非連續異重流在斜板上的運動

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题名:	非連續異重流在斜板上的運動
其它题名:	Gravity currents from instantaneous sources propagating on sloping boundaries
作者:	陳宥尹;Chen, Yu-Yin
贡献者:	淡江大學水資源及環境工程學系碩士班戴璽恆;Dai, Hsi-Heng
关键词:	異重流;Gravity currents;渠槽實驗;熱體理論;低階模型;斜板;Flume experiment;Thermal theory;Low-dimensional model;Inclined plate
日期:	2012
上传时间:	2013-04-13 12:03:26 (UTC+8)
摘要:	異重流又名為重力流或密度流，是因密度差異所形成的流動現象。流體溫度的變化、溶解或懸浮的物質如鹽及泥沙，皆會造成密度的差異而產生流動現象。近年來，在台灣異重流的研究與水庫的操作和維護緊密相關。夾帶懸浮泥沙的入流進入水庫，即因密度較大而在水庫底部形成異重流往下游方向運移。瞭解異重流在斜坡上的運動特性，可以有效幫助水庫水利排沙的操作。目前，異重流在斜坡上運動的研究可分為連續入流與非連續入流兩類。連續入流的情況下，也可能會形成類似非連續入流所產生的流況。本研究從非連續之異重流在斜坡上運動著手，探討異重流在此情況中之運動特性，於實驗中觀察角度對異重流運移的速度、頭部的空間成長率以及與清水混合、分離的影響，並與目前之理論低階模型做一具體驗證。現階段廣泛使用之非連續異重流在斜坡運動的低階模型是由Beghin, Hopfinger, and Britter (1981 J. Fluid Mech.)所發展的熱體理論(thermal theory)。於本研究發現，隨著角度的增加，異重流頭部長度、高度、最大濃度以及面積的增長率都會隨之增加。 Gravity currents, also known as density currents, are buoyancy-driven flows generated by a density difference. The density difference can be due to a temperature differential, dissolved or suspended materials, e.g. salt and sediments. In recent years, the research in gravity currents has drawn significant attention concerning the operation and sedimentation management of reservoirs in Taiwan. Understanding the characteristics of gravity currents on sloping boundaries can effectively improve the operation and sedimentation removal in reservoirs. At present, the research of gravity currents on sloping boundaries can be divided into two categories based on the inflow condition, i.e. continuous buoyancy inflow and instantaneous (discontinuous) buoyancy release. Even in the continuous inflow case, occasionally the gravity currents generated can be similar to the discontinuous case. Our focus here is on discontinuous gravity currents on sloping boundaries and to study the impact of the slope angle on the characteristics of gravity currents, including the front velocity, the spatial growth rate of the head, entrainment, detrainment, and comparison against the low-dimensional thermal theory. The broadly used thermal theory was developed by Beghin, Hopfinger, and Britter (1981 J. Fluid Mech.). In this study, we found that as the angle increases, the length, height, maximum concentration and area growth rate of head of gravity currents will increase.
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