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A Piston-Type Active Absorbing Wavemaker System with Delay Compensation

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China Ocean engineering 2015年第6期29卷 917-924页

作者：杨洪齐李木国柳淑学张群王静 State Key Laboratory of Coastal and offshore engineering Dalian University of Technology

Physical model tests with highly reflective structures often encounter a problem of multiple reflections between the structures and the wavemaker. This paper presents a piston-type active absorbing wavemaker system which can absorb most of the reflections. Based on the first-order wavemaker theory, a frequency domain absorption transfer function is modeled. Its time realization can be achieved by designing an IIR digital filter, which is used to control the absorbing wavemaker system. In a real system, time delays often exist in the wave making process. Thus a delay compensation term to the transfer function is proposed. Experimental results show that the system performs well for both regular and irregular waves with periods from 0.6 s to 2.0 s, and the absorption capability is larger than 96.5% at target wave fields.

关键词： wavemaker active absorption IIR digital filter time delay

Experimental Study on 2-D Focusing Wave Run-up on A Vertical Cylinder

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China Ocean engineering 2010年第3期24卷 499-512页

作者：柳淑学孙一艳李金宣臧军 State Key Laboratory of Coastal and offshore engineering Dalian University of Technology department of Architecture and Civil engineering Science University of Bath

In this paper,the focused wave groups with different parameters and their actions on a vertical cylinder are experimentally studied. The harmonic wave characteristics of the focusing waves are analyzed by the addition and subtraction of the crest and trough focusing waves. The analyzed results show that higher order harmonics can be generated because of the interaction of component waves. Nonlinearity increases with the inputted wave amplitude and the frequency width increment. Further, the wave run-up around the vertical circular cylinder is experimentally studied. It increases with the wave steepness and the relative cylinder diameter increase. However, the variations of wave run-up around the circular cylinder are different. The researches provide a reference for further numerical studies.

关键词： wave focusing nonlinearity vertical circular cylinder wave run-up

Investigation on Cutting Stability of Jacket in Decommissioning Process

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China Ocean engineering 2015年第5期29卷 649-661页

作者：李美求段梦兰黄一 department of Architecture engineering Dalian University of Technology School of Mechanical engineering Yangtze University offshore Oil/Gas Research Center China University of Petroleum

Jacket cutting operation is one of the most complicated and highest risk operations in the process of decommissioning offshore piled platform, the security and stability of which must be assured. In this paper, the current research on offshore structure removal and jacket cutting is introduced, on the basis of which the types of load along with the load calculation method are determined. The main influences on the stability of a jacket in cutting are analyzed. The experiment test plan is drawn by using orthogonal testing method, and the formula of critical load during the cutting procedure is deduced by differential evolution algorithm. To verify the method and results of this paper, an offshore piled platform to be decommissioned in the South China Sea is taken for an example, and the detailed schedule for jacket cutting is made with the three-dimensional finite element model of the jacket established. The natural frequency, stress, strain and stability of the jacket during cutting process are calculated, which indicates that the results of finite element analysis agree well with that of the deduced formula. The result provides the scientific reference for guaranteeing the safety of jacket in cutting operation.

关键词： stability jacket cutting operation piled platforms decommissioning

An Overview of Deepwater Pipeline Laying Technology

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China Ocean engineering 2008年第3期22卷 521-532页

作者：李志刚王琮何宁赵冬岩 China offshore Oil engineering Co. Ltd.

The technology and methods involved in pipeline laying in shallow water have evolved to the level of routine and commonplace. However, regarding the unexpected deepwater complexity, the traditional pipeline laying techniques have to confront many new challenges arisen from the increase of the water depth, diameter of the pipe and the welding difficuhy, all of which should be modified and/or innovated based on the existed mature experiences. The purpose of this investigation is to outline the existing and new engineering laying techniques and the associated facilities, which can provide some significant information to the related research. In the context, the latest deepwater pipeline laying technology and pipe laying barges of the renowned companies from Switzerland, Norway, Italy etc., are introduced and the corresponding comparison and discussion are presented as well.

关键词： deepwater pipeline pipeline installation method pipe laying barge/vessel

A Coupling Model of Nonlinear Wave and Sandy Seabed Dynamic Interaction

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China Ocean engineering 2007年第1期21卷 77-89页

作者：程永舟王永学蒋昌波 State Key Laboratory of Coastal and offshore engineering Dalian University of Technology department of River and Ocean engineering Changsha University of Science and Technology

In the paper, a weak coupling numerical model is developed for the study of the nonlinear dynamic interaction between water waves and permeable sandy seabed. The wave field solveris based on the VOF （Volume of Fluid） method for continuity equation and the two-dimensional Reynolds Averaged Navier Stokes （RANS） equations with a k-ε closure. The free surface of cnoidal wave is traced through the PLIC-VOF （P/ecewise Linear/nterface Construction）. Blot＇s equations have been applied to solve the sandy seabed, and the u-p fmite dement formulations are derived by the application of the Galerkin weighted-residual procedure. The continuity of the pressure on the interface between fluid and porous medium domains is considered. Laboratory tests were performed to verify the proposed numerical model, and it is shown that the pore-water pressures and the wave heights computed by the VOF-FEM models are in good agreement with the experimental results. It is found that the proposed model is effective in predicting the seabed-nonlinear wave interaction and is able to handle the wave-breakwater-seabed interaction problem.

关键词： nonlinear wave sandy seabed pore water pressure PLIC-VOF method VOF-FEM model

The physical simulation of wave groups and their variations in a wave flume

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Acta Oceanologica Sinica 2013年第11期32卷 68-73页

作者： LIU Si ZHANG Yongliang LIU Shuxue LI Jinxuan XIA Zhisheng State Key Laboratory of Hydroscience and Hydraulic engineering Department of Hydraulic EngineeringTsinghua University State Key Laboratory of Coastal and offshore engineering Dalian University of Technology

The physical simulation method of wave groups in a wave flume is proposed and verified by the exper- iments. The experimental results demonstrate that random waves with desired wave groupiness, which simultaneously includes the wave group height and length, can be generated satisfactorily at the specified position in a wave flume using the proposed method. Furthermore, the transformation properties of the wave groupiness along the fiat-bottomed wave flume are investigated based on the physically simulated waves. Associated proposals with the physical simulation of wave groups are given.

关键词： wave groups wave groupiness physical simulation wave flume

Highly mechanical and high-temperature properties of Cu–Cu joints using citrate-coated nanosized Ag paste in air

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Progress in Natural Science:Materials International 2021年第1期31卷 129-140页

作者： Qian Wang Shuye Zhang Tiesong Lin Pengzhe Zhang Peng He Kyung-Wook Paik State Key Laboratory of Advanced welding and Joining Harbin Institute of Technology department of Materials Science and engineering Korea Advanced Institute of Science and Technology Joining and welding Research Institute Osaka University

Today,a growing number of third-generation semiconductor-based power devices are used in products that can continuously operate at high temperatures for extended periods of ***,traditional tin-lead and lead-free solders are no longer suitable for modern electronic packaging.A common method is to apply Ag paste for bare Cu-Cu joints under an inert or reductive *** this study,the citrate-coated nanosized Ag paste was utilized to generate robust bare Cu-Cu joints under atmospheric *** average size of citrate-coated Ag particles was approximately 4.76 nm after being cleaned by deionized water and *** effects of process parameters,such as cleaning,joining temperature,holding time,and joining pressure,on the mechanical properties of the bare Cu-Cu joints were thoroughly *** washing and joining temperatures resulted in a shear strength increase of up to 28.2 MPa at a joining temperature of 260℃ after seven *** addition,a holding time of 30 min and a joining pressure of 1 MPa were selected as optimal process conditions for the application of citrate-coated nanosized Ag paste onto bare Cu-Cu *** newly developed Cu-Cu joints showed excellent thermal stability at 150℃ using the citrate-coated nanosized Ag *** long-term aging,the joints exhibited stability at 250℃ for 144 h,indicating a good high-temperature reliability for threedimensional integrated circuits(3 D ICs) fabricated under atmospheric conditions.

关键词： Electronic packaging Ag paste Cu–Cu joints Mechanical property Joining morphology

A numerical study of fracture initiation under different loads during hydraulic fracturing

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Journal of Central South University 2020年第12期27卷 3875-3887页

作者： TANG Shi-bin DONG Zhuo WANG Jia-xu MAHMOOD Ahmad State Key Laboratory of Coastal and offshore engineering Dalian University of TechnologyDalian 116024China department of Civil engineering University of Engineering and Technology Peshawar(Bannu Campus)Bannu 28100Pakistan

The fracture initiation behavior for hydraulic fracturing treatments highlighted the necessity of proposing fracture criteria that precisely predict the fracture initiation type and location during the hydraulic fracturing *** the present study,a Mohr-Coulomb criterion with a tensile cut-off is incorporated into the finite element code to determine the fracture initiation type and location during the hydraulic fracturing *** fracture criterion considers the effect of fracture inclination angle,the internal friction angle and the loading conditions on the distribution of stress field around the fracture *** results indicate that the internal friction angle resists the shear fracture ***,as the internal friction angle increases,greater external loads are required to maintain the hydraulic fracture *** to the increased pressure of the injected water,the tensile fracture ultimately determines the fracture initiation ***,the shear fracture preferentially occurs as the stress anisotropy coefficient *** the maximum tensile stress and equivalent maximum shear stress decrease as the stress anisotropy coefficient increases,which indicates that the greater the stress anisotropy coefficient,the higher the external loading required to propagate a new *** numerical results obtained in this paper provide theoretical supports for establishing basis on investigating of the hydraulic fracturing characteristics under different conditions.

关键词： hydraulic fracturing internal friction angle stress anisotropy coefficient finite element method

Tensile and Flexural Properties of Ultra High Toughness Cemontious Composite

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Journal of Wuhan University of Technology(Materials Science) 2009年第4期24卷 677-683页

作者：李贺东徐世烺 State Key Laboratory of Coastal and offshore engineering Dalian University of Technology

The tensile and flexural properties of polyvinyl alcohol （PVA） fiber reinforced ultra high toughness cementitious composite （UHTCC） were investigated. The composite, tested at the age of 14 d, 28 d and 56 d, shows extremely remarkable pseudo strain hardening behavior, saturated multiple cracking and ultra high ultimate strain capacity above 4% under uniaxial loading. Also, the corresponding crack widths are controlled under 50 um even at 56 days age. In the third point bending tests on thin plate specimens, the composite shows ultra high flexural ductility and multiple cracking on the tension surface. The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC. SEM observation on fracture surfaces provides indirect evidence of optimal design for the composite.

关键词： pseudo strain hardening cementitious composite multiple cracking ductility SEM