On High-Drag States of Nonlinear Stratified Flow over an Obstacle
On High-Drag States of Nonlinear Stratified Flow over an Obstacle
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障碍物上非线性分层流的高阻力状态
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
R. Pierrehumbert
中科院分区：
文献类型：
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作者：
J. Bacmeister;R. Pierrehumbert
本文对障碍物非线性分层流动中出现的高阻态的性质进行了数值研究。特别是，我们考虑了将阻力增强视为线性共振的理论与试图利用与非线性水力学理论相类比的机制的相对优点。首先，我们研究系统的行为作为施加在环境气流中的零风线高度的函数。高阻力状态的性质与Smith的内部水力分析的预测很好地一致，而不能用线性共振的观点来解释。然而，即使当初始临界能级高度低于最低预测共振高度时，也会出现高阻力状态。在这种情况下，产生上游传播孔，其调整条件以允许高阻力状态。在窄山上的进一步实验表明，非静力效应对最低共振位置的行为没有明显的影响。
Abstract We have carried out a numerical investigation of the nature of high-drag states occurring in nonlinear stratified flow over obstacles. In particular, we consider the relative merits of theories which view the drag enhancement as due to linear resonance vs mechanisms which seek to exploit analogies with nonlinear hydraulic theory. First we examine the behavior of the system as a function of the height of a zero-wind line imposed in the ambient flow. The character of the high-drag states conforms well to the predictions of the internal hydraulic analysis of Smith, and cannot he explained in terms of linear resonance. However, a high-drag state emerges even when the initial critical level height is below the lowest predicted resonant height. In this case an upstream-propagating bore is generated which adjusts conditions so as to allow a high-drag sate. Further experiments with a narrow mountain revealed that nonhydrostatic effects do not appreciably affect the behavior for the lowest resonant positi...