Beta Distribution of Surface Elevation of Random Waves   总被引：2，自引：0，他引：2  

ZHANG  Jun 《中国海洋工程》2001,(1):53-60

A probability density function (PDF) is derived of beta distribution with both λ3 (skewness) and λ4 (kurtosis) as parameters for weakly nonlinear wave surface elevation by use of a method recently proposed by Srokosz. This PDF not only has a simpler form than the well-known Gram-Charlier Series PDF derived by Longuet-Higgins. but also overcomes an obvious shortcoming of the latter that when the series is unsuitably truncated, the resulting PDF is locally negative. To test the derived beta PDF, laboratorial experiments of wind waves are conducted. The experimental data indicate that the theoretical requirements of the parameters in the beta PDF are fulfilled. The experimental results show that the present PDF is in better agreement with the measured data than the beta PDF only including parameter λ3, and also than the Gram-Charlier Series PDF truncated up to the term of H6.  相似文献   

Effect of Internal Flow on Vortex-Induced Vibration of Submarine Free Spanning Pipelines     

娄敏 丁坚郭海燕  董晓林 《中国海洋工程》2005,19(1):147-154

At present, most researches on the vortex-induced vibration of submarine free spanning pipelines ignore the effect of internal flowing fluid; furthermore, there are no research reports considering the coupling effect of internal and external fluid with the free span. In this paper, combining Iwan‘s wake oscillator model with the differential equation derived for the dynamic response of submarine free spanning pipelines with inclusion of internal flow, the pipe-fluid coupling equations are developed to investigate the effect of internal flow on the vortex-induced vibration of the free spans. The finite dement approximation is implemented to derive the matrix equations of equilibrium. The Newmark method combined with simple iteration is used to solve the system of equations. The results indicate that the internal fluid flow may cause the shift of resonance band to the lower frequency and a slight decrease in the peak value; the effect will be mare pronounced with the increase of the span length and can be weakened in the presence of the axial tension.  相似文献   

Vertical 2D Modeling of Free Surface Flow with Hydrodynamic Pressure Using SIMPLE Arithmetic in σ Coordinates     

吴修广沈永明  郑永红 《中国海洋工程》2004,18(1):79-92

A numerical model for shallow water flow has been developed based on the unsteady Reynolds-averaged Navier-Stokes equations with the hydrodynamic pressure instead of hydrostatic pressure assumption. The equations arc transformed into the a-coordinate system and the eddy viscosity is calculated with the standard k -ε turbulence model. The control volume method is used to discrete the equations, and the boundary conditions at the bed for shallow water models only include vertical diffusion terms expressed with wall functions. And the semi-implicit methed for pressure linked equation arithmetic is adopted to solve the equations. The model is applied to the 2D vertical plane flow of a current over two steep-sided trenches for which experiment data are available for comparison and good agreement is obtained. And the model is used to predicting the flow in a channel with a steep-sided submerged breakwater at the bottom, and the streamline is drawn.  相似文献   

Offshore Design Waves for Dayaowan Port Area of Dalian Port     

Weng Keqin Guest Associate Professor  Hydraulic  Hydro-Power Engineering Dept.  Tsinghua University  Beijing 《中国海洋工程》1996,(2)

This paper introduces the calculating procedure of the offshore design waves for the Dayaowan port area of Dalian Port. Some suggestions are proposed about the conventional calculating methods with measured waves data.  相似文献   

Behavior of Deformation and Strength of Concrete Under Biaxial Stresses     

Song Yupu  Zhao Guofan Associate Professor  Dalian University of Technology  Dalian Professor  Dalian University of Technology  Dalian 《中国海洋工程》1991,(3)

The study of the behavior of concrete under biaxial stresses is essential to the design of offshore concrete platforms. Using the multiaxial test apparatus developed by the authors, the deformation and strength of concrete under biaxial stresses are studied experimentally. Based on the test data, an endochronic damage constitutive model and a failure criterion are proposed. According to the above model, an incremental nonlinear iterative programme is developed, and a plate sample in plane stress state is analyzed.  相似文献   

Long-Term Joint Distribution of One-Tenth Large (or Significant) Wave Height with Average Period     

Pan Jinchang Associate Professor  Dalian University of Technology  Dalian 《中国海洋工程》1992,(4)

- In this paper, by using the wave data from a few oceanographic observation stations in the coastal zone of the Yellow Sea, the East China Sea and the South China Sea, the long-term joint distribution of the one-tenth large (or significant) wave height with average period is studied. The statistical data demonstrate that the long- term distribution of the one- tenth wave height or average period fits the log-normal distribution, thus the joint distribution also fits the two-dimensional log-normal distribution. Then the conditional probability distribution of the average period is derived, and the range as well as the mode of the average wave period corresponding to a certain return period of wave height can be calculated easily.  相似文献   

Pressure Tight Piston Corer ——A New Approach on Gas Hydrate Investigation     

秦华伟顾临怡  李世伦朱亮 陈鹰 《中国海洋工程》2005,19(1):121-128

A pressure tight sediment samphng technology, which can be introduced into the modification of the piston corer to accommedate the investigation of gas hydrate, is put forward. In this paper, the three basic rules of the technology are analyzed in detail: specimen transferring rule, seal self-tightening rule and semi-active pressure holding rule. Based on these, the structure of the pressure tight piston corer is put forward and its working principle is analyzed. Finally, a pressure tight sediment sampler, to which the same technology is apphed, is researched through experiments. Results show that the sampler based on the above-mentioned theory has a good ability in samphng and in -situ pressure holding.  相似文献   

Design Curves for Mooring Lines of Turret Mooring Systems   总被引：1，自引：0，他引：1  

Gao Jie Tan Jiahua Chen Xiaohong Associate Professor  Shanghai Jiao Tong University  Shanghai Professor  Shanghai Jiao Tong University  Shanghai Lecturer  Shanghai Jiao Tong University  Shanghai 《中国海洋工程》1997,(4)

This paper presents a series of design curves to aid in the selection of turret mooring systemsfor tankers based Floating Production Storage and Offloading(FPSO)systems.These curves are appropri-ate to water depths ranging from 100m to 600m.The curves can be used as a preliminary design tool,al-lowing the designer to quickly evaluate alternative mooring system configurations,including the numberof mooring lines,the characteristics of chain and wire rope to be deployed and the initial tension.With aknowledge of the total environmental force and vessel motion characteristics,the designer can determinethe appropriate system for closer evaluation.  相似文献   

Groupiness of Sea Waves and Their Characteristic Parameters   总被引：1，自引：0，他引：1  

Yu Yuxiu Gui Manhai Professor  Dept. of Civil Eng. Dalian University of Technology  Dalian Master  Dept. of Civil Eng. Dalian University of Technology  Dalian 《中国海洋工程》1996,(1)

Three methods for studying wave groups and their main parameters for describing wave groupiness are reviewed in this paper. Then they are analyzed and compared combined with field data from both aspects of group height and group length. A method and two parameters that can describe wave groupiness are suggested. The groupiness parameters of sea waves at three field stations are given. The effects of groupiness on both distributions of the wave height and the phase of component waves are investigated. The effects of datum length on the calculated value of grouping parameters are also discussed.  相似文献   

An Engineering Computational Method of Calculating Wave Forces on the Mat and Platform''''s Sit-on-Bottom Stability     

Gu Jianming Pan Bin Postgraduate  Dept. of Naval Architecture  Ocean Engineering  Shanghai Jiao Tong University  Shanghai Lecturer  Dept. of Naval Architecture  Ocean Engineering  Shanghai Jiao Tong University  Shanghai 《中国海洋工程》1993,(1)

- In this paper, an engineering method is employed to calculate the horizontal and vertical wave forces on the mat of the submersible platform under Froude-Krylov hypothesis. According to some model tests, appropriate diffraction coefficients are selected. And the results of the formulae given in the paper agree satisfactorily with those experimental data now available. The proposed computational method is effective and convenient to use in evaluating the horizontal and vertical wave forces on the mat. An exmaple is also given in this paper. Finally, the effects of the vertical wave force on the platorm's sit-on-bottom stability are analyzed.  相似文献