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Seventh International Symposium on Turbulence and Shear Flow Phenomena
July, 28-31, 2011, Ottawa Convention Centre, Ottawa, Canada

DOI: 10.1615/TSFP7

TURBULENT DRAG REDUCTION DUE TO LAMINAR WALL-JET FLOWS, SIMULATING EFFLUX FROM FISH GILLS

pages 1-6
DOI: 10.1615/TSFP7.870
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RESUMO

We have carried out direct numerical simulation for turbulent flow with the injection of laminar wall jets in order to simulate efflux flow from the gills of swimming fish. The bulk-mean velocity of the jet is lower than the maximum velocity of main flow. It is found that a decrease in the turbulence intensity and the negative velocity gradient due to the jet flow lead to a decrease in the Reynolds shear stress, which causes a decrease in the turbulence intensities. A 3.3% reduction of spatiotemporal averaged value of wall shear stress is obtained in the case where the main-flow Reynolds number based on the friction velocity is 150 and the bulk-mean velocity of the jet is five times the friction velocity. This is due to fact that the jet flow weakens the sweep events in a wide region downstream from the place where the jet is located.

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