Gravity currents comprise of a wide range of natural phenomena which take place in the atmosphere and the oceans. The mechanics of gravity currents have been thoroughly investigated in the past, but only recently have the compu- tational resources accessible to researchers provided the suitable conditions for examining the details of the fluid dynamics of these phenomena in more complex configurations. The first part of this work entails the prediction of gravity currents which flow through straight channels. This kind of analysis has been extensively investigated in the past, however, differently from the existing research, the effects induced by the impulsive vertical removal of a lock-gate at the interface between the dense and the ambient fluid are examined here for the first time. Despite the fact that numerical studies are often concerned with lock-release density currents, the triggering mechanism which occurs in the early stages of the evolution of the fluid flow has always been neglected. In addition, the interaction between the free surface at the top of the ambient fluid and the density current itself is inspected. The additional physics included in the model leads to greatly improved accuracy of the numerical simulation and provides a very detailed insight into the dynamics associated with the interaction between the density current, the free surface and the moving lock-gate. The second part concerns the modelling of saline gravity currents through three-dimensional submerged channels. In particular, the pattern of 'secondary circulation at the bend apexes of sinuous channels is investigated in order to clarify the contradictory observations which have been highlighted by different workers. The debate as to whether the cross-stream circulation produced by the passage of a gravity current occurs in the same way as in a river (e.g. Imran et al. 2004; Islam & Imran, 2008a) or in a reversed fashion compared to that of a river (e.g. Keevil et al., 2006; Peakall et al., 2007) has been ongoing since 2006. In this thesis an attempt is made to provide an explanation which incorporates and unifies these apparently contradictory results,.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555903 |
| Date | January 2010 |
| Creators | Serchi, Francesco Giorgio |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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