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Numerical Study on Mixing Process of Density Current in a Brackish Lake Enhanced by Bed Mounted Obstacles

Author(s): T. Kudo; I. Kimura; Y. Shimizu; H. Yasuda

Linked Author(s): Yasuyuki Shimizu, Ichiro Kimura

Keywords: Salinity intrusion; 3D turbulence flow; Flow control block

Abstract: This paper presents a numerical study on a new simple method to enhance the mixing of salt water and pure water in salt wedge advancing into a brackish lake. In recent years, the environment of brackish lakes is being changed by decreasing of river flow rate and rising of sea level because of global warming. For example, in the Lake Abashiri in Hokkaido, Japan, the inflow of saline water from the Sea of Okfotsk through the Abashiri River sometimes causes blue tides, which seriously damage aquatic lives. In order to mix the dense saline water with pure water, we tried to introduce multiple flow control blocks, which form impinging-shear-layer instability and may enhance the mixing effectively. We used three dimensional numerical turbulence model in a density current to clarify the phenomena. First, we applied the numerical models to the flow with a permeable block and turbulence model was tuned through the comparison with the experiment. We considered 0-equation model and2-equation models. Then the models were applied to the flow with impermeable blocks. We consider numerically the effect of distance and number of blocks on feedback effects of impinging shear layers.


Year: 2010

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