Dynamics of Steady Convections Over Heat and Cool Islands
Dynamics of Steady Convections Over Heat and Cool Islands
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热岛和冷岛稳定对流的动力学
DOI：
10.2151/jmsj1965.53.6_440
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发表时间：
1975
影响因子：
3.1
通讯作者：
R. Kimura
中科院分区：
文献类型：
--
作者：
R. Kimura
本文研究了稳定层状Boussinesq流体中由下边界部分加热或冷却引起的热对流的性质。对于无限小的加热(冷却)，对流运动可以用线性理论来描述。引入适当的标度，结果表明对流主要由一个无量纲参数控制，R=ag*L4/k*，其中*是基本状态下的垂直温度梯度，L是被加热(冷却)区域的半宽，其他符号具有常规意义。对流运动仅限于Stommel和Veronis(1957)提出的“摩擦深度”。对于单板坯对称加热(冷却)，其厚度(温度扰动消失的最低高度)由HT=3.6R-L/6和最大水平速度u*max=0.25，*\Th给出，其中Pr=*/k，Th是被加热(冷却)区域与周围区域之间的温差。上(下)动区的宽度接近于强迫区的水平尺度。通过实验室和数值实验研究了|Th|**L有限幅加热(降温)的对流模式，发现边界层厚度随Th的增加不大。对于加热引起的对流，上升运动区域的宽度随着Th的增加而减小，直到上升运动的大小与水平运动的大小相当。对于冷却引起的对流，下移区域的宽度随着|Th|的增加而增大，但对流型的基本特征与无限小冷却相似。将这些结果与现有的城市热岛效应对流资料进行了比较。
This paper concerns with properties of a thermal convection in a stably stratified Boussinesq fluid caused by partial heating or cooling of the lower boundary. For infinitesimal heating (cooling) the convective motion can be described by a linear theory. Introducing a suitable scaling, it is shown that the convection is controlled mainly by a non-dimensional parameter, R=ag*l4/k* where * is the vertical temperature gradient in the basic state, l is the half-width of the heated (cooled) area and the other symbols have conventional meanings. The convective motion is confined to the "frictional depth" introduced by Stommel and Veronis (1957). For a single slab-symmetric heating (cooling) the thickness (the lowest height at which the temperature perturbation vanishes) is given by hT=3.6 R-l/6 and the maximum horizontal velocity by u*max= 0.25,*\Th\ where Pr= */k and Th is the temperature difference between the heated (cooled) area and the surrounding area. The width of the upward (downward) motion area is close to the horizontal scale of the forcing area. The convection patterns for the finite-amplitude heating (cooling) were investigated by means of laboratory and numerical experiments for |Th|**l. It was observed that increase of the thickness of the boundary layer with Th is small. As for the convection caused by heating, however, the width of the upward motion area decreases with the increase of Th until the magnitude of the upward motion becomes comparable with that of the horizontal motion. As for the convection caused by cooling, the width of the downward motion area increases with |T h|, but the essential features of the convection pattern are similar to those for the infinitesimal cooling. These results are compared with available data of the convection due to the urban heat island effect.