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Hu J.,Shanghai JiaoTong University | Hu J.,State Key Laboratory of Ocean Engineering | Hu J.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Yin Y.,Shanghai JiaoTong University | And 4 more authors.
Thin-Walled Structures | Year: 2017

Ethylene tetrafluoroethylene (ETFE) cushion structures with the capacities of aesthetical appearance, excellent insulation and high strength-to-weight ratio have attracted considerable attention in recent years. Conventional ETFE cushion structures need fundamental form finding and cutting patterns, resulting in complex analysis and necessary strain compensation. For this reason, this paper focused on a new approach for form finding of flat-patterning ETFE cushions and corresponding nonlinear structural behavior. To achieve these goals, experiments for identifying mechanical properties of ETFE foils and structural behavior of a bubble prototype were carried out. Meanwhile, numerical simulations with Peirce model were performed to evaluate deformation, stress, total strain and plastic strain of flat-patterning ETFE cushions in the development of form finding. Comparisons between experimental and numerical results could obtain following conclusions. Deformation evolution with pressure increment indicated that nonlinear structural behavior was critical for understanding detailed structural behavior. The maximum stress and strain were larger than yield stress and strain, meaning that this form finding approach could consider hardening effects and thus get designed forms of ETFE cushions. The propagation mechanisms of stress and strain were characterized, which originated from edge middle area and propagated toward central area of the ETFE cushion. Moreover, it is found that plastic strain originated at 2000 Pa and reached a maximum value of 2.33% at 4000 Pa. In general, this study could provide useful observations and values for understanding nonlinear structural behavior of flat-patterning ETFE cushions in the development of form finding. © 2017 Elsevier Ltd

Hu J.,Shanghai JiaoTong University | Hu J.,State Key Laboratory of Ocean Engineering | Hu J.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Chen W.,Shanghai JiaoTong University | And 5 more authors.
Applied Energy | Year: 2016

This paper concerns energy performance of ETFE (ethylene tetrafluoroethylene) cushion roof integrated photovoltaic/thermal system (CIPV/T system). An experimental set-up composed of a three-layer ETFE cushion roof and amorphous silicon photovoltaic panels (a-Si PV) has been developed to investigate system energy performance. A series of tests from 10:00 a.m. to 5:00 p.m. were successfully carried out within ambient temperature of around 9 °C and 39 °C in December 2014 and August 2015, respectively. On the whole, experimental results show that this system operated smoothly and steadily. In this study, typical weather conditions ranging from low solar irradiance in winter to strong solar irradiance in summer were selected to investigate system energy performance, including solar energy utilization and structural parameters of ETFE cushion roof. Solar energy utilization could be evaluated by electricity and temperature which represent photovoltaic and thermal performance, respectively. It is found that average total and net electricity were 54.5 W h and 42.9 W h, indicating that this integration ensures the CIPVT system to be independent on external electricity. Meanwhile, measured air temperature inside ETFE cushion roof was 31.2-67.8 °C and it was 16.8-31.0 °C higher than ambient air temperature, showing an attractive potential in collecting thermal energy. Moreover, virtual system efficiency in terms of electricity and thermal energy was 25.5% based on average experimental results and an approximate method. This reasonable system efficiency is due to annealing effects of a-Si PV under high temperature conditions. For temperature distribution of ETFE cushion roof, temperatures on top-layer and bottom-layer ETFE foils were significantly lower than that on middle-layer ETFE foil, resulting in less temperature effects on structural behavior of ETFE cushion roof. This study could provide useful observations and explanations for evaluating energy performance of the CIPVT system concerning solar energy utilization. © 2016 Elsevier Ltd.

Liu Z.,State Key Laboratory of Ocean Engineering | Lin Z.,State Key Laboratory of Ocean Engineering | Liao S.,State Key Laboratory of Ocean Engineering | Liao S.,Shanghai JiaoTong University | Liao S.,King Abdulaziz University
Wave Motion | Year: 2014

The nonlinear interaction between the unidirectional bichromatic wave-train and exponentially sheared current in water of an infinite depth is investigated. The model is based on the vorticity transport equation and the exact free surface conditions, without any assumptions for the existence of small physical parameters. Earlier works of the wave-current interaction were mainly restricted to either current acted on the monochromatic wave or irregular waves limited to irrotational current. Different from these previous works, no constraint is made in our model for amplitudes of the primary wave, and the current owns an exponential type profile along the vertical line. To ensure that the effect of vorticity on the phase velocity is consistent with earlier derivation, the case of a small amplitude wave traveling on the exponentially sheared current is examined firstly. Then the effect of nonlinearity on the phase velocity of primary waves in a bichromatic wave-train is considered. Accurate high-order approximations of the phase velocity are obtained under consideration of both the nonlinear wave self-self and mutual interactions. Finally, the combined effect of vorticity and nonlinearity on the phase velocity is investigated through the case of a bichromatic wave-train propagating on an exponentially sheared current. It is found that the characteristic current slope determines the effect of vorticity on the phase velocity caused by nonlinear wave self-self and mutual interactions, and the surface current strength may amplify/reduce this effect. © 2014 Elsevier B.V.

Yao B.,State Key Laboratory of Ocean Engineering | Yao B.,Shanghai JiaoTong University | Wu G.,University College London
International Journal of Heat and Mass Transfer | Year: 2015

The boundary layer flow over a shrinking sheet into a slot with power-law velocity is analytically studied by a newly developed technique namely homotopy analysis method (HAM). The present work provides analytically new solution branch in different solution areas with the aid of an introduced transformation. The analytical results show that quite complicated behaviors controlled by mass transfer parameters f0 exist, including the known algebraically decaying solution, additional dual solutions and unique solution, which greatly differ from the continuously stretching surface problem. The new analytical solution branch enriches the solution family of the boundary layer flow over a shrinking sheet into a slot with power-law velocity, and helps to understand it deeply. © 2015 Elsevier Ltd. All rights reserved.

Guo J.-H.,Shanghai JiaoTong University | Lu C.-J.,Shanghai JiaoTong University | Lu C.-J.,State Key Laboratory of Ocean Engineering | Chen Y.,Shanghai JiaoTong University | Cao J.-Y.,Shanghai JiaoTong University
Journal of Hydrodynamics | Year: 2010

Based on a suite of CFD code, a homogeneous, multiphase, Reynolds averaged Navier-Stokes solver coupled with a transport cavitation model and a local linear low-Reynolds-number k-ε turbulence model closure was used to simulate the ventilated cavitating flows around a wedge hydrofoil. The gas leakage regimes at the aft of ventilated cavities were investigated. Three gas leakage regimes were observed, and corresponding to each regime, ventilated cavities exhibited a different morphology. The numerical results were compared to corresponding experimental results in qualitative manner. It was found that the general characteristics of the gas leakage regimes and cavity morphology were very reasonably predicted. © 2010 Publishing House for Journal of Hydrodynamics.

Liao S.J.,State Key Laboratory of Ocean Engineering | Liao S.J.,Shanghai JiaoTong University | Liao S.J.,King Abdulaziz University | Wang P.F.,CAS Institute of Atmospheric Physics
Science China: Physics, Mechanics and Astronomy | Year: 2014

Using 1200 CPUs of the National Supercomputer TH-A1 and a parallel integral algorithm based on the 3500th-order Taylor expansion and the 4180-digit multiple precision data, we have done a reliable simulation of chaotic solution of Lorenz equation in a rather long interval 0 ≤ t ≤ 10000 LTU (Lorenz time unit). Such a kind of mathematically reliable chaotic simulation has never been reported. It provides us a numerical benchmark for mathematically reliable long-term prediction of chaos. Besides, it also proposes a safe method for mathematically reliable simulations of chaos in a finite but long enough interval. In addition, our very fine simulations suggest that such a kind of mathematically reliable long-term prediction of chaotic solution might have no physical meanings, because the inherent physical micro-level uncertainty due to thermal fluctuation might quickly transfer into macroscopic uncertainty so that trajectories for a long enough time would be essentially uncertain in physics. © Science China Press and Springer-Verlag Berlin Heidelberg 2014.

Ma L.,Shanghai JiaoTong University | Ma L.,State Key Laboratory of Ocean Engineering | Xu Y.-S.,Shanghai JiaoTong University | Xu Y.-S.,State Key Laboratory of Ocean Engineering | And 3 more authors.
Hydrogeology Journal | Year: 2014

Distributed piles are often installed in the foundation pit in sandy soil before dewatering. Hydraulic conductivity should be estimated considering the block effect of piles on groundwater seepage. Research shows that the effective medium theory (EMT) could be used to calculate the equivalent hydraulic conductivity (keq) of a heterogeneous medium with other material inclusions. In order to verify the applicability of EMT in an aquifer with piles, an experimental investigation is conducted. In this experiment, a sandy soil is considered as an aquifer and polyvinylchloride pipes are adopted as piles. Piles are distributed in rectangular and triangular layouts. The relationship between keq of the aquifer and the volume replacement ratio is plotted for these two layouts. The results indicate that EMT could well predict keq for the cases with the rectangular layout; however, for triangular layouts, the prediction becomes poor. To provide a better prediction of keq of the aquifer with piles distributed in a triangular layout, a modified EMT (MEMT) is proposed, in which a correction factor is adopted considering different layouts of piles. The MEMT can provide better keq predictions for an aquifer with piles in the triangular layout pattern than those obtained using the EMT. © 2013 Springer-Verlag Berlin Heidelberg.

Jian H.,Shanghai JiaoTong University | Xiong L.,Shanghai JiaoTong University | He Y.,Shanghai JiaoTong University | Xiao X.,Shanghai JiaoTong University | Xiao X.,State Key Laboratory of Ocean Engineering
Frontiers in Microbiology | Year: 2015

The SOS response addresses DNA lesions and is conserved in the bacterial domain. The response is governed by the DNA binding protein LexA, which has been characterized in model microorganisms such as Escherichia coli. However, our understanding of its roles in deep-sea bacteria is limited. Here, the influence of LexA on the phenotype and gene transcription of Shewanella piezotolerans WP3 (WP3) was investigated by constructing a lexA deletion strain (WP3ΔlexA), which was compared with the wild-type strain. No growth defect was observed for WP3ΔlexA. A total of 481 and 108 genes were differentially expressed at 20 and 4°C, respectively, as demonstrated by comparative whole genome microarray analysis. Furthermore, the swarming motility and dimethylsulfoxide reduction assay demonstrated that the function of LexA was related to temperature. The transcription of the lexA gene was up-regulated during cold acclimatization and after cold shock, indicating that the higher expression level of LexA at low temperatures may be responsible for its temperature-dependent functions. The deep-sea microorganism S. piezotolerans WP3 is the only bacterial species whose SOS regulator has been demonstrated to be significantly influenced by environmental temperatures to date. Our data support the hypothesis that SOS is a formidable strategy used by bacteria against various environmental stresses. © 2015 Jian, Xiong, He and Xiao.

Hu X.,Shanghai JiaoTong University | Chen J.-J.,Shanghai JiaoTong University | Chen J.-J.,State Key Laboratory of Ocean Engineering
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

An FEM model for a single pile embedded in a saturated seabed is proposed to study the interactive behavior between pile and seabed soil. Fluid-soil coupling and contact behavior on interface is considered, and the quasi-static method is adopted to simulate the crested short wave-induced load on seabed surface. Based on the numerical results, responses of pore water pressure and stress seabed soils under the wave load are investigated, and the deformation and internal force of the single pile are discussed. Two different methods to simulate the pile-soil interface are discussed with a comparison to the greenfield seabed model. The results show that the pore water pressure increases obviously near the bottom of pile, and the lateral displacement of pile is mainly affected by soil. Moreover, the pore water pressure and stress are overestimated by the pile-soil coupled model, and the stress concentration at bottom of pile is more obvious than that by the pile-soil contact model. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.

Xu Y.-S.,Shanghai JiaoTong University | Xu Y.-S.,Chengdu University of Technology | Huang R.-Q.,Chengdu University of Technology | Han J.,University of Kansas | And 3 more authors.
Natural Hazards | Year: 2013

To control land subsidence due to groundwater withdrawal, it is important to estimate allowable withdrawn volume of groundwater in a soft deposit. This technical note presents a simple approach for estimating the allowable withdrawn volume of a deposit. A regression analysis method was used based on measured land subsidence and recorded net withdrawn volume. This approach was proposed based on the principle of soil compression at different effective stresses, i. e. the soil compression is small when the consolidation stress is lower than the yield stress of the deposit, but large when the consolidation stress is higher than the yield stress. Two case studies are presented in this technical paper to demonstrate how to use the simple approach to estimate the allowable withdrawn volume. © 2013 Springer Science+Business Media Dordrecht.

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