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INVESTIGATION ON 3-D STRUCTURE IN SIDE-CAVITY OPEN-CHANNEL FLOW BY LES

Kouki Onitsuka
Department of Civil and Global Environment Engineering, Kyoto University; Department of Civil Engineering, Kyushu Institute of Technology Kita-Kyushu, 804-8550, Japan

Masaru Ura
Hinosato 9-5-5, Munakata, Fukuoka 811-3425, Japan

Juichiro Akiyama
Department of Civil Engineering, Kyushu Institute of Technology Kita-Kyushu, 804-8550, Japan

Iehisa Nezu
Dept. of Global Environment Engineering, Kyoto University Kyoto, 606-8501, Japan

Аннотация

A numerical simulation of an open-channel flow with a side cavity has been carried out by making use of an LES (large eddy simulation). In this study, the Froude number was set to 0.1, based on the study by Kimura et al.( 1997), that the fluctuations of free surface are negligibly small in such a low Froude number flow. The time-averaged velocity vector, distributions of the Reynolds stress and kinetic turbulent energy are similar to those of experimental data which were obtained by Nezu & Onitsuka(2001) with an LDA (laser Doppler anemometer). It was found that the instantaneous velocity vector is quite different from the time-averaged one. The calculated flow field is almost 2-dimensional in the vertical direction except for very near the bed. This result corresponds to the experimental data which was shown by Nezu et al.(2000) with a PIV (particle image velocimetry) It was found that the weak up-flow was generated at the central pivot of the time-averaged horizontal vortex and that the shape and the strength of the instantaneous horizontal vortex in the same time change in the vertical direction.