共查询到20条相似文献,搜索用时 0 毫秒
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An analytical theory is developed to study the effects of a coaxial tube-sector-shaped supporting structure on the conversion efficiency of a suspended, circular OWC converter. An eigen-function expansion method is employed in a cylindrical coordinate system to study wave interaction with an OWC converter in finite depth of water. Effects of the supporting structure, OWC dimensions, wave direction on energy conversion efficiency, and optimization of power-takeoff devices are discussed. Our results show that the coaxial tube-sector-shaped support with an opening in the range of π/2–5π/4 can significantly increase the conversion efficiency and widen the frequency range over which the conversion efficiency is high. 相似文献
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中国科学院海洋研究所在开展西太平洋马里亚纳海山区多学科综合科学考察的过程中,利用"科学"轮船载的全水深多波束测深系统Seabeam3012对多个海山进行了地形测量工作。针对作业过程中遇到的恶劣海况导致采集数据质量差、多波束系统易检测错误海底信息、测线布设难度大等问题,提出了基于船体姿态对数据质量影响分析的多波束测线方向优化、基于地形变化并参考浅地层剖面资料的作业参数优化和基于实时采集情况的多波束采集测线布设优化等一系列措施,有效地提高了海山区多波束数据采集质量,并提高了作业效率。获得的高品质地形数据,为多学科协同研究奠定了基础,为ROV等设备的现场作业提供了安全保障。 相似文献
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Gridding heterogeneous bathymetric data sets with stacked continuous curvature splines in tension 总被引:3,自引:0,他引:3
Gridding heterogeneous bathymetric data sets for the compilation of Digital bathymetric models (DBMs), poses specific problems
when there are extreme variations in source data density. This requires gridding routines capable of subsampling high-resolution
source data while preserving as much as possible of the small details, at the same time as interpolating in areas with sparse
data without generating gridding artifacts. A frequently used gridding method generalizes bicubic spline interpolation and
is known as continuous curvature splines in tension. This method is further enhanced in this article in order to specifically
handle heterogeneous bathymetric source data. Our method constructs the final grid through stacking several surfaces of different
resolutions, each generated using the splines in tension algorithm. With this approach, the gridding resolution is locally
adjusted to the density of the source data set: Areas with high-resolution data are gridded at higher resolution than areas
with sparse source data. In comparison with some of the most widely used gridding methods, our approach yields superior DBMs
based on heterogeneous bathymetric data sets with regard to preserving small bathymetric details in the high-resolution source
data, while minimizing interpolation artifacts in the sparsely data constrained regions. Common problems such as artifacts
from ship tracklines are suppressed. Even if our stacked continuous curvature splines in tension gridding algorithm has been
specifically designed to construct DBMs from heterogeneous bathymetric source data, it may be used to compile regular grids
from other geoscientific measurements. 相似文献
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数值水槽内的阻尼消波和波浪变形计算 总被引:8,自引:3,他引:8
采用时域内对波面运动位置追踪的边界元方法,建立了一种非线性波浪变形计算的三维数值模式,并借助Spongelayer阻尼消波和Sommerfeld放射条件相匹配的处理方式,开发了一条三维非线性波的数值造波水槽,进而对水槽内的Stokes波进行了波浪变形计算。 相似文献
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Wave dissipation by vegetation with layer schematization in SWAN 总被引:1,自引:0,他引:1
Tomohiro Suzuki Marcel ZijlemaBastiaan Burger Martijn C. MeijerSiddharth Narayan 《Coastal Engineering》2012,59(1):64-71
The energy of waves propagating through vegetation is dissipated due to the work done by the waves on the vegetation. Dalrymple et al. (1984) estimated wave dissipation by integrating the force on a cylinder over its vertical extent. This was extended by Mendez and Losada (2004) to include varying depths and the effects of wave damping due to vegetation and wave breaking for narrow-banded random waves. This paper describes the wave dissipation over a vegetation field by the implementation of the Mendez and Losada formulation in a full spectrum model SWAN, with an extension to include a vertical layer schematization for the vegetation. The present model is validated with the original equation and results from Mendez and Losada (2004). The sensitivity of the model to the shape of the frequency spectrum, directional spreading and layer schematization are investigated. The model is then applied to field measurements by using a vegetation factor. This model has the ability to calculate two-dimensional wave dissipation over a vegetation field including some important aspects such as breaking and diffraction as used in SWAN model. 相似文献
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Norbert J. Schulz Robert S. Detrick Stephen P. Miller 《Marine Geophysical Researches》1988,10(1-2):41-57
Magnetic data collected in conjunction with a Sea Beam bathymetric survey of the Mid-Atlantic Ridge south of the Kane Fracture
Zone are used to constrain the spreading history of this area over the past 3 Ma. Two-dimensional forward modeling and inversion
techniques are carried out, as well as a full three-dimensional inversion of the anomaly field along a 90-km-long section
of the rift valley. Our results indicate that this portion of the Mid-Atlantic Ridge, known as the MARK area, consists of
two distinct spreading cells separated by a small, zero-offset transform or discordant zone near 23°10′ N, The youngest crust
in the median valley is characterized by a series of distinct magnetization highs which coalesce to form two NNE-trending
bands of high magnetization, one on the northern ridge segment which coincides with a large constructional volcanic ridge,
and one along the southern ridge segment that is associated with a string of small axial volcanos. These two magnetization
highs overlap between 23° N and 23°10° N forming a non-transform offset that may be a slow spreading ridge analogue of the
small ridge axis discontinuities found on the East Pacific Rise. The crustal magnetizations in this overlap zone are generally
low, although an anomalous, ESE-trending magnetization high of unknown origin is also present in this area. The present-day
segmentation of spreading in the MARK area was inherited from an earlier ridge-transform-ridge geometry through a series of
small (∼ 10 km) eastward ridge jumps. These small ridge jumps were caused by a relocation of the neovolcanic zone within the
median valley and have resulted in an overall pattern of asymmetric spreading with faster rates to the west (14 mm yr−1) than to the east (11 mm yr−1). Although the detailed magnetic survey described in this paper extends out to only 3 Ma old crust, a regional compilation
of magnetic data from this area by Schoutenet al. (1985) indicates that the relative positions and dimensions of the spreading cells, and the pattern of asymmetric spreading
seen in the MARK area during the past 3 Ma, have characterized this part of the Mid-Atlantic Ridge for at least the past 36
Ma. 相似文献
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LIU Dian-yong 《中国海洋工程》2021,(1):61-71
Extreme wave is highly nonlinear and may occur due to diverse reasons unexpectedly.The simulated results of extreme wave based on wave focusing,which were generated using high order spectrum method,are presented.The influences of the steepness,frequency bandwidth as well as frequency spectrum on focusing position shift were examined,showing that they can affect the wave focusing significantly.Hence,controlled accurate generation of extreme wave at a predefined position in wave flume is a difficult but important task.In this paper,an iterative adaptive approach is applied using linear dispersion theory to optimize the control signal of the wavemaker.The performance of the proposed approach is numerically investigated for a wide variety of scenarios.The results demonstrate that this approach can reproduce accurate wave focusing effectively. 相似文献
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We study horizontal wave currents generated in a liquid of finite depth by a load of constant intensity moving over the floating ice cover and analyze the dependences of the space structure of the field of wave velocities on the characteristics of the ice cover and the velocity of motion of the load. It is shown that the velocity of wave currents caused by flexural waves can increase with the velocity of motion of the load, whereas the wave currents caused by the gravity waves decay monotonically. The ice compression increases the velocity of horizontal wave currents. 相似文献
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海底地形对开展海洋科学调查和研究十分重要。以多波束为主的回声测深技术测量成本高且效率低,几十年来仅实现了全球约20%的海床测绘。对于空白区(特别是深海区域),可以借助重力异常和重力垂直梯度异常进行回归分析反演得到,但该方法得到的比例因子鲁棒性不强。为了解决这一问题,同时考虑到两种重力数据在表征海底地形长短波长的不同优势,本文结合滑动窗口赋权和稳健回归分析来反演海底地形。在太平洋皇帝山海域(35°~45°N,165°~175°E)的实验结果表明:在船测检核点处,本文构建模型的标准差为61.02 m,相比于单一重力数据反演模型,精度分别提高了14.92%(重力异常)和2.08%(重力垂直梯度异常),能较好地反映皇帝海山链的地形走势。 相似文献
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Anthony N. Williams 《Ocean Engineering》1985,12(1):25-43
The scattering of waves by both floating and submerged stationary elliptical breakwaters is investigated by means of linearised shallow water wave theory. This formulation leads to solutions for the fluid velocity potential in terms of Mathieu functions of real argument. Expressions are derived for the wave-induced forces and moments on the structures and their total and differential scattering cross-sections. Numerical results are presented for a range of wave and structural parameters.The present analysis serves as a prelude to a more comprehensive study of the problem without the shallow water restriction. 相似文献
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Suction-induced seepage is pivotal to the installation of caisson foundations in sand. Indeed, the upward pore water flow on the inner side of the caisson wall causes a release of a fraction of soil resistance due to the reduction of the lateral effective stress. A safe caisson installation requires a reliable prediction of soil conditions, especially soil resistance and critical suction for piping. These soil conditions must be predicted for the whole installation process.In this paper, we examine the effect on such prediction of the assumed permeability profile, which is described as a function of depth below the mudline. This study is motivated by the fact that marine sediments generally exhibit a permeability that decreases with depth because of consolidation under gravity. Hence, the question is whether conventional theories based on a constant permeability lead to a conservative prediction of soil conditions or not. Our conclusion is affirmative only regarding piping condition. As for soil resistance, a prediction based on the assumption of a constant permeability is non-conservative. This is due to an overestimated reduction in effective stresses under suction-induced seepage. 相似文献
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Analysis of Wave Height in Front of a Wave Absorbing Structure with Rubble Foundation 总被引:1,自引:0,他引:1
Li Rongqing Xie Shileng Engineer The First Design Institute of Navigation Engineering The Ministry of Communications Tianjin Professor Senior Engineer Deputy Chief Engineer The First Design Institute of Navigation Engineering The Ministry of Communications Tianjin 《中国海洋工程》1992,(3)
Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed. 相似文献
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By applying the linear water wave theory and the eigenfunction expansion method, the wave reflection by a vertical wall with a horizontal submerged porous plate is investigated in this paper. The numerical results, concerning the effects of the dimensionless plate length, the relative water depth, and the porous effect parameter of the plate on the wave loads on the plate and the wave height near the wall as well as the reflection coefficient, are discussed. It is found that the submerged plate increases the complexity of the phenomenon related to the wave reflection and refraction in the close region of the wall, and leads to the occurrence of the phenomenon of wave trapping. The results indicate that there may exist a process of focusing wave energy near the wall for small dimensionless porous effect parameters, whereas the increase of the dimensionless porous effect parameter decreases gradually the wave height until setdown occurs. The behavior of a larger plate with proper porosity is similar to that of a wave absorber which can significantly suppress not only the wave height above the plate but also the reflection waves. The ability of the porous plate to reduce the wave height on the wall surface is, in general, directly proportional to the dimensionless plate length and may be strongest for a proper value of the dimensionless porous effect parameter. It is also demonstrated that the wave loads on a porous plate are smaller than those on an impermeable plate. 相似文献
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在势能流及微小振幅波理论假设下,采用复合边界元素法(CBEM)数值解析规则波通过单根外壁透水cosine-type型同心圆柱结构物绕射。将cosine-type外壁不透水条件改为透水外,并在内部设有一半径为b的不透水内圆柱共同组成同心圆柱,为了验证CBEM数值模式正确性与可行性,将其退化成圆柱,均得到合理结果。数值计算条件包含波浪正向入射凸端、透水参数及绕射参数,探讨波浪通过单根cosine-type同心圆柱体四周水面波动变化情况,并与双重圆筒同心圆柱作比较。计算结果显示结构物外壁采用透水型式,可以大幅降低cosine-type同心圆柱体四周整个波浪绕射场的水面波动。 相似文献
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The radiation problem for a deep submerged cylinder is analysed and an asymptotic expression, uniformly valid in the whole range of frequencies, is derived for the radiation damping and exciting force. The obtained expression is a natural extension of the inertia term in the well known Morison's formula and may be useful in the analysis of certain ocean structures such as a tension leg platform, for example. In particular it makes it possible to define a geometry tuned to have null excitation at some desired frequency. 相似文献
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Emin Demirbağ Hülya Kurt Doğa Düşünür Kerim Sarıkavak Suna Çetin 《Marine Geophysical Researches》2007,28(4):343-353
In this study we made a comparative interpretation of multibeam bathymetric and seismic reflection data with different resolutions
and penetration properties collected in the Central Basin of the Marmara Sea. Our main objectives were (i) to investigate
and compare the active tectonic deformation observed on the sea bottom and within the uppermost sedimentary layers to that
of the deep-seated deformation within the limits of resolution and penetration of the available geophysical data and (ii)
to build a three-dimensional (3D) block diagram of the active tectonic and buried features by means of a sliced mapping technique. In this approach, we produced slice maps of the active and buried structural features at selected depths and then combined
them to form a 3D structural block diagram. Motivation for our work was to produce a 3D structural diagram to derive a more
detailed image of the structural features in the Central Basin where there is no available 3D seismic data. The observations
from the bathymetry and seismic data and developed 3D diagram support the presence of a through-going strike-slip fault that
forms a rotational depression zone against a right-stepping strike-slip faulting causing a pull-apart basin in the Central
Depression zone. 相似文献