Author(s): Shinjiro Miyawaki
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Keywords: No Keywords
Abstract: This paper discusses results from eddy resolving high resolution numerical simulations of the flow and passive scalar transport (heat transfer) at the confluence of two small streams. At the confluence, the incoming two streams are not parallel, which is typically the case at natural river confluences. The numerical simulation uses Detached Eddy Simulation (DES) to investigate the effects of the large scale coherent structures populating the mixing layer and of the dynamically important streamwise oriented vortices forming at the junction on both sides of the mixing layer on the scalar mixing downstream of the river confluence. The time-averaged distributions of the passive scalar (temperature) are compared with those obtained in a previous field study. Good agreement is observed between the predictions and the measurements. Then, numerical simulations are used to better understand the mechanisms through which the large scale vortex structures and their interactions are driving the scalar transport at the river confluence. The results show that as a result of the two counter rotating streamwise oriented vortices the fluid in the mixing layer is convected away from the mixing layer in the near bed region which explains the temperature profiles in the downstream cross-sections.
Year: 2009