The importance of model plane location and movement in dense discharge assessment

Mead, C.T. and Bourban, S. and Cawthorn, C.J. and Turnbull, M. (2011) The importance of model plane location and movement in dense discharge assessment. In: International Symposium on Outfall Systems, 15-18 May 2011, Mar del Plata, Argentina.

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Abstract

As dense plumes in the sea tend to form relatively thin layers at the seabed, flexible model vertical structure is needed to provide optimal resolution of plumes without requiring excessive computational resources. An Automatic Mesh Redistribution (AMR) method, based on a generalisation of the traditional sigma mesh, is presented, and demonstrated in application to the simulation of dense plume dispersion in the sea. The results of preliminary simulations for schematic and more realistic test cases are encouraging. It is demonstrated that the AMR method can adapt to relatively thin dense plumes, without the iterative refinement of plane locations that would be required to achieve similar results with some form of sigma mesh. The main details of plumes simulated with the AMR method are shown to be very similar to those obtained with a traditional sigma mesh after such a refinement process. The preliminary results presented here are to be investigated further, and will form the basis of an enhanced set of test cases. To date, only the clustering of model planes around steep vertical gradients in the concentration of a single tracer has been considered. However, the technique can be extended to multiple tracers, velocity shear, and/or other physical or derived quantities. Comprehensive data sets defining dense plume thicknesses in the field have not been available until relatively recently. It is planned to further test the AMR method in the light of a new data set in the near future.

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