Finite Element Analysis of Deformed Legs of Offshore Platform Structures     

LIU  Chuntu 《中国海洋工程》2002,16(3):311-320

The element stiffness matrix of the equivalent beam or pipe element of the deformed leg of the platform is derived by the finite element method. The stresses and displacements of some damaged components are calculated, and the numeri-cal solutions agree well with those obtained by the fine mesh finite element method. Finally, as an application of this method, the stresses of some platform structures are calculated and analyzed.  相似文献   

Wave Attenuation and Friction Coefficient on the Coral-Reef Flat     

朱良生黎满球  张洪生隋世峰 《中国海洋工程》2004,18(1):129-136

Several sets of S4 direction-wave-current-tide meters have been deployed on the coral-reef fiat of Yongshu Reef in the sea area of Nansha Islands. Based on the observational sea wave data, the attenuation characteristics of the waves propagating on the coral reef flat, the bottom friction coefficients and the transfer of wave energy are discussed in the paper. The results show that, in the relative depths of 0. 0613- 0.0867, the wave height attenuation per unit distance of wave propagation is 22.09 %-46.56%, with an average of 31.35 % ; the wave energy, attenuation coefficient, 33.74 %- 53.22%, with an average of 43.61%. The average of the bettom friction coefficients on the coral-reef flat is 0. 1346,which is about 10 times thai on the sand or silt bottom. In the couse of propagation on the reef flat, the waves sustain more loss in high frequency than in low frequency and the spectral energy transfers to the low frequency. These results may be used for reference in island and reef engineering.  相似文献   

An Improved Nearshore Wave Breaking Model Based on the Fully Nonlinear Boussinesq Equations   总被引：1，自引：2，他引：1  

李绍武  李春颖时钟 谷汉斌 《中国海洋工程》2005,19(1):61-71

This paper aims to propose an improved numerical model for wave breaking in the nearshore region based on the fully nonlinear form of Boussinesq equations. The model uses the k equation turbulence scheme to determine the eddy viscosity in the Boussinesq equations. To calculate the turbulence production term in the equation, a new formula is derived based on the concept of surface roller. By use of this formula, the turbulence production in the one-equation turbulence scheme is directly related to the difference between the water portide velocity and the wave celerity. The model is verified by Hansen and Svendsen‘s experimental data (1979) in terms of wave height and setup and sctdown. The comparison between the model and experimental results of wave height and setup and setdown shows satisfactory agreement. The modeled turbulence energy decreases as waves attenuate in the surf zone. The modeled production term peaks at the breaking point and decreases as waves propagate shoreward. It is also suggested that both convection and diffusion play their important roles in the transport of turbulence energy immediately after wave breaking. When waves approach to the shoreline, the production and dissipation of turbulence energy are almost balanced. By use of the slot technique for the simulation of the movable shoreline boundary, wave ranup in the swash zone is well simulated by the present model.  相似文献   

Rheological Properties and Incipient Motion of Cohesive Sediment in the Haine Estuary of China     

白玉川  NG Chiu-on  沈涣庭  王尚毅 《中国海洋工程》2002,(4)

The Haihe cohesive sediment, which is typical in China, is studied systematically for its basic physical and incipient motion properties. Following the requirements of dredging works in the Haihe Estuary, cohesive sediment samples were taken from three locations. Laboratory experiments were conducted to delermine the rheological properties of these samples and to examine the incipient motion of the cohesive sediment. it is found that the cohesive sediment has an obvious yield stress τb, which increases with the mud density in a manner of an exponential function, and so does the viscosity parameter η. The cohesive sediment behaves like a Bingham fluid when its density is below 1. 38 - 1 .40 g/cm3 , and when denser than these values, it may become a power-law fluid. The incipient motion experiment also revealed that the incipient velocity of the cohesive sediment increases with the density in an exponential manner. Therefore, the incipient motion is primarily related to the density, which is different f  相似文献   

Effect of Distortion Ratio on Local Scour Under Tidal Currents and Waves     

窦希萍  董凤舞 《中国海洋工程》2004,18(4):613-627

Five generalized physical models of drfferent distortion ratios were bruit according to DOU Guo-ren‘s similarity theory of total sediment transport modeling for estuarine and coastal regions. Experiments on local scour in front of groins were made under the actions of tidal currents and waves with clear and sediment entraining water. The scour depths under different dynamic actions are compared. The effect of the distortion ratio on the depth of scour hole is discussed. A relationship between scour depths for distorted and undistorted models is given.  相似文献   

Experimental Study of Hydrodynamic Loading on Submarine Composite Pipelines under the Action of Waves and Current     

Ma Liang  Wang Jinying Xing Zhizhuang Sun Shaoshu Professor  Dalian University  Dalian Senior Engineer  China Offshore Oil Engineering Co. 《中国海洋工程》1994,(2)

- This article is aimed at the experimental study of the hydrodynamic loading induced by waves and current acting on the JZ 20-2 submarine composite pipelines. The corresponding hydrodynamic coefficients obtained in this experimental study can be applied to engineering projects.  相似文献   

Linearization methods and the influence of current on the nonlinear hydrodynamic drag force     

Ove T. Gudmestad  Senior Engineer  Jerome J. Connor  Professor of Civil Engineering 《Applied Ocean Research》1983,5(4):184-194

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Oblique and Multi-Directional Random Wave Loads on Vertical Breakwaters   总被引：3，自引：1，他引：3  

俞聿修  李本霞  张宁川 《中国海洋工程》2003,17(2)

1 .IntroductionTraditionally ,thedesignofcoastalstructuresisbasedontheformulaedevelopedforhead onuni directionalwaves .However,wavesusuallyattackabreakwaterobliquely ,formingshort crestedwavesinfrontofthebreakwater.Ontheotherhand ,asthehumanactivityareaisspreading ,thewaterdepthattheconstructionsiteforbreakwatershasatendencytobecomelarge ,andsomebreakwatershavebeenconstructedinwaterareasdeeperthan 6 0minJapan (Tanimotoetal.,1 988) .Theseawaveismulti directionalandrandom ,especiallyindeepwater…  相似文献   

Generation and Deformation of Solitary Waves   总被引：2，自引：6，他引：2  

Chou Chung-Ren Shih Ruey-Syan Professor  Dept. of Harbor  River Engineering  National Taiwan Ocean University . Graduate Student  Dept. of Harbor  River Engineering  National Taiwan Ocean University 《中国海洋工程》1996,(4)

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Numerical Calculation Methods for Wavemaking Response Induced by Explosion in Harbour     

Li Dejun  Shen Guoguang  Wang Rixin Cheng Hong Professor  Dept. of Ocean  Architecture Engineering  Tianjin University  Tianjin Lecturer  Dept. of Ocean  Architecture Engineering  Tianjin University  Tianjin Engineer  Naval Research Centre  P. L. A. of China  Beijing 《中国海洋工程》1995,(4)

Using the axial symmetry results of marker and cell (MAC) method as initial value in this paper, two numerical calculating methods are presented for the late wavemaking response induced by explosion in harbour. One of the methods is the superposition method of the vibration mode based on fluid slosh in container. Another one is the joining method of the MAC results with the shallow wave theory calculation in time domain. As a practical example, it is conducted to the numerical calculation about 1000 ton TNT equivalent explosion within touch of water surface. The results show that it can be rationally described with the methods to the wavemaking progress and character. The numerical results are identical with the observed scene on the spot experiment. The methods are simple and applicable in the engineering design.  相似文献