The transition of a line plume to round plume
The transition of a line plume to round plume
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DOI：
10.1007/s10652-022-09852-7
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发表时间：
2022-03
影响因子：
2.2
通讯作者：
N. Kaye;Dylan M. Robinson;R. Akhter;Md Safwan Ahsanullah;Ta’Jon A. Jordan;Oscar E. Martinez
中科院分区：
文献类型：
--
作者：
N. Kaye;Dylan M. Robinson;R. Akhter;Md Safwan Ahsanullah;Ta’Jon A. Jordan;Oscar E. Martinez
浮力湍流羽流通常按其几何形状分类，并被描述为从点源发出的圆形羽流或从细长源发出的线/平面羽流。当线状羽状物上升到它们的源上方时，它们变得更厚（垂直于源轴），并且远离源，它们将不再是平面的，而是更像一个圆形羽状物。然而，绝大多数线羽流的实验测量集中在近源区，在那里它们仍然是平面的，流动是二维的。此外，这些实验用障碍物约束羽流的端部，以防止通过羽流的端部的夹带并保持二维流动。在这里，结果是从一系列的实验，进行测量的过渡到一个圆形的羽流不受约束的线羽。提出了一种模型，该模型允许计算的夹带到羽流的任意横截面形状的水力半径的羽流定义为横截面积除以周长夹带发生。这个配方，沿着与一个平滑的过渡函数，改变的几何形状和夹带系数，是用来预测的前位置随着时间的推移，为线羽流在填充盒。该模型针对不同的喷嘴宽度与盒高度比的值运行。该模型的结果进行了比较，实验前的位置测量和显示，一个不受约束的线羽流将过渡到一个圆形羽流的高度等于约三倍的源宽度。这与当线羽流的厚度与其喷嘴宽度的大小相似时，线羽流将转变的想法一致。
Buoyant turbulent plumes are often categorized by their geometry and described as either round plumes, issuing from a point source, or line/planar plumes, issuing from an elongated source. As line plumes rise above their source they get thicker (normal to the source axis) and, far from the source, they will no longer be planar but more resemble a round plume. However, the vast majority of experimental measurements of line plumes focus on the near source region, where they are still planar and the flow is two-dimensional. Further, these experiments constrain the ends of the plume with barriers to prevent entrainment through the ends of the plume and maintain a two-dimensional flow. Herein, results are presented from a series of experiments that were conducted to measure the transition of an unconstrained line plume into a round plume. A model is presented that allows the calculation of the entrainment into a plume of arbitrary cross sectional shape in terms of the hydraulic radius of the plume defined as the cross-sectional area divided by the perimeter over which entrainment is occurring. This formulation, along with a smooth transition function that changes both the geometry and entrainment coefficient, is used to make predictions of the front position over time for a line plume in a filling box. The model was run for different values of the nozzle width to box height ratio. Results of the model were compared to the experimental front position measurements and show that an unconstrained line plume will transition to a round plume at a height equal to approximately three times the source width. This is consistent with the idea that the line plume will transition when its thickness is similar in magnitude to its nozzle width.