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31.
S. C. Tripathy C. B. Dwivedi A. C. Das A. R. Prasanna 《Journal of Astrophysics and Astronomy》1993,14(2):103-114
In this paper, the analytical and numerical results of the stability analysis of the accretion disk at the inner boundary
is presented. Including the effect of finite conductivity in the disk dynamics, a simple calculation considering only the
radial perturbation has been carried out. Within local approximation, it is concluded that the disk is stable to Kelvin-Helmholtz
and resistive electromagnetic modes whereas the magnetosonic mode can destabilise the disk structure. 相似文献
32.
S. C. Tripathy C. B. Dwivedi A. C. Das A. R. Prasanna 《Journal of Astrophysics and Astronomy》1993,14(3-4):167-179
A two-dimensional instability analysis for a magneto-keplerian disk flow around a compact object is presented here. Using
the eigenvalue technique, linearly coupled perturbed equations have been numerically solved within the local approximation.
It is concluded that Kelvin-Helmholtz, magnetosonic (fast and slow) and resistive electromagnetic modes exist. However, only
the magnetosonic mode can destabilise the disk structure. Further, we discuss the properties of different modes as a function
of disk parameters and plot the eigenmode structures for different physical quantities. 相似文献
33.
应用二维磁流体动力学模拟方法数值研究了三层电流片中电阻撕裂模不稳定性的特征及磁场重联过程.结果表明,这是一种复杂的非稳态磁场重联.在初期阶段,三个电流片中分别由撕裂模不稳定性引起磁场重联,形成薄而长的磁岛.随着撕裂模不稳定性的非线性发展,每个磁岛的宽度都逐步增大,以至导致新的磁场重联发生.同时,三个电流片的强度都逐渐减弱,且原中心反向电流区最终消失.部分磁能不断地转化为等离子体的热能和动能,引起等离子体的加热和加速.多层电流片中撕裂模不稳定性引起的自发重联,可能对太阳耀斑、日冕加热、太阳风与磁层耦合等有重要影响. 相似文献
34.
Boris Bardin 《Celestial Mechanics and Dynamical Astronomy》2002,82(2):163-177
We deal with the planar restricted circular problem of three bodies. We study trajectories in a small neighborhood of the Lagrange equilibrium point L
4 when mass ratio is close to Routh's value. In particular, we show that the case of proper degeneracy takes place and for most initial conditions trajectories are conditionally-periodic. We obtain an approximate representation of families of periodic solution emanating from the equilibrium point L
4. We also show that in the case of instability of L
4 the trajectories starting in a vicinity of L
4 remain in a finite domain forever. We give an upper bound of this domain. To carry out our investigation, we analyze the dynamics of a general Hamiltonian system with two degrees of freedom in the case of 1 : 1 resonance in detail.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
35.
Greg Weirs Vikram Dwarkadas Tomek Plewa Chris Tomkins Mark Marr-Lyon 《Astrophysics and Space Science》2005,298(1-2):341-346
As a component of the Flash Center’s validation program, we compare FLASH simulation results with experimental results from
Los Alamos National Laboratory. The flow of interest involves the lateral interaction between a planar M
a
= 1.2 shock wave with a cylinder of gaseous sulfur hexafluoride (SF6) in air, and in particular the development of primary and secondary instabilities after the passage of the shock. While the
overall evolution of the flow is comparable in the simulations and experiments, small-scale features are difficult to match.
We focus on the sensitivity of numerical results to simulation parameters. 相似文献
36.
沿岸流非线性不稳定特征数值研究 总被引:1,自引:0,他引:1
当不稳定剪切波的波幅达到有限幅值之后,需要用非线性不稳定模型来分析沿岸流不稳定运动特征。本文通过建立并验证沿岸流非线性不稳定数学模型,在讨论该模型参数对沿岸流不稳定影响的基础上,率定实验中的模型参数并利用该数学模型模拟了实验中沿岸流不稳定的发展过程及其特征,主要结论有:(1)底摩擦系数越小,侧混系数越小,不稳定发生的时间越早,不稳定的波动幅值越大;(2)沿岸流非线性不稳定演化可能出现的5个阶段(线性阶段、倍周期阶段、大周期阶段、波群阶段以及不规则阶段),实验中出现的沿岸流通常处于线性阶段或非线性倍周期阶段,倍周期阶段的涡旋是由线性阶段的涡旋发生追赶、配对直至合并产生的。涡旋配对以碰撞的形式发生,大部分能量转移至追踪波,然后以较慢的涡旋速度沿岸传播。 相似文献
37.
38.
We have developed an analytical treatment for the wave-induced response of a seabed with inhomogeneous permeability, by employing the boundary layer approximation. By assuming an exponential function for vertically distributed permeability, the inhomogeneous consolidation equation was formulated as Bessel's differential equation. Subsequently, we proposed some representative quantities for examining the effects of inhomogeneity of permeability. The main effects of inhomogeneity are that the boundary layer becomes thinner and the phase delay in the direction of depth becomes larger as the inhomogeneity becomes significant. In addition, it was shown that the boundary layer is properly evaluated by using the averaged permeability. 相似文献
39.
This investigation is an analysis of the influence of landform instability on the distribution of land-use dynamics in a hydrographical basin, located in the Mexican Volcanic Belt mountain range (central Mexico), currently affected by substantial changes in land use and deforestation. A landform map was produced, in addition to seven attribute maps - altimetry, drainage density, slope, relief energy, potential erosion, geology and tectonics - which were considered as factors for determining landform instability through Multi-criteria Evaluation Analysis. Likewise, the direction and rhythm of land-use dynamics were analyzed in four dates - between 1976 and 2000 - and cross tabulations were made between them, in order to analyze the trends and processes of land-use dynamics. Afterwards, the databases obtained were cross tabulated with the landform variables to derive areas, percentages and correlation indices. In the study area, high-instability landforms are associated with most ancient volcanic and sedimentary landforms, where high altitude, drainage density, slope and potential to develop gravitational and fluvial processes are the major factors favouring a land-use pattern, dominated by the conservation of extensive forest land, abandonment of human land use and regeneration of disturbed areas. In contrast, low-instability landforms correspond to alluvial plains and lava hills covered by pyroclasts, where low potential erosion to develop fluvial processes, added to water and soil availability and accessibility, have favoured a land-use pattern dominated by the expansion of agroforestry plantations and human settlements, showing a marked trend towards either intensification or permanence of the current land use and with little abandonment and regeneration. 相似文献
40.
Shi Zhi-dong Li Zhong-yuanUniversity of Science Technology of China Hefei PRC Advanced Centre for Earth Science Astronomy Third World Academy of Science 《紫金山天文台台刊》1996,(2)
Areview about K-H instability related to comet tail is presented.The effect of dust graing on KHI is theoretically analysed and relations of critical shear to excit KHI with the properties of dust grains both for sheared ion flow and for sheared dust flow re put out.Their possible application in comet tail is suggested. 相似文献