Condensation of water vapour carried by buoyant atmospheric plumes is responsible for cloud formation and leads to a release of latent heat. This release provides a secondary source of buoyancy away from the origin of the plume, and field observations suggest that the laterally entraining plume model does not capture the resulting behaviour correctly. To investigate this problem in the laboratory Bhat and Narasimha (1996) reproduced analogous off-source heating by using electrodes to heat an acidic jet in a deionised ambient. It was observed that the heating significantly disrupted the eddy structure of the jet and the mass flux was drastically reduced. This dissertation describes a numerical investigation of volumetrically heated jets. The numerical approach taken employs a method known as Monotone Integrated Large Eddy Simulation (MILES). It is a natural form of large eddy simulation that can capture inherently the correct flow of energy through the inertial range, and provides physical decay at the grid-scale cut-off. The method does not use an explicit turbulence model and hence makes no assumptions about the structure of the flow. The extent to which turbulent statistics can be recovered with such an approach is first explored, in the context of homogeneous turbulence. Open shear flows are then considered, first in a temporally evolving circular shear layer. Finally, spatially evolving jets with and without off-source heating are investigated. The results confirm observations made in experimental and numerical studies, but also provide further insight. Measurements, particularly of second-order correlations, help to clarify the understanding of this flow, and identify further requirements necessary for an analytic model to capture fully the phenomena observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596195 |
| Date | January 2006 |
| Creators | Aspden, A. J. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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