Liu, Quangang (China Offshore Oil Engineering (Qingdao) Co. Ltd.) | Jiang, Liqun (China Offshore Oil Engineering (Qingdao) Co. Ltd.) | Yang, Fengyan (China Offshore Oil Engineering (Qingdao) Co. Ltd.) | Wang, Yongzhao (China Offshore Oil Engineering (Qingdao) Co. Ltd.) | Yan, Qingbo (China Offshore Oil Engineering (Qingdao) Co. Ltd.)
As the deepwater jackets are normally taller than ordinary jackets, most of them are built in the way of lay-down construction. The single panel is an elementary unit of a jacket, composed of horizontal single panel or vertical single panel. This paper introduces a lifting method for different single panels of deepwater jacket, considering various factors such as primary standing position of cranes, the cranes route, cranes capability, level lift and turnover lift, and other crucial elements in lifting process. Padeye lifting and sling hauling are two patterns in the lifting process, consisting of pipe padeyes and anti-slipping sling columns.
Dynamic thermodynamic calculation data of sea ice thickness since 1947 to 1996 in Chengdao oilfield is applied here to calculate corresponding design ice thickness. The fitting curves for these observations are selected from Gumbel, Weibull, lognormal, Pearson type-3 and maximum entropy distribution. Corresponding return values given by these curves are regarded as the best design sea ice thickness parameters. Based on distribution fitting tests and comprehensive consideration, lognormal distribution is chosen as the best fitting curve of annual extreme data for sea ice thickness conclusively. Then different return values can be deduced under different return periods, and maximum likelihood method is applied to determine interval estimations of these return values. The calculated results can provide a reference for disaster prevention and offshore structures design.
In Froude-scaled model tests of floating wind turbines, if the Reynolds number is higher than the critical Reynolds number, the scale effect can be neglected. In this paper, seven scale factors (1:100, 1:50, 1:30, 1:20, 1:15, 1:10 and 1:3) were used to calculate the rotor thrust coefficients of the NREL offshore 5-MW baseline wind turbine model blades. XFOIL software was used to analyze the lift and drag coefficient curves of the six airfoils. The thrust coefficients were obtained and compared with those of the prototype applying the Blade Element Momentum Theory. It can be concluded that the critical Reynolds number is approximately 2×105 (with a scale factor of 1:15). Lower Reynolds number model blades will show unfavorable aerodynamic performance in the model test.
Liu, Xincheng (Pan Shanghai Water Engineering Design & Research Institute Co.Ltd) | Du, Xiaotao (Pan Shanghai Water Engineering Design & Research Institute Co.Ltd) | Lu, Yongjin (Pan Shanghai Water Engineering Design & Research Institute Co.Ltd) | Pan, Lihong (Pan Shanghai Water Engineering Design & Research Institute Co.Ltd)
Shanghai is the most important coastal city in eastern China, the main area that will be influenced by the north pacific tropical cyclones. To protect the city from direct invasion of storm surge, 532 km seawalls have been built along the Changjiang Estuary and Hangzhou Bay area. They are the first promising barrier to Shanghai's safety from tidal flood. Currently, the standard for the dike design in Shanghai is mainly of 200 years return period in tide level combined with force 12 wind, with the world climate change and frequent severe weather, the safety of dike structure under the excessive storm surge, if happens, is the most concern by city managers. A 7.0km long dike at the junction of Changjiang Esutary and Hangzhou Bay is chosen to be studied here. A typhoon route which may have negative effect on the dike is given after some numerical simulation. By using storm surge model and typhoon- generate wave model, tide level before dike, wave force and wind speed are calculated under the conditions of severe typhoon (40 m/s at center) and super typhoon (60 m/s at center) with the selected route. According to the tide level and wave conditions of these excessive storm surge in the seawall of Lingang, the feature of armored structure, seawall stability and anti-scouring ability of back-slope from overtopping are studied.
The result shows, the No. 9711 typhoon route with a 1.5 degree latitude translation to the north will be the most harmful to the research area and two different typhoon intensities are set on this rout, separately the intensity equal to No. 9711 as severe typhoon and No. 5612 as super typhoon. Under the condition of severe typhoon, the highest tidal level can be 6.74 m (Shanghai Wusong Datum) and the average wave height be 2.99 m, with the condition of super typhoon separately be 7.68m and 3.50 m.
Under the severe typhoon, the fence board thickness on current seawall, single wing shape block weight and the overall anti-slipping are all satisfy the stability condition, but the anti overturning stability is dissatisfy, and wave overtopping exceed to the normal extent, as a result the back-slope can easily be scoured.
Under the super typhoon, fence board thickness approaches to critical number, other indicator such as single block weight, anti-slipping, anti-overturning are all dissatisfy the stability condition. Also, the overtopping extremely beyond the normal extent and the back-slope can be easily scoured.
In this paper, we also present some advanced advice to deal with excessive typhoon.
We aim to analyse the extreme hydraulic environment in Bohai Sea in case of cold wave. According to the historical statistics of cold wave hitting Bohai Sea, three typical paths with four different wind speeds for each are chosen for the numerical simulation. Then, by means of Princeton Ocean Model (POM), we simulate the cold wave in Bohai Sea. In particular, nest calculations are conducted for Puti Island wind farm in Bohai Sea in order to manifest the extreme hydrodynamics in the area of the planned wind farm project.
The hydrodynamic characteristics of propeller are investigated widely due to the great significance of ship propulsion performance. In this paper, the hydrodynamic performance of DTMB P4119 propeller with viscous flow is studied by the MRFSimpleFoam solver based on the open-source computation platform OpenFOAM. The open-water characteristics in different advance coefficient (J 0.5, 0.7, 0.833, 0.9) have been computed and compared with the experimental results which show good consistency. The pressure coefficient distribution at different cross sections is analyzed to show the forces of blade surface. The detailed wake flow field, such as the wake vortex structure and streamline around the blade, has also been analyzed to strengthen the perception and cognition about the hydrodynamic performance of this propeller. The results show that this solver provides an effective tool to simulate the hydrodynamic performance of propeller and analyze the detailed flow structure in viscous flow. It has prospect to study more complex flow phenomena and unconventional propeller.
Unsteady hydroelastic waves generated by impulsively-starting surface and submerged concentrated loads in a fluid with an underlying uniform current are studied analytically. The fluid is assumed to be homogeneous, incompressible, inviscid, and of finite depth. For the case of irrotational motion with small-amplitude deflections, linear potential-flow theory is employed. The Laplace equation is the governing equation, with the dynamic condition representing a balance among the hydrodynamic, elastic, inertial forces and the downward applied load. It is shown that the analytical solution, obtained by the Laplace–Fourier integral transform, consists of steady-state and transient responses. For the steady response, an explicit expression is further derived by the residue theorem, while the transient response is obtained by the stationary-phase method. These expressions allow the effects of various physical parameters on the hydroelastic responses to be studied in detail. It is found that the flexural–gravity wave motion depends on the ratio of current speed to phase or group speeds.
Zhang, Y. (Shanghai Jiao Tong University, Shanghai) | Jeng, D-S (Griffith University Gold Coast Campus) | Liao, C.C. (Griffith University Gold Coast Campus) | Zhao, H.Y. (Shanghai Jiao Tong University, Shanghai) | Zhang, J.S. (Griffith University Gold Coast Campus)
This paper presents an integrated model for the wave(current)-induced seabed response. The Reynolds-Averaged Navier-Stokers (RANS) Equations and k-ε turbulence model are applied in the fluid field and the poro-elastoplastic model is used to simulate the seabed response. Validation of the present integrated model is presented first. Then the effect of currents on the seabed response is examined by considering both the oscillatory and residual mechanisms of the pore pressure inside the soil. A parametric study is conducted to examine the characteristics of the poro-elastoplastic model here. It shows that the development of the two-dimensional liquefaction zone can be illustrated by the present model. Besides, results show that opposite direction between waves and currents yields faster liquefaction process compared to the same direction.
Due to dispersive errors, numerical dissipation of the advection terms may have a great influence on numerical solution accuracy of advection-diffusion issue. It is necessary to grasp numerical dissipation level before putting some scheme into use. Considering the lack of quantitative indicator on numerical dissipation, the quantitative indicator and research method were established in this paper. The method was successfully used to study the false diffusion law of QUICKEST discrete scheme and guild how to choose an appropriate discrete scheme in numerical simulation of salinity of Yangtze river estuary.
The results show that the false diffusion coefficient could be applied to characterize the numerical dissipation level. The value of the false diffusion coefficient can be obtained according to the true dispersion effect.
In this paper, we proposed a three-dimensional model for the tension analysis of submarine power cables during laying operations. Both flexural rigidity and axial elasticity were taken into consideration in the form of classical Euler-Bernoulli beam element theory. The governing equations were numerically solved by fourth-order Runge-Kutta methods and the derivatives of the curvature with respect to the cable element arc length can be approximately expressed by the finite difference method. Numerical examples were illustrated to study the influence of some key parameters on the cables and some significant conclusions are drawn.