|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。 |
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.