Physical modelling and scale effects of air-water flows on stepped spillways

查看全文 作　　者：CHANSON [1]Hubert;GONZALEZ Carlos [1]A. 机构地区：[1]Department of Civil Engineering, The University of Queensland, Brisbane 4072, Australia,Department of Civil Engineering, The University of Queensland, Brisbane 4072, Australia 出　　处：《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》索引2005年第6卷第3期,共8页 基　　金：Project supported by the National Council for Science and Tech-nology of Mexico (CONACYT) 摘　　要：During the last three decades, the introduction of new construction materials (e.g. RCC (Roller Compacted Concrete), strengthened gabions) has increased the interest for stepped channels and spillways. However stepped chute hydraulics is not simple, because of different flow regimes and importantly because of very-strong interactions between entrained air and turbu- lence. In this study, new air-water flow measurements were conducted in two large-size stepped chute facilities with two step heights in each facility to study experimental distortion caused by scale effects and the soundness of result extrapolation to pro- totypes. Experimental data included distributions of air concentration, air-water flow velocity, bubble frequency, bubble chord length and air-water flow turbulence intensity. For a Froude similitude, the results implied that scale effects were observed in both facilities, although the geometric scaling ratio was only Lr=2 in each case. The selection of the criterion for scale effects is a critical issue. For example, major differences (i.e. scale effects) were observed in terms of bubble chord sizes and turbulence levels al- though little scale effects were seen in terms of void fraction and velocity distributions. Overall the findings emphasize that physical modelling of stepped chutes based upon a Froude similitude is more sensitive to scale effects than classical smooth-invert chute studies, and this is consistent with basic dimensional analysis developed herein. 关 键 词：泄洪道 物理模型 刻度 空气-水流体 设计方案 水下隧道