Temporal variation of non-ideal plumes with sudden reductions in buoyancy flux
Temporal variation of non-ideal plumes with sudden reductions in buoyancy flux
复制标题
浮力通量突然减少的非理想羽流的时间变化
DOI：
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发表时间：
2008
影响因子：
3.7
通讯作者：
S. Dalziel
中科院分区：
文献类型：
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作者：
M. Scase;Colm‐cille P. Caulfield;S. Dalziel
我们模拟了有限半径和体积通量的孤立源在浮力通量突然下降时的行为，推广了Scase等人提出的先前理论。，第563卷，2006年，第443页)。特别地，我们考虑了一个已建立的羽流的源突然增加的面积，以提供一个更广泛的羽流源的问题。我们的计算预测，虽然我们的模型仍然适用，但羽流永远不会完全挤压成单个上升的热气流。我们报告了大量实验的结果，这些实验提供了一个与理论预测相比较的集合。我们发现，如果源条件被削弱，使众所周知的夹带假设仍然有效，那么所建立的羽流就不会被观察到挤压成单个的热气流。此外，不仅在整体实验中没有观察到掐断现象，而且在任何单个实验中也无法观察到掐断现象。我们同时考虑了羽流剖面的时间演变和被动示踪剂的浓度，并表明我们的模型预测与我们的实验观测结果比较好。
We model the behaviour of isolated sources of finite radius and volume flux which experience a sudden drop in buoyancy flux, generalizing the previous theory presented in Scase et al. (J. Fluid Mech., vol. 563, 2006, p. 443). In particular, we consider the problem of the source of an established plume suddenly increasing in area to provide a much wider plume source. Our calculations predict that, while our model remains applicable, the plume never fully pinches off into individual rising thermals. We report the results of a large number of experiments, which provide an ensemble to compare to theoretical predictions. We find that provided the source conditions are weakened in such a way that the well-known entrainment assumption remains valid, the established plume is not observed to pinch off into individual thermals. Further, not only is pinch-off not observed in the ensemble of experiments, it cannot be observed in any of the individual experiments. We consider both the temporal evolution of the plume profile and a concentration of passive tracer, and show that our model predictions compare well with our experimental observations.