Dissipative heating in convective flows
Dissipative heating in convective flows
复制标题
对流中的耗散加热
DOI：
10.1017/s002211207500119x
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发表时间：
1975
影响因子：
3.7
通讯作者：
N. Weiss
中科院分区：
文献类型：
--
作者：
J. Hewitt;D. McKenzie;N. Weiss
耗散加热是由对流流体中的不可逆过程产生的，例如粘性加热或欧姆加热;其重要性取决于对流区域的深度与温标高度的比值d/HT。对定常流的熵方程进行积分，得到对流层中耗散加热总速率的上限。对于液体，存在耗散加热与对流热通量的比率约等于c（d/HT）的状态，其中常数c与瑞利数无关。这一结果证实了使用Boussinesq近似，这是有效的，只有当d/HT是小的数值实验。对于深层，耗散加热率可能远大于对流热通量。如果地球的磁场是由一个对流驱动的发电机维持的，那么欧姆损耗被限制在从核心出现的对流通量的5%。在地幔中，在洋脊下面和岛弧后面的局部地区，粘性加热可能是重要的。
Dissipative heating is produced by irreversible processes, such as viscous or ohmic heating, in a convecting fluid; its importance depends on the ratio d/HT of the depth of the convecting region to the temperature scale height. Integrating the entropy equation for steady flow yields an upper bound to the total rate of dissipative heating in a convecting layer. For liquids there is a regime in which the ratio of dissipative heating to the convected heat flux is approximately equal to c(d/HT), where the constant c is independent of the Rayleigh number. This result is confirmed by numerical experiments using the Boussinesq approximation, which is valid only if d/HT is small. For deep layers the dissipative heating rate may be much greater than the convected heat flux. If the earth's magnetic field is maintained by a convectively driven dynamo, ohmic losses are limited to 5% of the convected flux emerging from the core. In the earth's mantle viscous heating may be important locally beneath ridges and behind island arcs.