共查询到20条相似文献，搜索用时 15 毫秒
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海上石油开发油井建设中，发生了井柱弯折现象。对工程处理中可以采用的小沉箱、大沉井、定向井、人工切割开洞等方案进行了介绍和比较，最后论述了采用的方案及原因。 相似文献
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Jeremy D. Duschenes Timothy W. Barash Paul J. Mattaboni Sean C. Solomon 《Marine Geophysical Researches》1981,4(4):437-450
We describe a recent modification to the MIT Ocean Bottom Seismometer by which the geophones are housed in a separate package that is deployed on the sea floor about 1 m distance from the main unit several hours after the OBS reaches the ocean bottom. Records from deep-sea experiments and shallow-water tests show two improvements over records from geophones housed in the main instrument package. Signals recorded by the external geophones have a much better signal-to-noise ratio because tape recorder noise and instrument vibrations generated by water currents are effectively eliminated. As a result, the overall frequency response of the sensors to ground motion has a demonstrably smoother spectral shape. The second improvement is that the cross coupling of horizontal instrument motion to vertical ground motion is apparently greatly reduced because of the simpler design for the sensor package. 相似文献
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P. Choukroune J. Francheteau B. Auvray J. M. Auzende J. P. Brun B. Sichler F. Arthaud J. C. Lepine 《Marine Geophysical Researches》1988,9(2):147-163
The results of 26 dives with the diving saucer Cyana in the Gulf of Tadjoura and Ghoubbet al Kharab (Republic of Djibouti) are presented. One can demonstrate that the sites of recent volcanism, tectonics and hydrothermal activity within the axial part of the Gulf of Tadjoura coincide with topographic highs trending at a high angle (azimuth 135°) with respect to the average trend of the axial trough of the Gulf (azimuth 080°). The highs owe their relief to both volcanism and normal faulting along a trend of 130–140°. Recent faulting on the bounding walls of the axial trough is also found along a trend of 130–140° where the faults interfere with another set of apparently older faults trending 070° parallel to the axial trough. Spacing between the active zones of the Gulf is regular and about 30 km. No evidence for transform faulting has been found, in contradiction to all previous kinematic models of the Gulf of Tadjoura. There is evidence that the presently active phase of opening associated with 130–140° faults is less than 0.7 my old and that there was an older phase associated with 070°–080° faults creating the main trough of the Gulf. The basaltic lavas created during the two phases have evolved from transitional to tholeiitic. 相似文献
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Nonlinear path-following control of an AUV 总被引：3，自引：0，他引：3
A new type of control law is developed to steer an autonomous underwater vehicle (AUV) along a desired path. The methodology adopted for path-following deals explicitly with vehicle dynamics. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path-following control strategies described in the literature. Controller design builds on Lyapunov theory and backstepping techniques. The resulting nonlinear feedback control law yields convergence of the path-following error trajectory to zero. Simulation results illustrate the performance of the control system proposed. 相似文献
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AQUA is an underwater hexapod robot that uses its paddles to propel itself and control its orientation. To aid in the vehicle development, a simulation was needed to predict the motion of the robot based on its paddle oscillations. The most difficult aspect of this simulation was the characterization of the forces generated by the paddles oscillating in the water. In this work, a model predicting the forces produced by an oscillating rigid paddle was developed and validated experimentally. Tests were performed on an experimental setup, which was designed and built to measure the forces and torques produced by a paddle oscillating in a water tank. Also, the forces produced by a flexible fin were determined experimentally and were compared to those generated by the rigid paddle. Finally, a simulation of the AQUA robot was developed, based on the validated rigid paddle model. 相似文献
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Robust diving control of an AUV 总被引：1，自引：0，他引：1
Lionel Lapierre 《Ocean Engineering》2009,36(1):92-104
Mobile systems traveling through a complex environment present major difficulties in determining accurate dynamic models. Autonomous underwater vehicle motion in ocean conditions requires investigation of new control solutions that guarantee robustness against external parameter uncertainty. A diving-control design, based on Lyapunov theory and back-stepping techniques, is proposed and verified. Using adaptive and switching schemes, the control system is able to meet the required robustness. The results of the control system are theoretically proven and simulations are developed to demonstrate the performance of the solutions proposed. 相似文献
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棉兰老岛以东反气旋涡的Argo观测研究 总被引：1，自引：0，他引：1
报道了2003年1月至10月期间,由布放于西北太平洋中的Argo剖面浮标捕获的位于棉兰老岛以东海域的反气旋涡。该涡中心位于8.7°N、127.6°E附近,距大陆坡不远,沿等深线走向呈椭圆形分布。其长轴(NW-SE)约200km,短轴(NE-SW)长约120km。Argo浮标的漂移轨迹及其在表层及1 500db层的漂移速度场表明,该反气旋涡位于温跃层以下,中层海洋特征。在1 500db层上,涡的外围平均切向速度为11.9—14.0cm.s-1,旋转周期约为40d。温、盐度断面分布表明,该反气旋涡内的温盐结构非常复杂,可能与源自南、北半球的中层水团在涡旋内交汇并发生变性有关。 相似文献
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为了验证波谱仪反演二维海浪谱的功能,根据海浪波谱仪的信号形成机制,总结了机载波谱仪反演海浪的流程。利用机载波谱仪回波数据,通过自相关和互相关两种功率谱估计方法,反演了二维海浪谱。最后通过与浮标测量的二维海浪谱进行对比,验证了该机载波谱仪探测二维海浪谱的有效性。结果表明,无论采用自相关函数还是互相关函数进行功率谱估计,得到的主波波长和有效波高与实际二维海浪谱基本一致。互相关函数法得到的交叉谱能去除180°模糊现象,其在计算有效波高时相对于自相关函数会稍微偏小。在计算斜率方差时可以采用5°~12°入射角范围的后向散射系数进行公式拟合,因此定标与否并不影响最后的二维海浪谱结果,未来星载波谱仪只有靠多波束联合才能实现。 相似文献
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Pan-Mook Lee Bong-Huan Jun Kihun Kim Jihong Lee Aoki T. Hyakudome T. 《Oceanic Engineering, IEEE Journal of》2007,32(2):327-345
This paper presents an integrated navigation system for underwater vehicles to improve the performance of a conventional inertial acoustic navigation system by introducing range measurement. The integrated navigation system is based on a strapdown inertial navigation system (SDINS) accompanying range sensor, Doppler velocity log (DVL), magnetic compass, and depth sensor. Two measurement models of the range sensor are derived and augmented to the inertial acoustic navigation system, respectively. A multirate extended Kalman filter (EKF) is adopted to propagate the error covariance with the inertial sensors, where the filter updates the measurement errors and the error covariance and corrects the system states when the external measurements are available. This paper demonstrates the improvement on the robustness and convergence of the integrated navigation system with range aiding (RA). This paper used experimental data obtained from a rotating arm test with a fish model to simulate the navigational performance. Strong points of the navigation system are the elimination of initial position errors and the robustness on the dropout of acoustic signals. The convergence speed and conditions of the initial error removal are examined with Monte Carlo simulation. In addition, numerical simulations are conducted with the six-degrees-of-freedom (6-DOF) equations of motion of an autonomous underwater vehicle (AUV) in a boustrophedon survey mode to illustrate the effectiveness of the integrated navigation system. 相似文献
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Variations in the mineralogy and chemistry of the shells of the filter-feeding organism Mytilus edulis have allowed discrimination of subenvironments of growth within the Tay estuary. Aragonite proportions higher than those predictable for the temperate, tidal, growth conditions are associated with stretches of the estuary affected by organic pollution. Accumulation and concentration of copper (Cu) in the organic periostracum suggest that Mytilus shell may also prove useful as a monitor of metallic element pollution.The relatively fragile nature of the polylayer shell of Mytilus and the layer specific distribution of components require the use of either complete, undamaged specimens or population groups to discriminate significant variations. 相似文献
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The paper studies longitudinal vibrations of an ultra-deepwater drilling riser whose bottom end is disconnected from the sea floor and covered by a plug (a blind one or the one with a hole). An elastic shell is used as a model of a riser pipe. The fluid column motion in the riser is described by the Navier–Stokes equation for a compressible fluid. Losses of fluid pressure during its flowing through a hole in the plug are taken into account. Solution of the riser equations is carried out in the frequency domain. Analysis of the effect which the riser length, wave period and height, and the plug-hole diameter on the amplitude of the riser's tension vibrations is conducted. A riser manufactured of strong aluminium alloys, some of prospective materials for ultra deepwater drilling, was considered as a prototype. It has been shown that risers 2000–4000 m long, plug-hole, and a riser 6000 m long with plug-hole of 0.087 m in diameter can withstand wave height of >15 m throughout the frequency range. 相似文献
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The hydrodynamic functioning of an oscillating water column (OWC) in the presence of an underwater tri-dimensional mound (UTDM) through large-scale ocean engineering basin experiments is described. Experiments are carried out with both regular and irregular waves and are compared to numerical models. The analysis is based on the measurements of the wave amplification in the water column for the OWC performance and on surface deformation upwave and over the UTDM for the wave transformation due to both UTDM and OWC. A significant increase of the capture-width ratio due to wave focusing above the mound is observed experimentally. This wave focusing is also well described numerically with a refraction–diffraction model. The wave amplification in the water column for both regular and irregular waves is compared to results from a linear potential model based on an integral matching method. Linear behaviour of the hydrodynamic response of the device is verified for both open and partially closed conditions, in particular for irregular waves. 相似文献
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Long-term data sets are discussed for three locations – a southern North Sea location, where sea states are typically dominated by wind-sea conditions, a Northwest Shelf of Australia location, where sea states are often a mix of wind-sea and swell conditions, and a Guinea Gulf location offshore Nigeria, where sea states are dominated by swell. Various types of sea state statistics that have application to availability studies are presented; but databases of these type that also include wind and current data can also be used to estimate response parameters, which can give a more direct assessment of availability, and some example statistics of these are also given. Finally, the availability of offloading an FLNG barge to carrier is evaluated for each of the data sets, for specific operability criteria. Two types of operability criteria are used in the availability evaluations, and the results compared. 相似文献
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In this paper, vortex-induced vibrations (VIV) of an elastically mounted sphere with two linear degrees of freedom have been experimentally studied. The dynamic response analysis shows that, for the range of reduced velocity from 2 to 14 here investigated, the sphere exhibits similar amplitudes and frequencies compared to the tethered sphere, and Modes I and II are detected. A new application of the phase average approach allowed extrapolating the periodic trajectory pattern from the experimental trajectories. In particular, more than one dominant harmonic component is observed in the streamwise oscillation, so the sphere trajectories are significantly different from the traditional figure-of-eight shape. The main difference is that these trajectories are not self-intersecting. Based on the experimental observations, an analytical model of the trajectory is built and discussed. 相似文献
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Robust Nonlinear Path-Following Control of an AUV 总被引：3，自引：0，他引：3
《Oceanic Engineering, IEEE Journal of》2008,33(2):89-102