An analytical and experimental study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. The theoretical discussion considers slumping, supercritical gravity currents, i.e. those that generate an interfacial disturbance whose speed of propagation matches the front speed, U and follows from the classical analysis of Benjamin [J. Fluid Mech. 31, pp. 209-248, 1968]. In contrast to previous investigations, the amplitude of the interfacial disturbance is parameterized so that it can be determined straightforwardly from ambient layer depths. The theoretical model, which is applicable to the special case where the depth, D, of the gravity current fluid at the initial instant spans the channel depth, H, shows good agreement with experimental measurements and also analogue numerical simulations performed in conjunction with the present investigation. Unfortunately, it is difficult to extend our theoretical results to the more general case where D < H. Reasons for this difficulty will be discussed.
From experimental and numerical observations, the interface thickness is observed to negligibly affect the speed of supercritical gravity currents even in the limit where the interface spans the channel depth so that the ambient fluid is linearly stratified over the whole of its depth. Conversely, subcritical gravity currents show a mild upward trend of U on the interface thickness. Finally, the effects of densities, ambient depths, interface thickness and D on the horizontal position, X where deceleration first begins are considered. In contrast to the uniform ambient configuration, the gravity current can propagate without decelerating beyond 12 lock lengths and decelerate as early as 1 lock length. / Thermo Fluids
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:AEU.10048/1687 |
| Date | 06 1900 |
| Creators | Tan, Alan |
| Contributors | Flynn, Morris (Mechanical Engineering), Fleck, Brian (Mechanical Engineering), Nobes, David (Mechanical Engineering), Sutherland, Bruce (Department of Mathematical and Statistical Sciences) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 8608851 bytes, application/pdf |
| Relation | Tan, A., D. Nobes, B. Fleck, M. Flynn (2010a). Gravity currents in two-layer stratified media. Journal of Environmental Fluid Mechanics, 1-21. 10.1007/s10652-010-9174-z, Tan, A., D. Nobes, B. Fleck, M. Flynn (2010b). Partial depth gravity currents in two-layer stratified media. Part 1: A study of the wave amplitude. In International Conference of Environmental Science and Engineering. World Academy of Science and Engineering. |
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