Multi-Objective Fuzzy Optimum Design Based on Reliability for Offshore Jacket Platforms     

KANG  Haigui 《中国海洋工程》2001,(4):467-478

In consideration of the fuzzy constraint boundary and through analysis of structural reliability, a model of structural fuzzy optimum design is established based on reliability for offshore jacket platforms. According to the characteristics of offshore jacket platforms, the tolerance coefficient of the constraint boundary is determined with the fuzzy optimization method. The optimum level cut set which is the intersection of the fuzzy constraint set and fuzzy objective set, is determined with the bound search method, and then the fuzzy optimum solution to the fuzzy optimization problem is obtained. The central offshore platform SZ36-1 is designed with the fuzzy optimum model based on reliability; the results are compared with those from deterministic optimum design and fuzzy optimum design. The tendency of design variables in the above three methods and its reasons are analyzed. The results of an example show that the fuzzy optimum design based on reliability is stable and reliable.  相似文献   

几种抗生素对褐藻酸降解菌No.20菌株的抑菌作用及其对海带育苗防病应用的初步研究     

李进道  陈 《中国海洋大学学报(自然科学版)》1984,(1)

多年来,在海带人工育苗过程中时常出现烂苗或掉苗现象,给海带育苗和供苗工作造成严重威胁。引起海带幼苗脱落和腐烂的原因是多方面的,但是微生物的作用是重要的因素之一,褐藻酸降解细菌是海带的重要致病因子。 目前,海带育苗单位虽然采用某些措施,企图控制褐藻酸降解菌的发展,以期达到  相似文献   

Modeling of Motion of Particle Clouds Formed by Dumping Dredged Material   总被引：7，自引：0，他引：7  

YING  Xinya 《中国海洋工程》2001,(1):85-96

The motion of particle clouds formed by dumping dredged material into quiescent waters is experimentally and numerically studied. In the numerical model, the particle phase is modeled by the dispersion model, and turbulence is calculated by the large eddy simulation. The governing equations, including the filtered Navier-Stokes equations and mass transport equation, are solved based on the operator-splitting algorithm and an implicit cubic spline interpolation scheme. The eddy viscosity is evaluated by the modified Smagorinsky model including the buoyancy term. Comparisons of main flow characteristics, including shape, size, average density excess, moving speed and the amount of particles deposited on the bed, between experimental and computational results show that the numerical model well predicts the motion of the cloud from the falling to spreading stage. The effects of silt-fence on the motion of the particle cloud are also investigated.  相似文献   

Comparison of Linear Level I Green-Naghdi Theory with Linear Wave Theory for Prediction of Hydroelastic Responses of VLFS   总被引：4，自引：0，他引：4  

SONG  Hao 《中国海洋工程》2002,16(3):283-300

Very Large Floating Structures (VLFS) have drawn considerable attention recently due to their potential significance in the exploitation of ocean resources and in the utilization of ocean space. Efficient and accurate estimation of their hydroelastic responses to waves is very important for the design. Recently, an efficient numerical algorithm was developed by Ertekin and Kim (1999). However, in their analysis, the linear Level I Green-Naghdi (GN) theory is employed to describe fluid dynamics instead of the conventional linear wave (LW) theory of finite water depth. They claimed that this linear level I GN theory provided betler predictions of the hydroelastic responses of VLFS than the linear wave theory. In this paper, a detailed derivation is given in the conventional linear wave theory framework with the same quantity as used in the linear level I GN theory framework. This allows a critical comparison between the linear wave theory and the linear level I GN theory. it is found that the linear level  相似文献   

Improvements on Mean Free Wave Surface Modeling   总被引：1，自引：0，他引：1  

DONG  Guo-hai 《中国海洋工程》2002,16(4):549-560

Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream funetion wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker indcx in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al. , 1992), with Time-Operator-Split-ting (TOS) used for the treatment of the source terms. This method allows a small number of eomputational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation is solved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).  相似文献   

Reflection of Oblique Incident Waves by Breakwaters with Partially-Perforated Wall   总被引：11，自引：6，他引：11  

LI  Yucheng 《中国海洋工程》2002,16(3):329-342

The reflection of oblique incident waves from breakwaters with a partially-perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigenfunction expansion method is applied to expand velocity poten-tials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with experimental data. The effect of porosity, the relative chamber width, the relative water depth in the wave absorbing chamber and the water depth in front of the structure are discussed.  相似文献   

Numerical Simulation of Wave Height and Wave Set-Up in Nearshore Regions   总被引：2，自引：3，他引：2  

ZHENG  Yonghong 《中国海洋工程》2001,(1):15-23

Based on the time dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation, and then a practical method for the simulation of wave height and wave set-up in nearshore regions is presented. The variation of the complex wave amplitude is numerically simulated by use of the parabolic mild slope equation including the effect of wave energy dissipation due to wave breaking. The components of wave radiation stress are calculated subsequently by new expressions for them according to the obtained complex wave amplitude, and then the depth-averaged equation is applied to the calculation of wave set-up due to wave breaking. Numerical results are in good agreement with experimental data, showing that the expression for the energy dissipation factor is reasonable and that the new method is effective for the simulation of wave set-up due to wave breaking in nearshore regions.  相似文献   

Numerical Prediction of Regular Wave Breaking on Very Gentle Slopes     

LI  Yucheng 《中国海洋工程》2002,16(1):79-87

Regular wave deformation and breaking on very gende slopes is calculated by Mixed-Eulerian-Lagrangian procedure. The velocity potentials and their normal derivatives on the boundary are calculated through the mixed 0-1 boundary element method. The wave elevation and the potentials of time-stepping integration are detertnined by the 2nd-order Taylor expansion at the nodes of free surface boundary elements. During calculation the x-coordinates of the free surface element nodes are supposed to remain unchanged, i.e. the partial derivatives of wave elevation and potentials with respect to x are considered as zero. The numerical results of asymmetric parameters of breaking waves are verified by experimental study. It is shown that when the wave asymmetry is weak, the maximum horizontal velocity of water particales occurs at the wave peak and, the average ratio of this maximum velocity to wave celerity is 0.96. However, when the wave asymmetry is strong, the maximum horizontal velocity of water particles occu  相似文献   

台湾海峡西部海域沉积物中六种金属氧化物的含量分布     

黄衍宽  曾 《台湾海峡》1988,(4)

据1985年台湾海峡西部海域综合调查资料,报道了该海域表层沉积物中MnO,MgO,Fe_2O_3,Al_2O_3,CaO和TiO_2的含量分布特征,讨论了各金属氧化物之间及其与沉积物类型的关系。  相似文献   

Control of Vortex Shedding at Moderate Reynolds Numbers   总被引：1，自引：0，他引：1  

SHAO  Chuanping 《中国海洋工程》2002,16(1):61-68

The suppression method of vortex shedding from a circular cylinder has been studied experimentally in the Reynolds number range from 300 to 1600. The test is performed in a water channel. The model cylinder is 1 cm in diameter and 38 cm in length. A row of small rods of 0.18 cm in diameter and 1 .5 cm in length are perpendicularly connected to the surface of the model cylinder and distributed along the meridian. The distance between the neighboring rods and the angle of attack of the rods can be changed so that the suppression effect on vortex shedding can be adjusted. The results show that vortex shedding can be suppressed effectively if the distance betvveen the neighboring rods is smaller than 3 times and the cylinder diameter and the angle of attack is in the range of 30°≤β < 90°  相似文献