Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration

Shanghai, China

Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration

Shanghai, China
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Wang Y.,Shanghai JiaoTong University | Wang Y.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Ocean Engineering | Year: 2017

This paper concerns the calculation of the short term extreme structural responses of a Spar-type floating wind turbine by applying the peak-over-threshold (POT) method. A new approach is proposed for finding an optimum threshold value by incorporating a declustering algorithm into the POT method. To select the clusters and check the Poisson character of the number of clusters we use the concept of a dispersion index. Then, the method of maximum product of spacing is utilized to estimate the parameters in the Generalized Pareto distribution of the largest values in all the selected clusters over the optimum threshold value. As examples of calculations, optimum threshold values of the out-of-plane and in-plane blade root bending moments and the tower – Spar interface bending moments of the NREL 5-MW OC3-Hywind floating wind turbine have been obtained by utilizing the new approach. The extreme response probability plot based on an optimum threshold value has been compared with the probability plot based on an empirical threshold value, and the accuracy and efficiency of the new approach have been convincingly validated. Goodness-of-fits plots have also been included in this article for testing the accuracy of the proposed new approach. Finally, in order to make a fair comparison, we have also extrapolated the short-term extreme values using the different POT methods and compared them with the reference values obtained directly from a large number of time-domain simulations. © 2017 Elsevier Ltd

Wang Y.,Shanghai JiaoTong University | Wang Y.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Wang L.,Shanghai Maritime University
Renewable Energy | Year: 2017

In this paper, the performances of a floating wind energy converter (the National Renewable Energy Laboratory 5 MW wind turbine installed on the ITI energy barge) in a realistic, multi-directional random sea are rigorously investigated. The wind loads acting on the floating wind energy converter are also fully considered in the numerical simulation process. Meanwhile, in order to improve the simulation efficiency, a new state space model (the FDI-SS model) is utilized to approximate the convolution integral term when solving the motion equation of the floating wind energy converter. For comparison purpose, the simulation results when the convolution integral term in the motion equation is approximated by a commonly used state space model based on the time domain (TD) realization theory are also included. The simulation results in this paper are systematically analyzed and compared, and the accuracy and efficiency of the new FDI-SS model are verified. Moreover, the simulation results in this article demonstrate the great necessity of using a realistic, multi-directional random sea state when calculating the generated electrical power and the dynamic responses of a floating wind energy converter. © 2016 Elsevier Ltd

Wang Y.-G.,Shanghai JiaoTong University | Wang Y.-G.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
China Ocean Engineering | Year: 2017

This article proposes a new methodology to predict the wave height and period joint distributions by utilizing a transformed linear simulation method. The proposed transformed linear simulation method is based on a Hermite transformation model where the transformation is chosen to be a monotonic cubic polynomial, calibrated such that the first four moments of the transformed model match the moments of the true process. The proposed new approach is applied for calculating the wave height and period joint distributions of a sea state with the surface elevation data measured at an offshore site, and its accuracy and efficiency are favorably validated by using comparisons with the results from an empirical joint distribution model, from a linear simulation model and from a second-order nonlinear simulation model. © 2017, Chinese Ocean Engineering Society and Springer-Verlag GmbH Germany.

Wang H.,Shanghai JiaoTong University | Chen K.,Shanghai JiaoTong University | You Y.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Physics of Fluids | Year: 2017

Experiments are performed for the characteristics of internal waves generated by four horizontally towed models, including a sphere and three slender models with different aspect ratios in a density stratified fluid with a strong halocline. The Reynolds number ranges within 3500 < Re = UD/ν < 126 000, and the Froude number ranges within 0.4 < Fr =U/N maxD < 18. Based on the time histories of the density perturbation and analysis of the correlation velocity of internal waves generated by the towed models, it is shown that the body-generated waves are stationary multiple-mode Lee waves, while the wake-generated waves are non-stationary wake waves mainly produced by the large-scale coherent structure in turbulent wakes acting as a moving excitation source. The transition between body-generated and wake-generated internal waves occurs at a critical Froude number Frc which is linearly dependent on the model aspect ratio. Before the transition, when the wave height H changes with the variation of Fr, a peak value of H can be observed and its corresponding Froude number Frp increases linearly with growing aspect ratio. After the transition, the Froude number Friw associated with the internal wave correlation velocity fluctuates within a certain range. The wave height linearly increases with increasing Fr regardless of the aspect ratios, and the wave pattern is dominated by a non-stationary wake-generated wave. According to the experimental configuration, a theoretical model is proposed to simulate the body-generated and wake-generated internal waves. The numerical results obtained by this theoretical model show general agreement with the experiments. Published by AIP Publishing.

Guo J.,Shanghai Maritime University | Zhou D.,Shanghai JiaoTong University | Zhou D.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Engineering Structures | Year: 2016

This paper proposes a new pretension simulation algorithm and examines the pretension feasibility for a new type of cable dome: a negative Gaussian curvature cable dome. First, the paper gives a pretension simulation algorithm based on the fuzzy relationship between the prestress and internal force. Second, a negative Gaussian curvature cable dome is proposed and the corresponding experimental model is designed and pretensioned according to the simulation results from the proposed simulation algorithm. The results indicate that the pretension simulation algorithm is efficient and accurate for simulating the pretension process and guiding the practical pretension. And the results also confirm that the negative Gaussian curvature cable dome can be pretensioned successfully, thus it can be constructed as a new type of cable dome. © 2016 Elsevier Ltd

Zhuang X.,Shanghai JiaoTong University | Zhuang X.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Shen J.,Fudan University
Medical Image Analysis | Year: 2016

A whole heart segmentation (WHS) method is presented for cardiac MRI. This segmentation method employs multi-modality atlases from MRI and CT and adopts a new label fusion algorithm which is based on the proposed multi-scale patch (MSP) strategy and a new global atlas ranking scheme. MSP, developed from the scale-space theory, uses the information of multi-scale images and provides different levels of the structural information of images for multi-level local atlas ranking. Both the local and global atlas ranking steps use the information theoretic measures to compute the similarity between the target image and the atlases from multiple modalities. The proposed segmentation scheme was evaluated on a set of data involving 20 cardiac MRI and 20 CT images. Our proposed algorithm demonstrated a promising performance, yielding a mean WHS Dice score of 0.899 ± 0.0340, Jaccard index of 0.818 ± 0.0549, and surface distance error of 1.09 ± 1.11 mm for the 20 MRI data. The average runtime for the proposed label fusion was 12.58 min. © 2016 Elsevier B.V.

Li Q.,Shanghai JiaoTong University | He G.,Shanghai JiaoTong University | He G.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Materials and Design | Year: 2016

Porous titanium with entangled wire structure was enhanced by filling gelatin into the porous structure to form a titanium-gelatin (Ti-G) composite. The density of the composites was 1.6-2.5 g/cm3, similar to that of bone. The strength and elastic modulus of the composites reached 12.9-39.4 MPa and 2.5-7.4 GPa, respectively, which were comparable to that of the cortical bone. Gelatin in Ti-G composite acted as the carrier of gentamicin sulphate (GS). Antibacterial efficacy of GS-loaded Ti-G against Staphylococcus aureus strain was tested. The lack of growth of Staphylococcus aureus strains was found in Luria-Bertani (LB) medium containing GS-loaded Ti-G. GS release behavior from the GS-loaded Ti-G composites in phosphate buffer saline (PBS) was investigated. The effective GS release times from Ti30-G and Ti50-G were 120 h and 168 h, respectively. The gelatin in Ti-G was just degraded 3.2% at the immersion time of 168 h and 9.0% at 336 h. The degradation rate of gelatin was much slower than release rate of GS, indicated that the GS release from gelatin was less affected by the gelatin degradation. These Ti-G composites loaded with drug(s) are expected to be good candidates as functional bone repair materials with drug-delivery capabilities. © 2016.Elsevier Ltd. All rights reserved.

Hu Z.,Shanghai JiaoTong University | Hu Z.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Tang W.,Shanghai JiaoTong University | Tang W.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | And 3 more authors.
Computer Methods in Applied Mechanics and Engineering | Year: 2016

A SIMPLE-based implicit method (SBMIM) for the strong coupling of fluid and structure is proposed. The SBMIM solves the Navier-Stokes (NS) equations of fluid by using a modified SIMPLE algorithm, which takes into account the structure governing equation. The free surfaces are reconstructed using the volume of fluid method (VOF), and the structure equation, embedded into the fluid solver, is processed with the widely used finite element method (FEM). We validate SBMIM by performing numerical simulations of a dam-breaking issue, a tank sloshing problem, and the free oscillation of a wash bulkhead in a liquid tank, and making comparisons against experimental measurements, theoretical results as well as other numerical solutions. The SBMIM is proved to be stable and robust under extreme simulation circumstances, and is applied to the strong coupling of wave impact on deck structure. © 2015 Elsevier B.V.

Wang Y.,Shanghai JiaoTong University | Wang Y.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Applied Ocean Research | Year: 2016

This article concerns the calculation of nonlinear crest distribution for shallow water Stokes waves. The calculations have been carried out by incorporating a second order nonlinear wave model into an asymptotic analysis method. This is a new approach to the calculation of wave crest distribution, and, as all of the calculations are performed in the probability domain, avoids the need for long time-domain simulations. The accuracy and efficiency of this new approach for calculating the wave crest distribution are validated by comparing the results predicted using it with those predicted by using the Monte Carlo simulation (MCS) method, by using a previous Transformed Rayleigh method, by using some existing wave crest distribution formulas, and by using the measured surface elevation data at the Poseidon platform in the Japan Sea. © 2016 Elsevier Ltd.

Hu X.,Shanghai JiaoTong University | Wang D.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2016

The uncertainty of design variables is incorporated to design optimization of ship structure. Since conventional double loop strategy for probabilistic design optimization involves iterative optimization process and probabilistic assessment, a strategy of reliability-based design optimization is proposed by synthesizing kriging model, sequential optimization and reliability assessment (SORA) method and particle swarm optimization (PSO). And the strategy is applied to the problem of reliability-based design optimization of a multipurpose ship. SORA method decouples the process of reliability assessment and optimization, which improves the efficiency of reliability-based optimization. PSO method guarantees the efficiency of calculating global optimal solution in the optimization part of SORA. Kriging model substitutes for time-consuming finite element model calculation in the process of optimization and reliability assessment. And inverse First Order Reliability Method (FORM) is used to calculate reliability index and locate the most probable points (MPP) which is used to shift the boundaries of violated constraints. The optimization results and computing time of the multipurpose ship are verified by the results of finite element (FEM) model calculation and Monte Carlo simulation, which shows that the proposed strategy guarantees the accuracy of solutions and significantly alleviates the computational burden. © Copyright 2016 by the International Society of Offshore and Polar Engineers (ISOPE).

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