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1.
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
2.
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
3.
Hiroshi Kagemoto 《Journal of Marine Science and Technology》2003,7(3):128-136
Explicit expressions are derived for the drift force that will act on a bottom-mounted, slightly porous vertical cylinder
fixed in regular waves. The drift-force expressions derived both from the near-field and the far-field are shown. It is indicated,
and numerically demonstrated, that the conventional far-field formula does not hold for a porous body, but needs the additional
term of a near-field body-surface integration.
Received: July 4, 2002 / Accepted: November 6, 2002
Acknowledgment. The author would like to acknowledge Prof. Kashiwagi, of Kyushu University, for indicating the work of Havelock relating
to Eq. 20.
Address correspondence to: H. Kagemoto (e-mail: kagemoto@k.u-tokyo.ac.jp) 相似文献
4.
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
5.
Masahiko Fujikubo Taoyun Xiao Kazuhiro Yamamura 《Journal of Marine Science and Technology》2003,7(3):119-127
A structural safety assessment of a pontoon-type very large floating structure (VLFS) surrounded by a gravity-type breakwater
was carried out for extreme wave conditions by considering the damage to the breakwater. Bending and shear collapses are considered
to be a failure mode of the floating structure, while overturning damages the breakwater. The probability of the breakwater
overturning, and the transmitted wave height before and after damage to the breakwater, are evaluated using design formulae
for port and harbor facilities in Japan. The ultimate bending and shear strengths of the floating structure are calculated
by the idealized structural unit method (ISUM) and FEM, respectively. The calculated failure probability for the floating
structure is compared with the specified target safety level. It was found that the floating structure under consideration
is most likely to fail by bending in transverse waves, and that the corresponding failure probability satisfies the target
level.
Received: September 12, 2002 / Accepted: October 4, 2002
Acknowledgment. The authors are grateful to Dr. Shigeo Ohmatsu, National Maritime Research Institute, Japan, for allowing us to use the program
of hydroelastic response analysis.
Address correspondence to: M. Fujikubo (e-mail: fujikubo@naoe.hiroshima-u.ac.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Arthit Jpn 2002;190:337–345) 相似文献
6.
Alexander B. Phillips Stephen R. Turnock Maaten Furlong 《Journal of Marine Science and Technology》2010,15(3):201-217
Manoeuvring underwater vehicles experience complex three-dimensional flow. Features include stagnation and boundary layer
separation along a convex surface. The resulting free vortex sheet rolls up to form a pair of streamwise body vortices. The
track and strength of the body vortex pair results in a nonlinear increase in lift as body incidence increases. Consequently,
accurate capture of the body vortex pair is essential if the flow field around a manoeuvring submarine and the resulting hydrodynamic
loading is to be correctly found. This work highlights the importance of both grid convergence and turbulence closure models
(TCMs) to the strength and path of the crossflow-induced body vortices experienced by the DOR submarine model at an incidence
angle of 15°. Five TCMs are considered; Spalart–Allmaras, k-ε, k-ω, shear stress transport, and the SSG Reynolds stress model. The SSG Reynolds stress model shows potential improvements in
predicting both the path and strength of the body vortex over standard one- and two-equation TCMs based on an eddy viscosity
approach. 相似文献
7.
A flow-simulation method was developed to predict the performance of a sailing boat in unsteady motion on a free surface.
The method is based on the time-marching, finite-volume method and the moving grid technique, including consideration of the
free surface and the deformation of the under-water shape of the boat due to its arbitrary motion. The equation of motion
with six degrees of freedom is solved by the use of the fluid-dynamic forces and moments obtained from the flow simulation.
The sailing conditions of the boat are virtually realized by combining the simulations of water-flow and the motion of the
boat. The availability is demonstrated by calculations of the steady advancing, rolling, and maneuvering motions of International
America's Cup Class (IACC) sailing boats.
Received: December 25, 2001 / Accepted: March 26, 2002 相似文献
8.
Anouck R. Girard Daniel M. Empey William C. Webster J. Karl Hedrick 《Journal of Marine Science and Technology》2003,7(3):109-118
The concept of a mobile offshore base (MOB) reflects the need to stage and support military and humanitarian operations anywhere
in the world. A MOB is a self-propelled, modular, floating platform that can be assembled into lengths of up to 2 km, as required,
to provide logistic support to US military operations where fixed bases are not available or adequate. It accommodates the
take-off and landing of C17 aircraft, and can be used for storage, as well as to send resources quickly to shore. In most
concepts, the structure is made of three to five modules, which have to perform long-term station-keeping in the presence
of winds, waves, and currents. This is usually referred to as dynamic positioning (DP). In the MOB, the alignment is maintained
through the use of thrusters, connectors, or a combination of both. In this paper, we consider the real-time control of scaled
models of a MOB. The modules are built at the 1 : 150 scale, and are kept aligned by rotating thrusters under a hierarchical
hybrid control scheme. This paper describes a physical testbed developed at the University of California, Berkeley, under
a grant from the US Office of Naval Research, for the purpose of evaluating competing MOB control concepts.
Received: June 4, 2002 / Accepted: October 30, 2002
Acknowledgments. This material is based on work supported by the MOB Program of the US Office of Naval Research under grant N00014-98-1-0744.
The authors would like to thank the Link Foundation for its support. Many thanks go to Stephen Spry for his experimental work.
The photographs are courtesy of Bill Stone, Gerald Stone, and Jay Sullivan of the PATH Publications staff.
Address correspondence to: A.R. Girard (e-mail: anouck@eecs.berkeley.edu) 相似文献
9.
Shogo Nakasumi Katsuyuki Suzuki Daiji Fujii Hideomi Ohtsubo 《Journal of Marine Science and Technology》2003,7(4):180-188
This article presents a mixed method of analyzing shell elements and solid elements using the overlaying mesh method. In
the structural design of a ship's hull, the shell elements are used for the global model. However, the solid elements are
necessary to analyze the stress concentration zones or the vicinity of a crack. In such cases, the models are analyzed using
zooming analysis, in which the results of a global model analysis are transferred to a local model analysis by imposing boundary
conditions. This method is more advantageous than zooming analysis in terms of the accuracy of the solution and the modeling
flexibility. Some examples of a plate model with a cracked surface or with a projection are shown in order to demonstrate
the effectiveness of the method.
Received: August 6, 2002 / Accepted: November 25, 2002
Address correspondence to: S. Nakasumi (sumi@nasl.t.u-tokyo.ac.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;189:219–224; and 190:655–662) 相似文献
10.
Satoru Shiraishi Kazuhiro Iijima Keitaro Harasaki 《Journal of Marine Science and Technology》2003,8(1):1-10
This article describes the results of hydraulic model tests of the elastic response of a very large floating structure (VLFS)
moored inside a reef in an isolated island. The distributions of strains and vertical displacements due to the elastic response
of the VLFS were measured. The response characteristics were strongly affected by deformed nonlinear waves inside the reef.
A two-step analytical method to compute the elastic response of a VLFS is proposed, and its validity is verified using the
results of the hydraulic model tests.
Received: May 2, 2002 / Accepted: March 17, 2003
RID="*"
ID="*" Address correspondence to: S. Shiraishi (shiraishi@pari.go.jp)
Acknowledgment. This study was supported by the Program for Promotions of Fundamental Transport Technology Research from the Corporation
for Advanced Transport and Technology (CATT). 相似文献
11.
Process planning for a hull structure defines the assembly sequence of the hull block. Although this activity is very important
because the working strategy defines the production costs, to date it has been done manually. To raise the efficiency of this
process, we developed a practical computer-aided process planning system. It has been developed using deliverables obtained
from advanced computer integrated manufacturing system (CIM; ACIM) for shipbuilding projects sponsored by the Ship and Ocean
Foundation (SOF). The system has a knowledge base which contains the know-how of skilled designers as well as design practices,
and allows the assembly sequence of hull parts and intermediate products to be defined automatically. The system has been
integrated with the shipyard CAD system MATES, and put to practical use.
Received: August 19, 2002 / Accepted: November 25, 2002
Address correspondence to: Y. Sasaki (yuuichi_sasaki@mhi.co.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;189:309–315) 相似文献
12.
Yusuke Yano Shinichi Takagawa Kazuyasu Wada 《Journal of Marine Science and Technology》2003,7(3):101-108
The Japan Marine Science and Technology Center (JAMSTEC) has been, and is now promoting the “OD21” program (i.e., “Ocean
drilling in the 21st century”). This is the first plan in the world to utilize deep-water riser-drilling technologies for
scientific drilling. One of the important factors for the success of this program is the development of a high-performance
drilling vessel. Since 1990, JAMSTEC has been continuing a technological study of a riser-drilling vessel for scientific studies
with an operational capability in waters up to 4000 m deep. It was decided to start the construction with a two-phase plan:
a vessel with a riser operation for waters up to 2500 m deep will be constructed in the initial stage, and then the vessel
will be modified to a 4000-m depth capability. In the development process of the vessel, named Chikyu, many new technical developments have taken place, such as drilling/coring equipment, a dynamic positioning system, etc.
Thus, the Chikyu is expected to contribute to ocean engineering and other work, in addition to scientific advances.
Received: June 15, 2002 / Accepted: November 11, 2002
Address correspondence to: Y. Yano (e-mail: yanoy@jamstec.go.jp) 相似文献
13.
Tomohiro Takai Manivannan Kandasamy Frederick Stern 《Journal of Marine Science and Technology》2011,16(4):434-447
The accurate prediction of waterjet propulsion using computational fluid dynamics (CFD) is of interest for performance analyses
of existing waterjet designs as well as for improvement and design optimization of new waterjet propulsion systems for high-speed
marine vehicles. The present work is performed for three main purposes: (1) to investigate the capability of a URANS flow
solver, CFDSHIP-IOWA, for the accurate simulation of waterjet propelled ships, including waterjet–hull interactions; (2) to
carry out detailed verification and validation (V&V) analysis; and (3) to identify optimization opportunities for intake duct
shape design. A concentrated effort is applied to V&V work and performance analysis of waterjet propelled simulations which
form the focus of this paper. The joint high speed sealift design (JHSS), which is a design concept for very large high-speed
ships operating at transit speeds of at least 36 knots using four axial flow waterjets, is selected as the initial geometry
for the current work and subsequent optimization study. For self-propelled simulations, the ship accelerates until the resistance
equals the prescribed thrust and added tow force, and converges to the self propulsion point (SPP). Quantitative V&V studies
are performed on both barehull and waterjet appended designs, with corresponding experimental fluid dynamics (EFD) data from
1/34 scale model testing. Uncertainty assessments are performed on iterative convergence and grid size. As a result, the total
resistance coefficient for the barehull case and SPP for the waterjet propelled case are validated at the average uncertainty
intervals of 7.0 and 1.1%D, respectively. Predictions of CFD computations capture the general trend of resistance over the speed range of 18–42 knots,
and show reasonable agreement with EFD with average errors of 1.8 and 8.0%D for the barehull and waterjet cases, respectively. Furthermore, results show that URANS is able to accurately predict the
major propulsion related features such as volume flow rate, inlet wake fraction, and net jet thrust with an accuracy of ~9%D. The flow feature details inside the duct and interference of the exit jets are qualitatively well-predicted as well. It
is found that there are significant losses in inlet efficiency over the speed range; hence, one objective for subsequent optimization
studies could be maximizing the inlet efficiency. Overall, the V&V work indicates that the present approach is an efficient
tool for predicting the performance of waterjet propelled JHSS ships and paves the way for future optimization work. The main
objective of the optimization will be reduction of powering requirements by increasing the inlet efficiency through modification
of intake duct shape. 相似文献
14.
Yoshitaka Ogawa 《Journal of Marine Science and Technology》2003,7(3):137-144
To develop a practical prediction method for the green water load and volume on the bow deck in irregular waves, model tests
were conducted using a tanker and a cargo ship on a domestic Japanese voyage. The relation between green water load and relative
water height at the stem was considered. Based on the finding that the maximum value of the green water load is proportional
to the square of the maximum value of the water elevation over the bow top, the probability density functions of the green
water load and volume in short-term predictions were proposed. It was verified that the proposed functions show good agreement
with the measured distributions, especially in the tails, and were better than conventional functions. Using these functions,
long-term predictions of the green water load were carried out. It was confirmed that the present method is more rational
than the conventional one for estimating the long-term probability of the green water load. An assessment of the bow height
of a domestic Japanese ship from the viewpoint of deck wetness was carried out using these prediction methods. This research
was used as the technical background for the revision of domestic rules on load lines, which was enforced in October 2001.
Received: July 19, 2002 / Accepted: October 30, 2002
Acknowledgment. Some of the present study was carried out as part of a cooperation project (RR45) with the Shipbuilding Research Association
of Japan, supported by the Nippon Foundation.
Address correspondence to: Y. Ogawa (e-mail: ogawa@nmri.go.jp) 相似文献
15.
Hiroaki Takamura Koichi Masuda Hisaaki Maeda Masatoshi Bessho 《Journal of Marine Science and Technology》2003,7(4):164-174
Seaquakes, which are characterized by the propagation of vertical earthquake motion at the sea bottom as a compression (longitudinal)
wave, are reported to cause damage to ships, and their effect on floating structures is a matter of great concern. To comprehend
the basic properties of seaquakes, we first discuss a method to calculate the displacement of the seabed when it is subjected
to hydrodynamic pressure. To investigate the interrelationship between the vibration of a floating structure and the deformation
of the seabed, a new boundary integral equation is derived which assumes that the seabed is a semiinfinite homogeneous elastic
solid in order to analyze the seaquake-induced hydrodynamic pressure acting on the floating structure. By considering the
propagation of the seismic wave in the ground and in the water, the incident wave potential in seaquake problems is also deduced
and its characteristics are discussed. Finally, the response of a very large floating structure in a seaquake is investigated
using a fluid force analysis method, and considering the interrelationship between the vibration of the floating structure
and the deformation of the seabed.
Received: August 19, 2002 / Accepted: November 11, 2002
Address correspondence to: H. Takamura (hiroaki_takamura@nishimatsu.co.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;189:87–92,93–100 and 190:381–386) 相似文献
16.
Naoya Umeda Hirotada Hashimoto Akihiko Matsuda 《Journal of Marine Science and Technology》2003,7(3):145-155
We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following
and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring
coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass
due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated
by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed
reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring
forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and
the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the
lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried
out with these second-order terms of waves, and the results were compared with the results of free-running model experiments.
An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries
of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves
are not so crucial for predicting the capsizing boundaries themselves.
Received: June 20, 2002 / Accepted: October 10, 2002
Acknowledgments. This research was supported by a Grant-in-Aid for Scientific Research of the Ministry of Education, Culture, Sports, Science
and Technology of Japan (No. 13555270). The authors thank Prof. N. Rakhmanin of the Krylov Ship Research Institute for providing
the Russian literature, as well as Mr. H. Murata of NHK (Japan Broadcasting Corporation) for translating it into Japanese.
Address correspondence to: N. Umeda (e-mail: umeda@naoe.eng.osaka-u.ac.jp) 相似文献
17.
Antonio Pinto-Heredero Tao Xing Frederick Stern 《Journal of Marine Science and Technology》2010,15(4):295-315
Vortical structures and associated instabilities for flows around the Wigley hull for a wide range of drift angles (10° ≤ α ≤ 60°) with free surface are identified and analyzed. Quantitative verification and validation are conducted on three systematically
refined grids with comparison to the experimental data for α = 10°. Analysis of the flow pattern shows a strong correlation between the vortical structures and free-surface wave elevation.
For α = 10° and 30°, the flows remain steady and vortices are generated at the keel and fore and aft perpendiculars of the hull.
The strength and complexity of these vortices increase with increasing α. At α = 45°, flow becomes unsteady without any significant change in the main flow pattern. At α = 60°, a complex and unsteady flow field on the leeward side of the hull is formed with a large recirculation region from
the aft to the fore end, which prevents the flow coming from below the keel from moving up and generating the keel vortices
observed at lower drift angles. Karman-like and helical instabilities are analyzed. The effect of Froude number is more apparent
for large than for small drift angles. 相似文献
18.
Naoki Osawa Yasumitsu Tomita Kiyoshi Hashimoto 《Journal of Marine Science and Technology》2003,7(4):189-204
In order to accumulate knowledge about how material compositions and manufacturing methods affect fatigue strength, this
paper investigates the relationship between the swiftness of the changes in the macroscopic indices of the crack initiation
process and the hardening properties of a material. This is done by calculating the cyclic deformation behavior of a f.c.c.
single crystal. The relationship between the swiftness of the changes and the crystal geometries is also examined by calculating
the deformation behavior of a f.c.c. crystal with a high Schmid factor buried in a large crystal with a low Schmid factor.
In addition, a multiscale hardening rule based on forest theory is developed in order to examine the microscopic mechanisms
of fatigue slip band (persistent slip bands, PSBs) formation. The validity of the theories presented is examined by comparing
the changing nature of the measured and calculated hysteresis loop shapes of f.c.c. single crystals. Inhomogenous slip deformation
through the crystal is also investigated, and inferences are then drawn about the microscopic mechanisms of cyclic hardening
and PSB formation.
Received: August 5, 2002 / Accepted: December 18, 2002
Address correspondence to: N. Osawa (osawa@naoe.eng.osaka-u.ac.jp)
Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 1998;184:351–363, 1999;185:283–292
and 186:535–544, 2001;190:539–551) 相似文献
19.
带流水孔潜体流场数值模拟 总被引:10,自引:1,他引:9
本文通过求解RANS方程,结合PISO算法与k-ω湍流模型,数值模拟了带有两种不同形式流水孔(纵缝式与格栅式)潜体的内外流场.数值模拟给出了流水孔流场的精细结构,计算并分析了潜体各个壁面上阻力成分的大小与成因.计算得到的流水孔阻力增量与试验值吻合较好.对计算结果的分析表明:流水孔引起的阻力增量主要集中在导流板与流水孔壁上;内部空腔壁上的阻力值是可以忽略的小量;涡旋流动主要集中在导流板之间;流水孔阻力系数随雷诺数的增加而趋于一稳定值.计算结果表明,本文中使用的方法可用于模拟流水孔内外流场. 相似文献
20.
Based on a volume of fluid two-phase model imbedded in the general computational fluid dynamics code FLUENT6.3.26, the viscous flow with free surface around a model-scaled KRISO container ship (KCS) was first numerically simulated. Then with a rigid-lid-free-surface method, the underwater flow field was computed based on the mixture multiphase model to simulate the bubbly wake around the KCS hull. The realizable k-ε two-equation turbulence model and Reynolds stress model were used to analyze the effects of turbulence model on the ship bubbly wake. The air entrainment model, which is relative to the normal velocity gradient of the free surface, and the solving method were verified by the qualitatively reasonable computed results. 相似文献