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3rd Thermal and Fluids Engineering Conference (TFEC)

ISSN: 2379-1748

DIRECT NUMERICAL SIMULATION ON TURBULENT FLOW OVER TRUNCATED PYRAMID IN AN OPEN CHANNEL

Mitsuhiro Shintani
Yamamoto Kogaku Co., LTD., Higashi-Osaka City, Osaka 577-0056, Japan

K. Nakatsuji
Graduate School of Science and Technology, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan

M. Matsumoto
Graduate School of Science and Technology, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan

Yoshimichi Hagiwara
Department of Mechanical and System Engineering, Graduate School of Science and Technology, Kyoto Institute of Technology Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan

DOI: 10.1615/TFEC2018.tfl.022349
pages 1849-1858


KEY WORDS: drag reduction, wavy surface, truncated pyramid, measurements

Abstract

We had previously measured the total drag of truncated pyramids whose surfaces had been shaped in wavy forms. The results had shown a reduction of total drag when compared with that in the case of a truncated pyramid with smooth surfaces, although all the truncated pyramids had had the same projected area to the main flow direction. We carried out direct numerical simulation for turbulent flow around a truncated pyramid to elucidate the mechanism of the total drag reduction. We used an immersed boundary method to express the two-dimensional truncated pyramid. The height of the truncated pyramid was 45.9 wall units, while the flow depth was 360 wall units. In the case of the truncated pyramid with smooth surfaces, it was found from the computational results that the mean velocity increased in the range near the uphill face of the truncated pyramid. The values of turbulence intensities and Reynolds shear stress were high in this region. The mean velocity decreased in the range near the downhill face of the truncated pyramid. These regions were consistent with the regions where vortices had appeared intermittently in the previous experiments.

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