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LARGE-EDDY SIMULATION OF STRAIGHT COMPOUND OPEN-CHANNEL FLOWS

Satoshi Yokojima
Department of Social and Environmental Engineering, Graduate School of Engineering, Hiroshima University 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-852; Department of Systems Engineering, Shizuoka University Hamamatsu 432-8561, Japan

Yoshihisa Kawahara
Department of Social and Environmental Engineering, Graduate School of Engineering, Hiroshima University 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan

Abstrakt

We perform large-eddy simulations of incompressible fully developed turbulent flow in a straight open channel with one flood plain using a dynamic two-parameter model, for depth ratios Dr (≡ h/H) equal to 1/2 and 1/4. The Reynolds numbers based on the hydraulic radius and bulk mean velocity, Rem, are 5470 (for Dr = 1/2) and 4670 (for Dr = 1/4). Particular emphasis is placed on a case of low depth ratio; Dr = 1/4, where interaction between the main channel and the flood plain is significant and is therefore of practical interest. Overall, the computational results agree quite well with laboratory measurements by Tominaga and Nezu [J. Hydr. Engrg. ASCE 117(1991) 21] in spite of difference in their Reynolds numbers and show that the LES code using a sophisticated SGS model is a promising tool for natural river predictions.