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111.
On the use of the capability polar plots program for dynamic positioning systems for marine vessels 总被引:2,自引:0,他引:2
As the capability of polar plots becomes better understood, improved dynamic positioning (DP) systems are possible since the control algorithms greatly depend on the accuracy of the aerodynamic and hydrodynamic models. The measurements and estimation of the environmental disturbances have an important role in the optimal design and selection of a DP system for a marine vessel. The main objective of this work is to present a new software program capable of estimating the environmental forces, thrusters capability calculations, and capability polar plots for marine vessels. A flowchart illustrating the logic and data flow of a developed software program, the Capability Polar Plot Program (CPPP), and the estimated results for two case studies for a scientific drilling vessel and a survey vessel are presented. It is obvious from the obtained results that the developed program has a future potential for the estimation of the Capability Polar Plots for marine vessels. Moreover, the developed software program would be considered as a marine tool for the thrusters' selection and their configuration for marine vessels and floating production units for the Oil and Gas industries. 相似文献
112.
我国的海带养殖是海水养殖业的支柱产业之一 ,是世界上海藻养殖业中规模最大的产业,其养殖产量连续多年居世界首位,目前年产量已达600000t多干品[2]。我国生产的海带除了大部分作为食品食用外 ,还有部分作为工业原料,提取褐藻胶、褐藻淀粉、甘露醇、碘、氯化钾等产品。我国褐藻胶年产量已达15000t,在生产过程中产生大量的漂浮渣,都把其当作废物排放掉,这样不仅污染了环境 ,而且造成了资源的大量浪费。为了进一步地综合利用海带资源,变废为宝 ,作者对青岛某一褐藻胶厂排放的漂浮渣进行了较深入的化学成分分析。现报道利用气… 相似文献
113.
The dynamics of multiple floating structures have been studied using the finite element method. The emphasis is on the hydrodynamic behaviour of multiple bodies under a multi-directional wave field. A two-dimensional numerical model has been adopted to evaluate hydrodynamic coefficients and forces in an oblique wave field. The responses in sway, heave and roll modes are reported. The linear filter technique is then used to extrapolate the responses under directional waves. The effect of mean wave direction and directional homogeneity on the hydrodynamic behaviour of the structure is studied. Based on the present study, it is found that the two-dimensional model is applicable to investigate the wave-structure interaction problems of the type herein considered. 相似文献
114.
利用求补色立体图屏幕坐标原理,采用浮动水平线法来绘出空间曲面的透视投影图形。通过参数变换可展示出不同视点、不同视角、不同视距下物体表面的形态,通过双眼视觉加强所展示物体表面的真实感。实验表明,该方法有广泛的应用价值。 相似文献
115.
Spreading of floating particles by Langmuir circulation 总被引:1,自引:0,他引:1
S.A. Thorpe 《Marine pollution bulletin》2009,58(12):1787-1791
Particles floating on the sea surface, in particular buoyant algae, are drawn into bands by the converging flow between neighbouring Langmuir cells. Floating bands subsequently amalgamate as a result of Langmuir turbulence. Simple models are developed to describe the rearrangement and dispersion of the floating particles. If the production of floating particles has ceased, the mean separation of the bands of particles increases with time and eventually becomes unrelated to the mean distance between the lines of convergence resulting from Langmuir circulation. The concentration of particles in the bands, proportional to the width of bands, and the separation of bands with a given concentration of particles, both increase with time. Care is needed in estimating the width of Langmuir cells to distinguish between surface bands of floating material that is continuously being produced and bands made visible by some earlier, but discontinued, generation. An alternative mechanism for the generation of dense bands of floating algae is proposed. 相似文献
116.
Based on the linear potential flow theory and matching eigen-function expansion technique, an analytical model is developed to investigate the hydrodynamics of two-dimensional dual-pontoon floating breakwaters that also work as oscillating buoy wave energy converters (referred to as the integrated system hereafter). The pontoons are constrained to heave motion independently and the linear power take-off damping is used to calculate the absorbed power. The proposed model is verified by using the energy conservation principle. The effects of the geometrical parameters on the hydrodynamic properties of the integrated system, including the reflection and transmission coefficients and CWR (capture width ratio, which is defined as the ratio of absorbed wave power to the incident wave power in the device width). It is found that the natural frequency of the heave motion and the spacing of the two pontoons are the critical factors affecting the performance of the integrated system. The comparison between the results of the dual-pontoon breakwater and those of the single-pontoon breakwater shows that the effective frequency range (for condition of transmission coefficient KT < 0.5 and the total capture width ratio ηtotal > 20%) of the dual-pontoon system is broader than that of the single-pontoon system with the same total volume. For the two-pontoon system, the effective frequency range can be broadened by decreasing the draft of the front pontoon within certain range. 相似文献
117.
118.
In order to predict the roll motion of a floating structure in irregular waves accurately, it is crucial to estimate the unknown damping coefficients and restoring moment coefficients in the nonlinear roll motion equation. In this paper, a parameter identification method based on a combination of random decrement technique and support vector regression (SVR) is proposed to identify the coefficients in the roll motion equation of a floating structure by using the measured roll response in irregular waves. Case studies based on the simulation data and model test data respectively are designed to validate the applicability and validity of the identification method. Firstly, the roll motion of a vessel is simulated by using the known coefficients from literature, and the simulated data are used to identify the coefficients in the roll motion equation. The identified coefficients are compared with the known values to validate the applicability of the identification method. Then the roll motion is predicted by using the identified coefficients. The prediction results are compared with the simulated data, and good agreement is achieved. Secondly, the model test data of a FPSO are used to identify the coefficients in the roll motion equation. Then the random decrement signature of the roll motion is predicted by using the identified coefficients and compared with that obtained from the model test data, and satisfactory agreement is achieved. From this study, it is shown that the identification method can be effectively applied to identify the coefficients in the nonlinear roll motion equation in irregular waves. 相似文献
119.