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881.
A study of SAR remote sensing of internal solitary waves in the north of the South China Sea:I.Simulation of internal tide transformation 总被引:2,自引:1,他引:1
For settlement of the well-known problem of contemporary radar imaging models,i.e.,the pmblem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal watels at at high radar frequency bands(X-band and C-band),the impact of the ocean surface mixed layer turbulence and the significance of strat-ified oceanic model on SAR remote sensing of internal solitary waves are proposed.In the north of the South China Sea by utilizing seme observed data of background field the nonlinearity coefficient,the dispersion coefficient,the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately.Through simulations of internal tide transfor-mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of intereal wave field are obtained.The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m,but the maximum current speeds take place at depth 20 m in this area of the sea(about 20°30'N,114°E)in August.It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation.The obtained results provide the possibility for the simulation of SAR signatures of inter-nal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper. 相似文献
882.
无限水深聚焦波完全非线性数值模拟 总被引:1,自引:1,他引:0
基于势流理论提出一种新的高阶边界元方法对无限水深的聚焦波浪进行完全非线性数值模拟.自由水面满足完全非线性边界条件,模拟波浪的非线性效果可以达到更高阶.利用镜像原理,建立一种全新的格林函数应用到无限水深的数值波浪水槽中,以致于两无限深水槽侧壁的积分可以被排除.为了产生相应的入射波和吸收出流波浪,一个由点源组成的造波装置被布置于计算域内,同时人工阻尼层被用来吸引出流波浪,由波浪聚焦的方法得到极限波浪.通过开展线性和完全非线性聚焦波浪的数值实验及与理论解对比,验证本数值模型可以用来模拟无限深水域的极限波浪,且在出流边界没有反射. 相似文献
883.
884.
Quan-Ming Lu Shui Wang School of Earth Space Sciences University of Science Technology of China Hefei 《中国天文和天体物理学报》2005,5(2):184-192
We carried out one-dimensional hybrid simulations of resonant scattering of protons and He^2 ions by ion cyclotron waves in an initially homogeneous, collisionless and magnetized plasma. The initial ion cyclotron waves have a power spectrum and propagate both outward and inward. Due to the resonant interaction with the protons and He^2 ions, the wave power will be depleted in the resonance region. Both the protons and He^2 ions can be resonantly heated in the direction perpendicular to the ambient magnetic field and leading to anisotropic velocity distributions, with the anisotropy higher for the He^2 ions than for the protons. At the same time, the anisotropies of the protons and He^2 ions are inversely correlated with the plasma β‖p=8πnpkBT‖p/B0^2, consistent with the prediction of the quasilinear theory (QLT). 相似文献
885.
886.
In an attempt to identify the molecular shocks associated with the entrainment of ambient gas by collimated stellar winds from young stars, we have imaged a number of known molecular outflows in H2 v=1-0 S(1) and wide-band K. In each flow, the observed H2 features are closely associated with peaks in the CO outflow maps. We therefore suggest that the H2 results from shocks associated with the acceleration or entrainment of ambient, molecular gas. This molecular material may be accelerated either in a bow shock at the head of the flow, or along the length of the flow through a turbulent mixing layer. 相似文献
887.
We investigate the recent proposal made by Rees and Mészáros (1994) that GRBs result from internal shocks in the relativistic wind emerging from two coalesced neutron stars. Using a simple model of that wind, where a large number of layers with different Lorentz factors interact through a series of mildly relativistic shocks we compute the efficiency of the process and the time profile of the resulting burst. We show that a great variety of profiles can be obtained using plausible initial distributions of Lorentz factors in the wind. However, the rather low overall efficiency (< 10%) of the process and limits imposed on the burst duration can be used to put severe constraints on the nature of the energy source. 相似文献
888.
Walter Dehnen 《Monthly notices of the Royal Astronomical Society》2005,360(3):892-900
Collisionless stellar systems are driven towards equilibrium by mixing of phase-space elements. I show that the excess-mass function [where is the coarse-grained distribution function] always decreases on mixing . D ( f ) gives the excess mass from values of . This novel form of the mixing theorem extends the maximum phase-space density argument to all values of f . The excess-mass function can be computed from N -body simulations and is additive: the excess mass of a combination of non-overlapping systems is the sum of their individual D ( f ). I propose a novel interpretation for the coarse-grained distribution function, which avoids conceptual problems with the mixing theorem.
As an example application, I show that for self-gravitating cusps ( ρ∝ r−γ as r → 0 ) the excess mass D ∝ f −2(3−γ)/(6−γ) as f →∞ , i.e. steeper cusps are less mixed than shallower ones, independent of the shape of surfaces of constant density or details of the distribution function (e.g. anisotropy). This property, together with the additivity of D ( f ) and the mixing theorem, implies that a merger remnant cannot have a cusp steeper than the steepest of its progenitors. Furthermore, I argue that the cusp of the remnant should not be shallower either, implying that the steepest cusp always survives. 相似文献
As an example application, I show that for self-gravitating cusps ( ρ∝ r
889.
RayQ.Lin WillPerrie 《中国海洋湖沼学报》2005,23(2):129-143
A tetrad mechanism for exciting long waves, for example edge waves, is described based on nonlinear resonant wave-wave interactions. In this mechanism, resonant interactions pass energy to an edge wave,from the three participating gravity waves. The estimated action flux into the edge wave can be orders of magnitude greater than the transfer fluxes derived from other competing mechanisms, such as triad interactions. Moreover, the numerical results show that the actual transfer rates into the edge wave from the three participating gravity waves are two- to three- orders of magnitude greater than bottom friction. 相似文献
890.
结合气象观测和大气边界层探测资料,分析了1990年1月2日重庆雾的声雷达回波特征,并与1989年12月30日雾的回波作了比较。结果表明,雾顶回波高度与逆温和相对湿度的转折高度一致;雾顶回波在雾的成熟期呈现波动,在消散期有一下降过程。上午大气污染物地面浓度的变化与逆温混合层状况有密切关系,混合层较薄且持续时间较长时,地面浓度较大 相似文献