排序方式: 共有1868条查询结果,搜索用时 15 毫秒
851.
Alban Leroyer Sophie Barré Jean-Michel Kobus Michel Visonneau 《Journal of Marine Science and Technology》2008,13(1):1-15
This article aims at verifying the capabilities of a Reynolds-Averaged Navier-Stokes Equations (RANSE) solver (ISIS-CFD, developed
at the Fluid Mechanics Laboratory of Ecole Centrale de Nantes [LMF]) to accurately compute the flow around an oar blade and
to deduce the forces on it and other quantities such as efficiency. This solver is structurally capable of computing the flow
around any blade shape for any movement in six degrees of freedom, both when the blade pierces the free surface of the water
and when it does not. To attempt a first validation, a computation was performed for a simplified case chosen among those
for which experimental results are available at LMF. If results prove satisfactory for a simplified blade shape and for a
movement that respects the main characteristics of blade kinematics, then the solver could be used for real oars and more
realistic kinematics. First, the experimental setup is considered, and the objectives, methodologies, and procedures are elucidated.
The choice of the test case for numerical validation is explained, i.e., a plane rectangular blade with a constant immersion
and a specified movement deduced from analogy with tests on propellers. Next, the numerical framework is presented and the
Navier-Stokes solver and methods for handling multifluid flows and moving bodies are described. Lastly, numerical results
are compared with experimental data, highlighting an encouraging agreement and proving the relevance and the complementarity
of both approaches. 相似文献
852.
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
853.
This paper explores critical success conditions of collaborative planning projects in the area of urban transport, evaluating
the impact of new collaborative methods, instruments and processes on project performance. Hypothesis building is based on
a comparative, empirical research design, rather than on deductive theory construction. Potential critical success conditions
are derived from literature. Based on five urban transport planning projects in Gothenburg (Sweden), London (United Kingdom),
Milwaukee (United States), Tokyo (Japan) and Mexico City (Mexico), a rough set analysis of the five cases reveals validated
success conditions, which can be used for formulating hypotheses for further research or for policy and process improvement.
The results suggest that a dedicated management of the multi-actor network, a high diversity of actors, as well as an extensive
use of knowledge integration methods in combination with a high network density are critical success conditions of these planning
processes. Surprisingly, the extensive use of unilateral methods also showed to be an important success condition. The traditional
role of the planner will have to be complemented with the expertise of network and methodology management. The authors conclude
that rough set analysis can be a valuable addition to narrative, single-case analysis of collaborative urban transport planning
processes. 相似文献
854.
The paper presents a study on the incorporated probability that a tanker fleet meets a given permissible value of hull girder
strength loss. The analysis was based on a database of hull girder section modulus (HGSM) for as-gauged girth belts of tankers.
It was found that its mean value is below 5% over the entire life span of the analyzed tanker fleet. The Weibull probabilistic
distribution was found to best represent the time-varying HGSM loss. A method was developed for calculating the incorporated
safety of a fleet. As an example, the IMO requirement for a maximum HGSM reduction of 10% relative to its required value was
analyzed, accounting for time-variant HGSM loss and including a probabilistic model for coating longevity.
The views expressed in the paper are those of the authors and not necessary those of ABS. 相似文献
855.
LI Tie-shan YAN Shu-jia QIAO Wen-ming 《船舶与海洋工程学报》2007,6(4):1-7
This paper focuses on the problem of linear track keeping for marine surface vessels. The influence exerted by sea currents on the kinematic equation of ships is considered first. The input-to-state stability (ISS) theory used to verify the system is input-to-state stable. Combining the Nussbaum gain with backstepping techniques, a robust adaptive fuzzy algorithm is presented by employing fuzzy systems as an approximator for unknown nonlinearities in the system. It is proved that the proposed algorithm that guarantees all signals in the closed-loop system are ultimately bounded. Consequently, a ship's linear track-keeping control can be implemented. Simulation results using Dalian Maritime University's ocean-going training ship 'YULONG' are presented to validate the effectiveness of the proposed algorithm. 相似文献
856.
Qin Xia Jianli Duan Feng Gao Qiuxia Hu Yingdong He 《International Journal of Automotive Technology》2018,19(4):751-758
Intelligent vehicle greatly benefits traffic safety, efficiency and driving comfortable. With the development of intelligent driving technology and its application, it is becoming increasingly important to do effective and comprehensive tests before putting on the market. Comprehensively considering the cost of test, an automatic generation method of test scenarios is proposed to ensure both coverage and effectiveness. Based on the analyzed key infuence factors of an intelligent driving system, the analytic hierarchy process (AHP) is used to determine their importance and accordingly an complex index is defined, based on which an improved test case generation algorithm based on the pairwise independent combinatorial testing tool (PICT) is proposed to ensuring both combinational coverage and complexity of test cases. Finally, the test scenario is generated by clustering these discrete test cases considering similarity and complexity. The high complex test cases are preferred to be combined together and conducted preferentially to increase the test efficiency. The effectiveness of this method is validated by applying it on a lane departure warning system (LDW). 相似文献
857.
858.
Bo Leng Lu Xiong Zhuoping Yu Tong Zou 《International Journal of Automotive Technology》2018,19(1):55-62
For a distributed drive electric vehicle (DDEV) which is equipped with redundant actuators, allocation control is a key technique. Three different allocation control algorithms are designated with fixed efficiency matrix, dynamic efficiency matrix, and direct yaw moment distribution, respectively. All these algorithms are applied in a vehicle stability control system with hierarchical control structure and evaluated from three aspects, namely, control precision, real-time characteristics, and control energy. Comparison results demonstrate that the algorithm with dynamic efficiency matrix has the best comprehensive performance, which is also validated in field tests based on a DDEV equipped with four motors. 相似文献
859.
William Ritchie 《WMU Journal of Maritime Affairs》2004,3(2):193-204
The impact on the marine environment of the operation of the Sullom Voe Oil Terminal and its major port facility in the Shetland
Islands has been monitored continuously for more than twenty-five years. The site of this very large terminal straddles a
peninsula and the separation of the impact of the port on the sheltered west side (Sullom Voe) and the aqueous discharge from
the terminal to the east, into the strong tidal current of Yell Sound, has proven to be advantageous. There are two types
of monitoring, statutory (to comply with relevant legislation) and voluntary (to establish good practice and to examine a
wider range of impacts e.g. island-wide ornithology). The latter function is undertaken by an independent advisory committee
(SOTEAG). Over time, the nature and amount of voluntary monitoring has decreased in response to the long term evidence that
both terminal and port operations are having little or no impact on a wide range of habitats and species. Voluntary monitoring
also acts as an independent check on both compliance and other forms of environmental assessment. Although the terminal is
now operating at less than half its peak capacity, this does not mean that there has been apro-rata decrease in monitoring
activity. 相似文献
860.
SUNLi-cheng YANChang-qi SUNZhong-ning ZHANGQing-hua 《船舶与海洋工程学报》2003,2(1):41-44
Considering the special resistance characteristics of fluids flowing through ducts with small gaps, experiments are per-formed to investigate the resistance characteristics of single-phase water, which is forced to flow through vertical annuli. The gap sizes are 0.9, 1,4 and 2.4ram, respectively. The experiments are conducted under condition of 1 atm. The water in the annuli is heated by high temperature water reversely flowing through the inner tube and the outer annulus. The results show that the flow pattern begin to change from laminar to turbulent before Reynolds number approaches 2000, the flow resistance in annulus has llttie relations with the temperature difference and ways of being heated, but mainly depends on the ratio of mass flux to the width of annulus. 相似文献