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Numerical Studies on the Dynamic Coupling of a Near Field and a FAR Field Model

Author(s): C. O. Horita; T. Bleninger; J. L. B. De Carvalho; R. Morelissen; T. Van Der Kaaij

Linked Author(s): Tobias Bleninger, Robin Morelissen

Keywords: Dynamic model coupling; Near field model; FAR field model; Wastewater discharges; Thermal discharges

Abstract: Models have been used to predict impacts from outfall discharges, and as the near and the far field processes occur in very different spatial and temporal scales, the existing models are not capable of simulating the entire discharge in a feasible way. So different numerical models are used for the near and the far field. In order to account the effects of the far field in the near field, the offline coupling method (non-dynamic and one way) has been applied. More recently a dynamic and online coupling had been proposed to also account the effects of the near field in the far field, using the DESA (Distributed Entrainment Sink Approach) methodology with the model CORMIX for the near field and Delft3DFLOW for the far field. To analyse in which cases this dynamic coupling should be applied and in which cases it makes no difference in the results, four tests have been performed. These tests have been made in a straight channel with a steady state flow and with a submerged discharge, varying the discharge flow and the ambient velocity. An application of the near field stability criteria proposed by Bleninger (2006) and also the ambient Froude number calculation were accomplished to the tests. The obtained results were: offline and dynamic coupling induced velocities, the areas occupied by these velocities and the percentage difference of these areas. These results showed that different coupling methods had led to distinct results for all tests, especially in the near field region. The result analysis of the stability criteria demonstrated that the Tests #2 and #4 are unstable and thus should use the dynamic coupling, but the induced velocity areas and ambient Froude number analysis indicated a different result where the Tests #2 and #3 led to a similar behaviour with each other. As the results do not lead to a unique conclusion, the stability criteria should be modified and this will be analysed in the next steps of this research.


Year: 2016

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