady
RANS (URANS) provides a model based on first principles to capture phenomena such as coupling between sway, yaw, and roll,
roll damping, effects of complex waves on righting arm, rudders partially out of the water, etc. The computational fluid dynamics
(CFD) method uses a single-phase level-set approach to model the free surface, and dynamic overset grids to resolve large-amplitude
motions. Before evaluating irregular seas two regular wave cases are demonstrated, one causing broaching and one causing stable
surf riding. A sea state 8 is imposed following an irregular Bretschneider spectrum, and an autopilot was implemented to control
heading and speed with two different gains for the heading controller. It is concluded that the autopilot causes the ship
to be in an adverse dynamic condition at the beginning of the broaching process, and thus is partially responsible for the
occurrence of the broaching event. 相似文献
8.
9.
Timothy Lilienthal Akihiko Matsuda Giles Thomas 《Journal of Marine Science and Technology》2007,12(2):111-118
This article presents work based on the development of a performance-based stability assessment method. It describes a numerical
method used to determine the survival limit for a dynamic intact stability assessment procedure. The numerical method utilises
a time-domain vessel motion program to assess the limit for a range of vertical centres of gravity (KG). The appropriateness
of the numerical predictions was examined through comparison with model experiment results. Free-running model tests were
conducted in regular following waves at discrete KGs. A comparison between the survival limits determined through the numerical
and experimental methods is presented. The current International Maritime Organisation (IMO) stability criteria are also evaluated
against the numerical and experimental dynamic performance-based stability assessment methods. 相似文献
10.
水下爆炸及随机外力下破损舰船的倾覆概率分析 总被引:1,自引:0,他引:1
探讨了水下爆炸载荷和随机风浪联合作用下破损舰船的运动及其倾覆概率的计算.将爆炸载荷作用及平均风扰动力矩处理为定常横倾力矩,建立了爆炸载荷和随机风浪中舰船运动的非线性微分方程.结合扩维技巧,将横摇方程转化为五维Ito随机微分方程,应用Gauss-Legendre路径积分法给出随机扰动为白噪声时横摇角度的概率密度函数随时间的演变,按照现有的倾覆准则给出预报一定装药量下舰船倾覆概率的表达式.通过算例,计算了破损舰船不同装药量下不同时刻的倾覆概率,分析不同装药量对倾覆概率的影响.研究表明,此方法简便可行,并能在数量上预报破损舰船在水下爆炸及随机风浪下的倾覆概率,为进一步研究舰船倾覆及稳性横准提供有益的参考. 相似文献
11.
船舶在随浪中的运动与横甩预报 总被引:2,自引:0,他引:2
本文在水平的随船坐标系下,建立了船舶在波浪中的六自由度操纵运动方程。进行船舶在波浪中的回转运动和Z形操纵运动模型试验,验证数学模型的正确性。通过不同波浪和航速条件下船舶Z形操纵运动的模拟计算,预报船舶在随浪中的横甩,预报结果与试验结果比较一致。 相似文献
12.
Parametrical studies based on numerical simulations were carried out for very steep regular waves to assess possible improvements
in the state-of-the art numerical modelling of the control and capsizing behaviour of ships in following and quartering seas.
A nonlinear 6-DOF numerical model has been developed with the inclusion of frequency-dependent terms, the so called memory
effects, and a flexible axis system that allows straightforward combination of seakeeping and manoeuvring models while accounting
for extreme motions. The previously undertaken validation analyses using extensive model test data provided qualitatively
good agreement, whereas the comparison with numerical models without coupling of the vertical motions and frequency-dependent
hydrodynamic terms embodied in radiation forces identified improvements in the accuracy. However, to broaden the assessment
of the numerical model, further parametrical numerical analyses were carried out using two ships, which had previously been
tested in the validation analyses, for various operational and environmental conditions. These parameters were changed in
accordance with the recommendations from international organisations and experience from model tests to realise and avoid
dangerous conditions that often result in capsizing, such as broaching associated with surf riding and low-cycle resonance.
As a result of the parametric analysis, we discuss the sensitivity of the improvements in the numerical model for various
critical operational and design parameters and its possible use to provide a link between the ship's behavior and these parameters. 相似文献
13.
Vertical bending moment (VBM) is of crucial importance in ensuring the survival of vessels in rough seas. With regard to conventional vessels, wave-induced maximum VBM is normally considered to be experienced in head seas. It is conservative to determine the extreme VBM based on either numerical simulations or model tests in long-crested head seas. Extensive model tests have been conducted in head seas with focus on the nonlinear vertical responses in severe seas, and the measured results were compared with numerical calculations for validation. Unexpected phenomena, however, were observed during the model tests of an ultra-large containership. The maximum sagging and hogging VBMs were encountered in oblique seas. Furthermore, the significant wave height used in oblique seas was even smaller than that used in head seas. The nonlinear vertical load effects in oblique seas require further investigations for this particular vessel. Limited experimental results in oblique seas have been reported, in which the lateral responses were always more concerned than the vertical responses. Up to now, rare systematic comparisons of the nonlinear vertical responses between head and oblique seas have been published, especially when the hydroelastic effects are also accounted for. A 13000-TEU ultra-large containership model, which was designed by Hyundai Heavy Industries (HHI), has been tested in the towing tank and the ocean basin at the Marintek center in Trondheim. The experimental results in regular waves are first compared between head and oblique seas. The statistical characteristics of the VBM amidships under nineteen irregular wave conditions are then investigated. Next, the extreme hogging and sagging VBMs are compared under different wave conditions with focus on the extreme hogging VBMs. At the end of the paper, the uncertainties in the experiments are discussed. 相似文献
14.
This paper aims to present and explain the work undertaken at the SSRC on the Safety of Bulk Carriers in extreme weather conditions over the past 3 years, to draw conclusions deriving there from, concerning key influencing design, operational and environmental parameters and to offer recommendations regarding the rule development process and on the way forward considering research, development and implementation to ship design and operation with the view to improving the safety of these ships cost-effectively. In severe storms, hatch covers of low freeboard vessels such as bulk carriers are the first-line of protection against flooding. Present methods of hatch covers design are still empirical because impact loads due to green seas and structural behaviour due to this type of loads have not been examined, hence not known accurately. The loading due to green seas is implicitly non-linear and, as model test results demonstrated, bulk carriers in extreme conditions are exposed to significant loads, which in some cases exceed current design standards. Since the consequences of hatch cover failure are potentially catastrophic, the risk of this happening should be quantified in probabilistic terms as required by modern safety standards. To this end, the paper aims to propose and implement a methodology for estimating probabilities of deck wetness and impact loads due to green seas as a function of key design and operational parameters. 相似文献
15.
Parametric rolling prediction in irregular seas using combination of deterministic ship dynamics and probabilistic wave theory 总被引:1,自引:0,他引:1
Atsuo Maki Naoya Umeda Shigeaki Shiotani Eiichi Kobayashi 《Journal of Marine Science and Technology》2011,16(3):294-310
In recent years there have been reports of serious accidents of parametric rolling for modern container ships and car carriers.
For avoiding such accidents, a prediction method of parametric rolling in irregular seas is required. Since parametric rolling
is practically non-ergodic, repetitions of numerical simulations or experiments could be not feasible to ascertain the behaviour.
Therefore, in this paper, a method combining a stochastic approach with a deterministic approach in order to estimate the
probabilistic index without such simple repetitions is developed. The ship's response in regular seas is estimated by solving
an averaged system of the original 1-DoF roll model, and random waves necessary for occurrence of parametric rolling is achieved
by using Longuet-Higgins’s or Kimura’s wave group theory. As a result, a fast and robust computation method of the probabilistic
index is established. Finally, it is concluded that the proposed method is considered to be one of the useful tools for discussing
the new IMO Intact Stability Code. 相似文献
16.
The probability of capsize of purse seiners in irregular beam seas and the effect of freeboard height and metacentric height
on trapped water on the deck was investigated. The aim was to quantify a safety level that can be achieved by direct stability
assessment for this type of fishing vessel. The amount of trapped water on deck was numerically estimated using a hydraulic
flow assumption. The long-term capsizing probabilities were estimated using a piecewise linear approach together with wave
statistics from major Japanese fishing areas. The estimated safety level of capsizing probability was compared with that obtained
by the IMO weather criterion and by the water-on-deck criterion of the IMO Torremolinos Convention. Numerical results for
four typical Japanese purse seiners indicated that the effect of freeboard, on the amount of trapped water on deck, is more
important than that of the metacentric height. Besides the metacentric height and the freeboard, it was shown that the danger
of capsizing is a function of the rise of floor. The safety level obtained by the capsizing probability approach is generally
higher than that based on the IMO weather criterion. However, the water-on-deck criterion provides a higher safety level than
the capsizing probability approach for ships with a low rise of floor. 相似文献
17.
本文采用半约束模型试验技术,对一条高速船在规则波中随浪和斜浪工况进行了流体动力系列试验,以探讨航运的安全性,验证作用于船体上波浪力的估算方法。对每次试验,以波动方程的形式采用数值估算方法确定环绕船模的波浪运动的时间历程。并用同样的方法从测量数据中提取垂荡和纵摇与模型测量运动,一阶波导纵荡、横荡作用力和首摇力矩。因此合理比较理论计算的波浪力与力矩的时间历程成为可能。这表明SSPA海事动力学的研究所(MDL)模型试验设施可以提供高质量的测量,与所述计算方法结合起来可用来验证理论计算和建立半经验方法。 相似文献
18.
19.
20.
Ingo Drummen Gaute Storhaug Torgeir Moan 《Journal of Marine Science and Technology》2008,13(4):428-445
Fatigue cracks have been known to occur in welded ships for several decades. For large ocean-going ships wave-induced vibrations
can, depending on trade and design, cause up to 50% of the fatigue damage. The vibrations may be due to springing and whipping
effects. In this paper, we address the fatigue damage caused by wave-induced vibrations in a containership of newer design
trading in the North Atlantic. The fatigue damage was obtained both experimentally and numerically. The experimental results
were found from tests performed with a flexible model of the ship, while the numerical predictions were done using nonlinear
hydroelastic strip theory. The measurements showed that the wave-induced vibrations contributed approximately 40% of the total
fatigue damage. The numerical method predicted the wave frequency damage well, but was found to overestimate the total fatigue
damage by 50%. This was mainly due to an overprediction of the wave-induced vibrations. The discrepancy is partly related
to three-dimensional (3D) effects which are not included in the two-dimensional (2D) slamming calculation, and partly to an
overprediction of the springing contribution. Moreover, the numerical method does not account for the steady wave due to forward
speed. By using a simplified approach we show that high-frequency damage can be significantly reduced by including the steady
wave for the relevant vessel, implying better agreement with the experimental results. 相似文献