Standing Alfvén waves with m ≫ 1 in an axisymmetric magnetosphere excited by a stochastic source     

A. S. Leonovich  V. A. Mazur 《Annales Geophysicae》1998,16(8):900-913

In the framework of an axisymmetric magnetospheric model, we have constructed a theory for broad-band standing Alfvén waves with large azimuthal wave number m 1 excited by a stochastic source. External currents in the ionosphere are taken as the oscillation source. The source with statistical properties of –white noise is considered at length. It is shown that such a source drives oscillations which also have the –white noise properties. The spectrum of such oscillations for each harmonic of standing Alfvén waves has two maxima: near the poloidal and toroidal eigenfre-quencies of the magnetic shell of the observation. In the case of a small attenuation in the ionosphere the maximum near the toroidal frequency is dominated, and the oscillations are nearly toroidally polarized. With a large attenuation, a maximum is dominant near the poloidal frequency, and the oscillations are nearly poloidally polarized.  相似文献   

厦门市的震前电磁波观测     

叶清 《福建地震》1998,(3)

本文记述了厦门市地震局几年来开展电磁波观测的情况,以及对各种非震异常信号的识别探索。  相似文献   

波浪在泥床上传播时的波长变化     

王伦明 《热带海洋学报》1991,(3)

本文通过长江口航道淤泥的室内波浪试验研究,认为影响波长变化的主要因素有相对泥床厚度、泥床含沙浓度及相对(传播距离)波长等。在本试验范围内,波浪在泥床上传播时的波长变化一般在±5％以内;但在相对泥床厚度、泥床含沙浓度及相对(传播距离)波长均较大时,波浪被急剧衰减,波长也随之迅速减小。  相似文献   

锦州湾附近水域波浪和海流特征初探   总被引：3，自引：1，他引：3  

刘恒魁 《海洋湖沼通报》1995,(1):1-6

根据戎芦岛海洋站长期波浪观测资料和锦州湾实测海流数据的处理和分析，阐述了研究海区波浪和海流的基本特征及其变化规律。  相似文献   

Wave-power absorption by a periodic linear array of oscillating water columns     

A. F. de O. Falco 《Ocean Engineering》2002,29(10):1163-1186

This paper describes a theoretical analysis of the ocean wave energy absorption by a periodic linear array of oscillating water columns (OWCs) of arbitrary planform. The analysis is based on classical linear water wave theory and uses the expressions for the wave field resulting from time-harmonic pressure distributions on the free surface. The water depth is assumed finite and constant. The cases of oblique and normal incidence are analysed. A linear power take-off mechanism is assumed, but a complex characteristic constant (allowing for phase control) and air compressibility are considered. Special analytical expressions are derived for OWCs of rectangular and circular planforms. Numerical results for circular chambers show that the hydrodynamic interaction can substantially change the maximum energy absorption, depending on array and chamber geometry and on angle of incidence.  相似文献   

Wave-adjusted boundary condition for longshore current in finite-volume circulation models     

Christopher W. Reed  Adele Militello 《Ocean Engineering》2005,32(17-18):2121-2134

Numerical modeling of coastal circulation encompassing the nearshore requires forcing by tide, surface gravity waves, and possibly other factors. In the nearshore, the wave-induced longshore current and setup are dominant hydrodynamic processes, and lateral boundary conditions representing tide and oceanic forcing typically do not include surface-wave contributions. Without proper boundary conditions, significant gradients in current and water level can occur that contaminate the solution in the internal domain. A standard strategy is to place the boundaries far from the site of interest, but this strategy greatly increases computational demands, and it may not be appropriate for long-term simulations. This paper describes a wave-adjusted boundary condition that accounts for wave-induced water level and current acting in combination with tidal forcing. The wave-adjusted boundary condition is demonstrated for an idealized case of a parallel-contour beach and for an engineering application at Ocean City, MD.  相似文献   

Three-dimensional wave patterns in long air cavities on a horizontal plane     

Konstantin I. Matveev   《Ocean Engineering》2007,34(13):1882-1891

Significant drag reduction of large displacement vessels can be achieved by applying multi-wave air cavities arranged on the hull bottom. Waves generated on the air–water interface of air cavities impose requirements on the dimensions of a hull recess that accommodates the air cavity. An approximate model for calculating wave patterns in the critical upstream part of long air cavities in a simplified, horizontal-plane geometry is presented in this paper. The influence of the recess planform boundaries and other factors on the wave patterns is studied parametrically. Some hydrodynamic aspects of multi-wave air cavities are discussed.  相似文献   

Upwelling by a wave pump     

Kern E. Kenyon 《Journal of Oceanography》2007,63(2):327-331

A rigid open-ended pipe is submerged in the ocean below the troughs of the surface waves and held fixed in the vertical position, the lower end being at or below the depth of wave influence. When surface gravity waves propagate past the pipe, water flows up as long as waves are present. The steady upward vertical velocity in the center of the pipe is calculated to be proportional to the square of both the average wave steepness and the pipe’s radius. An application is to bring nutrient rich waters up into the sunlit surface layers of the open oceans.  相似文献   

Assessment of open boundary conditions on the elliptic formulation of the mild-slope equation     

Filipa Simes Brito Ferreira Oliveira 《Ocean Engineering》2004,31(11-12):1567-1576

The performance of open boundaries in a finite differences scheme of the elliptic mild-slope equation is assessed. The wave propagation results show that lowest order parabolic radiation boundary conditions, unlike sponge layers combined with first order radiation boundary conditions, are an efficient alternative to first order radiation boundary conditions in order to improve the accuracy of the numerical solution of the problem.  相似文献   

Latching control of deep water wave energy devices using an active reference     

Umesh A. Korde   《Ocean Engineering》2002,29(11):1343-1355

This paper investigates latching type control on a floating wave energy converter in deep water. An on-board, actively controlled motion-compensated platform is used as a reference (‘active reference’) for power absorption and latching. A variational formulation is used to evaluate an optimal control sequence in the time domain. Time domain simulation results are presented for a heaving buoy in small-amplitude waves. Results are compared with an equivalent system where latching and power absorption are from a sea-bottom-fixed reference.  相似文献