Natural ventilation of an enclosure containing two buoyancy sources
Natural ventilation of an enclosure containing two buoyancy sources
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DOI：
10.1017/s0022112096002546
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发表时间：
1996-03-25
影响因子：
3.7
通讯作者：
Linden, PF
中科院分区：
文献类型：
--
作者：
Cooper, P;Linden, PF
本文描述了包含两个浮力点源的自然通风外壳的实验和理论模型。先前关于由于存在单一浮力源而在空间中发展的流动和分层的工作已扩展到涵盖正浮力或负浮力的两个来源，以试图产生更现实的实际问题模型。例子包括自然通风的建筑物，以及涉及通过气流扩散污染物的工业或医疗过程。实验技术涉及使用充满水的外壳，并在两个点注入盐溶液。这些负浮力源在外壳内形成湍流羽流。发现两个不同强度的来源产生由三个不同的、完全混合的层组成的垂直密度分布。该论文描述了一个成功预测这些层的深度和密度的理论模型。发现三层之间的界面位置仅是外壳开口的有效面积A*、外壳的高度H以及两个浮力源B-1/B-2的强度比的函数。还检查了在外壳的下边界处具有一个正浮力源并且在外壳的上边界处具有一个负浮力源的系统的行为。该案例与同时存在冷表面和暖表面的房间中的热分层预测特别相关。同样，界面的高度仅取决于外壳的几何形状和源强度比。预测并观察到三种不同类型的流动模式。
This paper describes experiments and theoretical modelling of a naturally ventilated enclosure containing two point sources of buoyancy. Previous work on the flow and stratification that develop in a space owing to the presence of a single source of buoyancy has been extended to cover two sources of positive or negative buoyancy in an attempt to produce more realistic models of practical problems. Examples include naturally ventilated buildings, and industrial or medical processes involving dispersal of contaminants by air currents. The experimental technique involves the use of a water-filled enclosure with salt solution injected at two points. These sources of negative buoyancy form turbulent plumes within the enclosure. Two sources of unequal strength are found to produce a vertical density profile consisting of three distinct, fully mixed layers. The paper describes a theoretical model that successfully predicts the depths and densities of these layers. The positions of the interfaces between the three layers were found to be a function only of the effective area A* of the enclosure openings, the height of the enclosure H and the ratio of the strengths of the two sources of buoyancy B-1/B-2. The behaviour of a system with one source of positive buoyancy at the lower boundary and one of negative buoyancy at the upper boundary of the enclosure is also examined. This case has particular relevance to the prediction of thermal stratification in rooms with both cold and warm surfaces present. Again the height of the interfaces is dependent only on the geometry of the enclosure and the source strength ratio. Three distinct types of flow pattern are predicted and observed.