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China Ocean Engineering 2023年第2期37卷 312-322页

作者： XU Fu-min zheng jin-hai YA Han-zheng XING Tian Key Laboratory of Ministry of Education for Coastal Disaster and Protection Hohai UniversityNanjing 210098China College of Harbor Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

Waves play a major role in the ocean phenomena in the Gulf of Guinea(GoG). In order to reveal the spatial-temporal distribution characteristics and the propagation mechanism of waves from the South Atlantic Ocean to the GoG, 4typical points located in mid-latitude of South Atlantic(14°30′W, 30°0′S), south of the GoG(10°30′W, 15°0′S), offshore of the GoG(0°0′, 0°0′) and near shore of the GoG(6°4′58.8″W, 4°3′36″S) are selected, and waves from Atlantic Ocean to GoG are simulated by using a two-layer-nesting wave numerical model SWAN(Simulating Waves Nearshore). The results show that the hybrid waves(waves hereafter) and the swells have strong relationship with local wind in Roaring Forties and at mid-latitude of South Atlantic Ocean, while there is no obvious correlation between waves and local winds in the GoG. Swells are generated in the South Atlantic Ocean and propagate into the GoG. 2D wave spectra at the four selected typical points are simulated. The spectral pattern and wave component structure indicate that the wave system in GoG is dominated by the S-SW swells generated from Roaring Forties and mid-latitude of South Atlantic, whether it is at maximum(2.2-2.8 m), medium(1.8-2.2 m) or minimum(1.2 m) significant wave height in the GoG during simulation period.

关键词： Gulf of Guinea wave characteristics 2D wave spectra swell roaring forties

Study on the Propagation and Focusing Mechanism of Long Waves over A Submerged Atoll

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China Ocean Engineering 2023年第2期37卷 204-217页

作者： FU Dan-juan LIU Bi-jin zheng jin-hai WANG Gang CHEN Bi-qin School of Civil Engineering and Architecture Xiamen University of TechnologyXiamen 361024China hainan Institute Zhejiang UniversitySanya 572025China Key Laboratory of Coastal Disaster and Protection Ministry of EducationHohai UniversityNanjing 210098China Fujian Polytechnic of Information Technology Fuzhou 350003China

An analytical solution for long waves propagating over a submerged atoll is established. The atolls involved in this study are annular coral reefs with large lagoons in the middle, and the expression of the cross section is a trinomial function of the radial distance, i.e., h=ar(2s)-br~s+h_0, where s is the positive rational number. This analytical solution extends the theory by Wang et al.(2018) as s is no longer limited to s=2/m, where m is the positive integer. In addition, by adjusting the terrain parameters properly, the analytic solution can be degenerated to describe the wave propagation over topography with a hump or pit. According to the relationship between wave rays and wave energy, the distribution characteristics and formation mechanism of energy over the topography are expounded. When the lagoon is non-existent, all wave rays converge at the x-axis, which results in an abrupt amplification of the wave amplitude around the convergence point. When a lagoon is mounted on the top of the atoll, the rays are scattered due to the refraction of the lagoon, and only some rays converge at the symmetrical axis and the ridges on both sides,which results in the amplification of wave amplitudes in these areas.

关键词： long waves analytic solution wave scattering submerged atoll wave propagation

NUMERICAL WAVE FLUME WITH IMPROVED SMOOTHED PARTICLE HYDRODYNAMICS

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Journal of Hydrodynamics 2010年第6期22卷 773-781页

作者： zheng jin-hai SOE Mee Mee ZHANG Chi HSU Tai-Wen State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing210098 China Department of Hydraulic and Ocean Engineering National Cheng Kung University Tainan 701 China

This paper presents an improved Nearest Neighboring Particle Searching （NNPS） technique for numerical modeling of water waves with the Smoothed Particle Hydrodynamics （SPH） method. The proposed technique differs from others by introducing the concept of Inner and Outer Particle Searching （lOPS） and shifting most of advanced CPU operations into simple addition operations. The IOPS method is shown to significantly improve the computational efficiency and reduce the CPU time especially for large number of particles, based on comparisons with other two NNPS methods. This method is implemented in a 2DV numerical wave flume conducted by the SPH method. Three test cases are examined, including generations and propagations of dam-breaking induced waves, solitary wave and irregular wave. Calculated results are in good agreements with experimental data and theoretical solutions with fairly satisfactory CPU time-consuming. The wave motions observed in physical facilities are successfully reproduced by the SPH numerical wave flume, revealing its robust capability of modeling realistic wave propagation and substantial potential for a wide variety of hydrodynamic problems.

关键词： particle searching technique Smoothed Particle Hydrodynamics (SPH) numerical wave flume Navier-Stokes equation

Wave Power Focusing due to the Bragg Resonance

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China Ocean Engineering 2017年第4期31卷 458-465页

作者： TAO Ai-feng YAN jin WANG Yi zheng jin-hai FAN Jun QIN Chuan State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China College of Harbor Coastal and Offshore Engineering Hohai University Nanjing 210098 China College of Energy and Electrical Engineering Hohai University Nanjing 210098 China

Wave energy has drawn much attention as an achievable way to exploit the renewable energy. At present, in order to enhance the wave energy extraction, most efforts have been concentrated on optimizing the wave energy convertor and the power take-off system mechanically and electrically. However, focusing the wave power in specific wave field could also be an alternative to improve the wave energy extraction. In this experimental study, the Bragg resonance effect is applied to focus the wave energy. Because the Bragg resonance effect of the rippled bottom largely amplifies the wave reflection, leading to a significant increase of wave focusing. Achieved with an energy conversion system consisting of a point absorber and a permanent magnet single phase linear motor, the wave energy extracted in the wave flume with and without Bragg resonance effect was measured and compared quantitatively in experiment. It shows that energy extraction by a point absorber from a standing wave field resulted from Bragg resonance effect can be remarkably increased compared with that from a propagating wave field （without Bragg resonance effect）.

关键词： wave power experiment Bragg resonance

Experimental Study on the Cyclic Behavior of Monopiles in Fine Sandy Beds Under Regular Waves

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China Ocean Engineering 2017年第5期31卷 607-617页

作者： HUANG Ting zheng jin-hai ZHANG Ji-sheng YUAN Yu WU Bin Key Laboratory of Coastal Disaster and Defence Ministry of EducationHohai University College of Harbor Coastal and Offshore EngineeringHohai University

This paper presents an experimental study on the wave-induced behavior of monopiles. Laboratory experiments were conducted at the constant initial state of the sandy beds in a wave flume with a soil trench. The responses of the pile- head displacement, the pile strain and the pore water pressure on regular waves were investigated. The experimental results show that the monopiles lean along the direction of the wave progression and the inclination increases with the duration of wave actions. The pile-head displacement （consisting of the permanent displacement and cyclic displacement） increases as the wave height increases, especially more significantly for the permanent displacement. The head-fixed pile suffers from larger wave load than that on the head-free pile under the same wave condition. Increasing pile diameter or fixing fins on the monopile is effective in reducing the pore water pressure in the upper part of the bed and the permanent displacement.

关键词： monopile fine sandy bed displacement wave load pore water pressure

On the Downshift of Wave Frequency for Bragg Resonance

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China Ocean Engineering 2022年第1期36卷 76-85页

作者： PENG Ji TAO Ai-feng FAN Jun zheng jin-hai LIU Yu-ming Key Laboratory of Ministry of Education for Coastal Disaster and Protection Hohai UniversityNanjing 210098China Quality Supervision Department China Renewable Energy Engineering InstituteBeijing 100120China College of Harbor Coastal and Offshore EngineeringHohai UniversityNanjing 210098China Department of Mechanical Engineering Massachusetts Institute of TechnologyCambridge 02139USA

For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance *** critical wave frequency,at which the peak reflection coefficient is obtained,has been observed in both physical experiments and direct numerical simulations to be downshifted from the well-known theoretical *** has long been speculated that the downshift may be attributed to higher-order rippled bottom and free-surface boundary effects,but the intrinsic mechanism remains *** a regular perturbation analysis,we derive the theoretical solution of frequency downshift due to third-order nonlinear effects of both bottom and free-surface *** is found that the bottom nonlinearity plays the dominant role in frequency downshift while the free-surface nonlinearity actually causes frequency *** frequency downshift/upshift has a quadratic dependence in the bottom/free-surface *** bottom leads to a larger frequency downshift relative to the monochromatic *** addition,direct numerical simulations based on the high-order spectral method are conducted to validate the present *** theoretical solution of frequency downshift compares well with the numerical simulations and available experimental data.

关键词： gravity surface wave Bragg resonance frequency downshift regular perturbation analysis

THREE-DIMENSIONAL NUMERICAL MODELLING OF SUBMERGED DIKE ALIGNMENT IN CURVED ESTUARINE CHANNEL

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Journal of Hydrodynamics 2005年第5期17卷 601-606页

作者： zheng jin-hai LIU Ying-qi YAN Yi-xin ZHU Yu-liang Research Institute of Coastal and Ocean Engineering Hohai University Nanjing 210098 China

Submerged dikes were frequently built in curved estuarine channels to improve navigational conditions. A three-dimensional numerical model of tidal motions was developed to simulate flows through the submerged dike alignment in curved estuarine reach of complex bathymetry on the basis of satisfactory calibrations. Through the analysis of the morphological characteristics of the curved channel of the Huangpu River mouth in the Yangtze River Delta, a submerged dike alignment project was examined. The effect of the navigation channel improvement project and its influence on the flow regimes, the navigational conditions, the flood control and the operating conditions of harbours within the adjacent water area were evaluated, and the technical feasibility of the navigation channel improvement scheme was demonstrated.

关键词： submerged dike alignment three-dimensional numerical model curved estuarine channel morphological analysis

Influence of Spur Dike on Hydrodynamic Exchange Between Channel and Shoal of Generalization Estuary in Physical Model Test

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China Ocean Engineering 2017年第5期31卷 624-630页

作者： JIAO Zeng-xiang Dou Xi-ping zheng jin-hai ZHANG Xin-zhou GAO Xiang-yu Nanjing Hydraulic Research Institute College of Harbor Coastal and Offshore EngineeringHohai University Key Laboratory of Port Waterway and Sedimentation Engineering of the Ministry of Transport

Widely applied in maintaining estuarial waterway depth, the spur dike has played an important role in currents and sediment exchange between channel and shoal and sediment back-silting in the channel. Through establishing a generalized physical model at a bifurcated estuary and conducting current tests under the joint action of runoff and tide, the influence of the spur dike length on current exchange between channel and shoal is analyzed. Results show that when the spur dike length reaches a certain value, the direction of the flow velocity shear front between the channel and shoal will change. The longer the spur dike, the larger the transverse fluctuating velocity at the peak of flood in the channel shoal exchange area, while the transport of the transverse hydrodynamics is obvious in the process of flood. There is an optimum length of spur dike when the shear stress in the channel and the longitudinal velocity in flood and ebb reach the maximum, and the flow velocity will decrease when the spur dike length is smaller or larger than the optimum. For a certain length of spur dike, the larger the channel shoal elevation difference, the larger the peak longitudinal flow velocity in the middle of the navigation channel in flood and ebb. However, the transverse flow velocity will first decrease and then increase. The transverse transportation is obvious when the channel shoal elevation difference increases.

关键词： spur dike hydrodynamics flow velocity channel shoal exchange physical model

A Method for the Damage Detection of Pile Foundation in High-Pile Wharf Based on A Curvature Mode Deletion Model

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China Ocean Engineering 2020年第6期34卷 871-880页

作者： WANG Qi-ming ZHU Rui-hu zheng jin-hai WANG Ning LUO Meng-yan CHE Yu-fei College of Science Hohai UniversityNanjing 210098China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

As the top of the pile foundation in high-pile wharf is connected to the superstructure and most of the pile bodies are located below the water surface, traditional damage detection methods are greatly limited in their application to pile foundation in service. In the present study, a new method for pile foundation damage detection is developed based on the curve shape of the curvature mode difference(CMD) before and after damage. In the method, the influence at each node on the overall CMD curve shape is analyzed through a data deletion model, statistical characteristic indexes are established to reflect the difference between damaged and undamaged units, and structural damage is accurately detected. The effectiveness and robustness of the method are verified by a finite element model(FEM) of high-pile wharf under different damage conditions and different intensities of Gaussian white noise. The applicability of the method is then experimentally validated by a physical model of high-pile wharf. Both the FEM and the experimental results show that the method is capable of detecting pile foundation damage in noisy curvature mode and has strong application potential.

关键词： high-pile wharf pile foundation curvature mode data deletion model damage detection

On Centralizer Subalgebras of Group Algebras

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Communications in Mathematical Research 2011年第3期27卷 227-233页

作者： LI zheng-XING hai jin-KE School of Mathematics Qingdao University Qingdao 266071

Let G be a finite group, H ≤ G and R be a commutative ring with an identity 1R. Let CRG（H）={α ∈ RG｜αh = hα for all h ∈ H）, which is called the centralizer subalgebra of H in RG. Obviously, if H=G then CRG（H） is just the central subalgebra Z（RG） of RG. In this note, we show that the set of all H- conjugacy class sums of G forms an R-basis of CRG（H）. Furthermore, let N be a normal subgroup of G and γthe natural epimorphism from G to G to G/N. Then γ induces an epimorphism from RG to RG, also denoted by % We also show that if R is a field of characteristic zero, then γ induces an epimorphism from CRG（H） to CRG（H）, that is, 7（CRG（H）） = CRG（H）.

关键词： group ring centralizer subalgebra H-conjugacy class H-conjugacy class sum