共查询到20条相似文献，搜索用时 31 毫秒
1.
L. D. Pukhtyar 《Physical Oceanography》1998,9(1):25-32
The paper addresses the theoretical problem of electromagnetic fields induced by surface and internal waves in a fluid with
continuously stratified electrical conductivity and density. Calculations of the electromagnetic fields induced by the wave
motion in the tropical Atlantic have been performed considering the exponentially changing electrical conductivity in the
vertical. The consideration of the electrical conductivity stratification is shown to be capable of modifying electromagnetic
fields in the individual fluid layers by about 50%, and the role of this stratification is shown to increase with the growth
of the wave period.
Translated by Vladimir A. Puchkin. 相似文献
2.
The paper examines so-called wave boundary layers arising in a bounded stratified fluid for large times. Each the layer is a narrow domain in the vicinity of the fluid surface and/or bottom characterized by sharp, growing with increasing time, vertical gradients of the buoyancy and horizontal velocity. The layers arise as a result of free linear wave evolution of the initial fields if the initial buoyancy at the boundaries depends on the horizontal coordinates. An asymptotic solution for the boundary layer for large times is presented, and it is shown that this solution describes exact fields fairly well even for moderate times. 相似文献
3.
V. P. Smagin S. V. Semkin V. N. Savchenko 《Izvestiya Atmospheric and Oceanic Physics》2013,49(5):541-547
The electric and magnetic field and electric charges at the medium interface induced by a two-dimensional marine surface and internal waves are considered. The influence of the magnetic permeability and electric conductivity of the bottom rocks on the induced fields is analyzed. 相似文献
4.
投弃式海流剖面测量仪测量原理研究 总被引：1，自引：0，他引：1
根据投弃式海流剖面测量仪的测量原理建立了二维海流运动感生电场离散和连续模型,通过模型推导得到了海流与感生电场间的关系公式。通过对海流感生电磁场的分析,对海流测量的基本方法进行了研究,通过感生电磁场的量级的计算,确定了投弃式海流剖面测量仪研究的主要方向和关键技术。 相似文献
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An exact, analytical solution is obtained for the title problem which constitutes a classical one although no solution is available in well known textbooks and handbooks normally used by the structural engineer in several fields of technology: ocean and naval engineering, aerospace applications, etc. The authors performed this study motivated by a situation where excessive displacements were noticed in a structural element carrying a relatively small motor at the free end and placed at the engine room of a naval vessel. The Bernoulli-Euler model has been employed. 相似文献
9.
Izvestiya, Atmospheric and Oceanic Physics - A stable analytical solution is obtained for wave fields of seismic waves in a planetary-sized sphere using the new asymptotic behavior of the Bessel... 相似文献
10.
界面波作用产生的周期沙波现象的动力机制一直没有得到合理圆满的解释。本文针对这种现象通过对浅水弱非线性Boussinesq方程,讨论界面波由于反射效应产生的反射波与入射波的非线性相互作用,得出了一个不受时间变量制约的不传播非线性二阶驻波解。从这个驻波解空间分布上可以看出,这种动力机制作用产生的周期沙波通常是其波形平行于反射壁,并且沙波波长为入射波垂直反射壁面分量的一半。数值模拟结果证明这个非线性二阶波是Genus-2波列的一个子集．水槽实验和海岸高空照片资料上清楚的分辨出这种由反射壁效应产生的沙波的客观存在性。 相似文献
11.
深水开发的新型立管系统——钢悬链线立管(SCR) 总被引：12，自引：0，他引：12
1种全新的深水立管系统——钢悬链线立管（Steel Catenary Riser，SCR）在翠西哥湾（Golf of Mexico）、坎普斯湾（Campos Basin）、北海（North Sea）和西非（West Africa）得到了成功应用。它的适用水深为300～3000m，且适用现有任何浮式结构，从浅水的固定式平台到极深水的浮式生产储运系统（FPSO）。因此，它取代了传统的柔性立管和顶张力立管，成为深水油气开发的首选立管，被认为是深水立管系统的成本有效的解决方案。 相似文献
12.
S. V. Semkin V. P. Smagin V. N. Savchenko 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):128-131
In this paper we study the inertial and induction mechanisms of electric-current generation in sea-water motions. The problem
of calculating the magnetic field induced by these currents is considered. For the induction generation mechanism, if self-induction
is disregarded, the fields arising in central-symmetric motions of sea water (like underwater explosions) are calculated. 相似文献
13.
Surface water waves in coastal waters are commonly modeled using the mild slope equation. One of the parameters in the coastal boundary condition for this equation is the direction at which waves approach a coast. Three published methods of estimating this direction are examined, and it is demonstrated that the wave fields obtained using these estimates deviate significantly from the corresponding analytic solution. A new method of estimating the direction of approaching waves is presented and it is shown that this method correctly reproduces the analytic solution. The ability of these methods to simulate waves in a rectangular harbor is examined. 相似文献
14.
Atmospheric frontal gravity waves observed in satellite SAR images of the Bohai Sea and Huanghai Sea 总被引：1，自引：0，他引：1
LIU Shuming LI Ziwei YANG Xiaofeng Pichel William G YU Yang ZHENG Quanan LI Xiaofeng 《海洋学报(英文版)》2010,29(5):35-43
In the satellite synthetic aperture radar (SAR) images of the Bohai Sea and Huanghai Sea, the authors observe sea surface imprints of wave-like patterns with an average wavelength of 3.8 km. Comparing SAR observations with sea surface wind fields and surface weather maps, the authors find that the occurrence of the wave-like phenomena is associated with the passing of atmospheric front. The authors define the waves as atmospheric frontal gravity waves. The dynamical parameters of the wave packets are derived from statistics of 9 satellite SAR images obtained from 2002 to 2008. A two-dimensional linear physical wave model is used to analyze the generation mechanism of the waves. The atmospheric frontal wave induced wind variation across the frontal wave packet is compared with wind retrievals from the SAR images. The CMOD-5 (C-band scatterometer ocean geophysical model function) is used for SAR wind retrievals VV (transmitted vertical and received vertical) for ENVISAT and HH (transmitted horizontally and received horizontally) for RADARSAT-1. A reasonable agreement between the analytical solution and the SAR observation is reached. This new SAR frontal wave observation adds to the school of SAR observations of sea surface imprints of AGWs including island lee waves, coastal lee waves, and upstream Atmospheric Gravity Waves (AGW). 相似文献
15.
海洋背景磁场模拟计算及东中国海表层磁场分布 总被引：1，自引：0，他引：1
海洋中海水的运动会切割地球磁场,生成微弱的电场,进而在海洋内部和周围空间激发感生电磁场,即约为地球磁场一万至十万分之一的微弱海洋背景磁场.文中针对海洋背景磁场的生成机制及近几十年来对海洋背景磁场的理论研究,结合世界磁场模型WMM2005,模拟计算了三种典型的海洋运动--海浪、海流、内波所产生的感应磁场,建立了海洋背景磁场的数值计算模型,并在此基础上设计开发了海洋背景磁场的模拟计算软件.最后用卫星多传感器资料驱动普林斯顿海洋动力学模式,得到的东中国海2005年海洋表层环流数据,模拟计算了东中国海海表层磁场分布,对其磁场变化与分布规律作了简要分析. 相似文献
16.
Estimation of boundary values in a North Atlantic circulation model using an adjoint method 总被引：2，自引：0，他引：2
A 1° × 1° resolution version of the MIT-GCM in the North Atlantic is used to test whether open-boundary conditions can be constrained by observations inside the domain using an adjoint method. In this preliminary feasibility study, the model is run during 1993 with a simplified vertical mixing physics. It is constrained by monthly SST fields, monthly climatological θ, S fields and TOPEX/POSEIDON altimetry. The adjoint model is built using automatic differentiation software. The method aims at bringing the model’s trajectory to consistency with data, by adjusting the initial θ, S fields, the time-varying atmospheric forcing fields and the time-varying open-boundary values. An originality of the work is the ‘nested approach’, which uses optimized fields from a global, coarser resolution model for the open-boundary conditions and for the prior estimates of the surface conditions adjustments. A solution is obtained after 75 iterations. This study shows that significant changes can be obtained on the open-boundary values, and that a general improvement in the circulation is achieved in the constrained solution, mainly in the Gulf Stream and equatorial regions. Changes at the open boundaries are characterized by a large temporal variability and small spatial scales. Large local adjustments are found close to the bottom and are likely unrealistic. There, the method tends to compensate for some model’s deficiencies by computing large corrections on the open-boundary values. The analysis of the cost function gradients with respect to the controls allows us to explore the local consistency between the constraints from the different data sets. This study suggests that no fundamental difficulty emerges when constraining open-boundary values. Its extension to a longer run with complete mixing physics can be envisaged. 相似文献
17.
The results of investigations of internal waves carried out in three test ranges located in the north part of the Aegean Sea and characterized by different dynamics of wave motions and water masses are used to study the electromagnetic waves induced by wave motions. We analyze their dependence on the period of waves and wavelength, reveal specific features of the behavior of the electric and magnetic fields and their phases as functions of depth, and compare the intensities of electromagnetic fields obtained under different hydrological conditions. 相似文献
18.
N. A. Palshin A. A. Nozdrina V. A. Matyushenko A. M. Porai-Koshits I. V. Egorov 《Oceanology》2006,46(3):325-334
A technique for studying near-shore currents is assessed that is alternative to the traditional methods. The technique is based on the measurements of anomalous electromagnetic fields induced on land in the near-shore zone. The method of coastal electromagnetic monitoring was tested in the central part of the Zimnii Coast of the Gorlo of the White Sea. The results of numerical modeling of electric fields induced by tidal currents allowed us to obtain theoretical estimates of the expected signal and to choose the site of the measurements and the optimal parameters of the receiving lines applied. The experimental studies were performed on the Zimnii Coast of the Gorlo of the White Sea using two horizontal receiving lines, one of which was located on the coast and the other ran in the sea. These studies provided experimental estimates of the electric field of the tides in the Gorlo of the White Sea, which agreed with the theoretical evaluations. The results of the studies proved the efficiency of the method of coastal electromagnetic monitoring, which may be used in order to study tidal, offset-onset (surge), and quasi-stationary currents. An important advantage of the electromagnetic methods lies in the possibility to perform the studies throughout the year, including the winter period. 相似文献
19.
The stability of the zonal axisymmetric quasi-geostrophic hydrostatic solution to the equations of atmospheric dynamics that is determined by the horizontal temperature gradient is studied. Time-dependent regions of unstable solutions specified by the Rayleigh number describe ordinary convective (baroclinic) processes and the long-term weak growth of disturbances under the action of the centrifugal forces arising from the Earth’s rotation. Comparison with a centrifugal hydrodynamic instability is made. The spatiotemporal structure of the corresponding geophysical fields is described. 相似文献
20.
Within the framework of the reduced-gravity model of the ocean taking into account the effect of friction in the Rayleigh form, we study the two-dimensional problem of nonlinear motions of a subsurface front of finite width. We consider the conservation laws and the character of motion of the center-of-mass of the cross section of the front and their variations caused by the losses of energy. For fields with special structure, the problem is reduced to the solution of a system of nonlinear ordinary differential equations. It is shown that the initially geostrophic frontal current decays with time according to a power law. The deviations of the initial state of the front from the state of geostrophic balance result in the generation of superinertial oscillations of the hydrodynamic fields. 相似文献