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本文假定上、下平板之间温差随时间按指数规律变化,研究当界于两平板之间流体层的平均温度分布随时间变化时的B(?)nard对流,文中将临界Rayleigh数当作时间的函数,并将其按小参数展开成级数。在时间远离零点时,得到临界Rayleigh数的一个近似到二阶的非常简单的表达式。 相似文献
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层状二维流动的基本方程式 总被引:1,自引:0,他引:1
在很多海洋、大气等二维流动问题中所用的动力学方程往往沿用推广后的河流水力学方程或“纳维-斯托克斯方程”其中把湍流阻力项写成这样的方程式和湍流阻力项用到实际问题上去,无疑是存在着极大的局限性,而将导致矛盾百出。本文则从雷诺方程出发,把所有的物理量沿深度加以平均,求出平均以后的物理量所满足的运动方程,连续方程和扩散方程。 相似文献
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吴烽 《应用数学和力学(英文版)》1987,(10)
The onset of Benard convection. or the critical Rayleigh number in a layer of fluid witha time-dependent mean temperature has been investigated theoretically. The criticalRayleigh number is regarded as a function of time and is expanded in series of a smallparameter. Up to second approximation a simple expression of critical Rayleigh number isobtained for the time region for away from the point of zero. 相似文献
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In many studics on two-dimensional flows in field of atmosphere and ocean theequations which are extension of river-hydraulic equationsor Navier-Stokes equationsare usually used.In these equations stand forturbulent resistance.Obviously use of these equations in practice may lead to contradiction.In this paper the average of Reynolds equations over depth is taken.The motion equations,continuity equation and diffusion equation are obtained for the average physical variables. 相似文献
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