共查询到20条相似文献,搜索用时 530 毫秒
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本文采用网格节点型有限体积法求解二维瞬态雷诺方程,采用矢量化方法离散雷诺方程,从而构建并得到新的数值模型,该模型既有有限体积法守恒性的特点,又能适用于结构复杂的求解域.通过与相关算例的对比验证,证明了该模型可适用于滑动轴承润滑特性的研究,同时精度也可以得到保证;根据计算得到的压力分布特点,采用不同的网格类型和网格数量重新划分求解域,并对计算结果和时间进行了对比,结果表明可以采用不同的稀疏网格来提高计算效率;通过计算圆锥形织构轴承的压力分布,证实了该模型对复杂求解域的良好适用性. 相似文献
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Use of 3D compartment model for simplified full ship FE model. Part I: construction of FE model 总被引:1,自引:1,他引:0
Beom-Seon Jang Jae-Hoon Jung Yong-Suk Suh 《Journal of Marine Science and Technology》2008,13(2):154-163
Classification societies cannot cover the torsional strength assessment with simple empirical formula as the size of a containership
increases drastically over 10 000 TEU in recent years. Torsional strength of a container ship is very difficult to estimate
with an analytical method due to its alternatively varying cross sections, i. e. an open and a closed section. This article
proposes an approach to construct a simplified FE model using a 3D compartment model available from the beginning of ship
design process. The model is cut to pieces of lots of small pieces of lines by a set of transverse, longitudinal and horizontal
planes. Two algorithms are developed for mesh generation of internal structures; one for assembling the broken lines into
closed loops and the other for automatically generating mesh from the loops. Another algorithm is proposed to generate mesh
for outer hull using outermost nodes of the FE model built for internal members. The validity of the simplified model is discussed
along with a beam theory based approach in J Mar Sci Technol (2008) 相似文献
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《Journal of Marine Systems》2005,53(1-4):1-17
Constructing models from time series with nontrivial dynamics is a difficult problem. The classical approach is to build a model from first principles and use it to forecast on the basis of the initial conditions. Unfortunately, this is not always possible. For example, in fluid dynamics, a perfect model in the form of the Navier–Stokes equations exists, but initial conditions and accurate forcing terms are difficult to obtain. In other cases, a good model may not exist. In either case, alternative approaches should be examined. This paper describes an alternative approach of combining observations and numerical model results in order to produce an accurate forecast. The approach is based on application of a method inspired by chaos theory for building nonlinear models from data called Local Models. Embedding theorem based on the time lagged embedded vectors is the basis for the local model. This technique is used for analysis and updating of numerical model output variables to forecast and correct the errors created by numerical model. The local model approximation is a powerful tool in the forecasting of chaotic time series and has been employed for wave prediction in a forecasting horizon from a few hours to 24 h. The efficacy of the local model as an error correction tool (by combining the model predictions with the observations) compared with the predictions of linear auto regressive models has been brought up. In the present study, the parameters driving the local model are optimized using evolutionary algorithms. 相似文献
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Wave-induced vessel motion prediction plays a critical role in ensuring safe marine operations. The operational limiting criteria can usually be calculated by applying presumed linearized vessel motion transfer functions based on the specified vessel loading condition, which may deviate from the real vessel condition when the operation is executed. Reducing the uncertainties of the onboard vessel loading condition can therefore improve the accuracy of vessel motion prediction and hence improve the safety and cost-efficiency for marine operations. However, parameters related to the onboard vessel loading condition can be difficult to measure directly, such as the center of gravity and moments of inertia. In addition, the hydrodynamic viscous damping terms are always subject to significant uncertainties and sometimes become critical for accurate vessel motion predictions. A very promising algorithm for the tuning of these important uncertain vessel parameters based on the unscented Kalman filter (UKF) that uses onboard vessel motion measurements and synchronous wave information was proposed and demonstrated previously by application to synthetic data. The present paper validates the UKF-based vessel seakeeping model tuning algorithm by considering measurements from model-scale seakeeping tests. Validation analyses demonstrate rational tuning results. The observed random errors and bias in relation to the measurement functions due to the applied simplification and linearization in the seakeeping simulations can lead to biased tuning. The importance of designing the state space and the measurement space is demonstrated by case studies. Due to the nonlinear relationship between the uncertain vessel parameters and the vessel motions, the tuning is shown to be sensitive to the mean state vector and selection of the surrounding sigma points. 相似文献
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Beom-Seon Jang Jae-Hoon Jung Yong-Suk Suh 《Journal of Marine Science and Technology》2008,13(4):408-415
This is Part II in a series of papers. Part I (J Mar Sci Technol 13:154–163) deals with an approach employed to construct
a simplified FE model using a 3D compartment model available from the beginning of the ship design process. This paper begins
by describing the limitations of an analytical approach based on shear warping beam theory for assessing torsional strength.
Next, the structural parts of a container ship that have a negligible effect on hull girder bending strength and torsional
strength are determined. This is verified by removing these parts from a conventional FE model and comparing the results obtained
using this modified model with those yielded by the original model. The fore end part, the aft end part and the deck house
are examined. Since these parts have complicated structures and relevant drawings for them are issued later than cargo structure
drawings, modeling them exactly can result in a delay in the completion of the full ship FE model. This paper also verifies
the validity of the simplified FE model built by applying the method proposed in Part I and comparing the results obtained
with it with those given by a conventional full ship FE model. The stresses on hatch coaming top, the maximum diagonal elongations
of the hatch coaming, and the maximum hatch corner movements are evaluated to check the validity of the simplified model. 相似文献