Continuous convection from an isolated source of heat
Continuous convection from an isolated source of heat
复制标题
来自孤立热源的连续对流
DOI：
10.1002/qj.49708134803
复制
发表时间：
1955
影响因子：
8.9
通讯作者：
F. Ball
中科院分区：
文献类型：
--
作者：
C. Priestley;F. Ball
本文推导了有限范围连续圆形热源上方垂直速度w和温度θ随高度z的变化规律，假定横向分布在源上方不同距离具有相似的形状，并且阻力是w的二次函数。然后，横向分布被认为是高斯的，尽管不是所有的性质都依赖于这个假设。考虑到环境的热分层，得到了完整的解；除非这种分层是中性的，否则垂直热通量随高度恒定的常见假设不再成立。
结果表明，柱的宽度随高度的增加而均匀增加。一般情况下，w在低海拔地区随z增大而减小，但当环境衰减率较大且源区足够广泛时，第二阶段不会发生。在超绝热条件下，第二阶段发生后，第三阶段w又无限制地增加；在亚绝热条件下，在一定的“天花板”高度，w突然减小到零，并推导出一个简单的近似公式。
数值结果说明了这些解决方案在大气污染、防霜和干热问题上的应用。中性条件下的解与雷斯顿的实验室测量结果进行了比较。
Laws are derived for the variation of vertical velocity, w, and temperature, θ, with height, z, above a continuous circular source of heat of finite extent, on the assumptions that the lateral profiles are of similar shape at different distances above the source and that the resistance is a quadratic function of w. The lateral profiles are then taken to be Gaussian, though not all the properties deduced are dependent on this assumption. Complete solutions are obtained allowing for the thermal stratification of the environment; unless this stratification is neutral the common assumption that the vertical heat flux is constant with height is no longer true.
It is shown that the width of the column will increase uniformly with height. In general w increases with z at low elevations and then decreases, but this second stage does not occur when the environmental lapse rate is large and the source area sufficiently extensive. Under superadiabatic conditions the second stage, when it occurs, is followed by a third stage in which w increases again without limit; under subadiabatic conditions w decreases rather abruptly to zero at a certain ‘ceiling’ height, for which a simple approximate formula is derived.
Numerical values illustrate the application of the solutions to problems of atmospheric pollution, frost prevention, and dry thermals. The solution for neutral conditions is compared with Railston's laboratory measurements.