Speed limits on swimming of fishes and cetaceans.

Physical limits on swimming speed of lunate tail propelled aquatic animals are proposed. A hydrodynamic analysis, applying experimental data wherever possible, is used to show that small swimmers (roughly less than a metre long) are limited by the available power, while larger swimmers at a few metres below the water surface are limited by cavitation. Depending on the caudal fin cross-section, 10-15 m s(-1) is shown to be the maximum cavitation-free velocity for all swimmers at a shallow depth.     

水力空化强化臭氧消毒技术的影响因素研究

采用水力空化强化臭氧消毒技术对饮用水进行消毒,考察了臭氧体积流量、多孔板的几何参数及其入口压力、pH值等对消毒效果的影响。试验结果表明：适宜的臭氧体积流量为0．04m^3／h;提高多孔板的入口压力有利于改善消毒效果;在入口压力一定的条件下,多孔板的孔径越小则消毒效果越好,而当总孔周长与总过流面积之比一定时,过流面积比越大则消毒效果越佳;当pH值为4～10时,提高pH值有利于改善灭菌效果;单独水力空化、臭氧氧化以及它们的联合工艺对细菌的杀灭均遵循表观一级动力学模型。     

改进型涡凹气浮工艺浓缩剩余活性污泥试验研究

为了考察改进型涡凹气浮设备MCAF-10浓缩剩余活性污泥的性能,在朝阳洲污水处理厂对MCAF-10浓缩剩余污泥进行了试验研究,结果表明：絮凝剂采用FO4440SH,最佳投加量为1.0 kg/tDS,表面活性剂采用1 227,最佳投加量0.2 kg/tDS,最佳固体负荷和水力负荷分别为270 kgMLSS/m^2.d1、10 m^3/m^2.d,出水SS为100～150 mg/L,与CAF-5浓缩剩余活性污泥时最佳固体负荷和水力负荷分别为230 kgMLSS/m^2.d9、0 m^3/m^2.d,出水SS为200～250 mg/L相比,提高了涡凹气浮污泥浓缩工艺的处理能力,降低了出水SS浓度,MCAF工艺比CAF工艺更适合于剩余活性污泥的浓缩。     

EXPERIMENTAL RESEARCH ON THE SHAPE CHARACTERS OF NATURAL AND VENTILATED SUPERCAVITATION

A series of projectile and water-tunnel experiments were conducted to investigate the shape characters of natural and ventilated supercavitation. It was found that the shape and dimensions of both the natural supercavitation and the ventilated supercavitation are similar through the comparison of them when the cavitation number is small and equal, and the contour of both the natural supercavitation and the ventilated supercavitation can be calculated effectively with the Savchenko formula. The gravity effect can induce the asymmetry of ventilated supercavitation, and the asymmetry is more apparent as the Froude number is smaller. The empirical formula for calculating the axial deformation of ventilated supercavitation was corrected and expanded based on experiment data. The evolution rules of both the natural supercavitation and the ventilated supercavitation were described, and the vortex frequency of natural cavitation was obtained. In addition, the hysteretic aspect was observed between the development and the fall process of ventilated cavitation.     

三门峡大坝双层泄水孔原型噪声观测与底孔改建设计

三门峡大坝泄流排沙孔原为施工导流底孔，其体型不满足黄河高含沙水流的要求，泄水后其斜门槽、工作门槽导轨等部位发生严重破坏。为了查明破坏机理，提出合理的改建措施，于１９８９年对双层泄水孔进行了原型噪声观测。本文介绍了噪声测试水流空化的原理、方法及成果，对照水工模型试验及底孔破坏情况进行了分析，对改建方案进行了论证。此次原型噪声观测为水工建筑物水流空化情况测试和判断提供了新的途径，底孔改建为改善水力条件     

凹曲率完全连续的反弧段体型的研究与应用

泄水建筑物挑流反弧段体型，一般采用斜直线、圆弧、直线相切连接的曲线，因其凹曲主不连续，故溢流时，高速水流发生断续跳动，流态极不稳定，水压分布复杂，加剧空蚀破坏；往往还会缩小挑距，增大起挑流量，影响消能效果，为此，推导的 由直线、过渡曲线、直线的凹曲率完全连续的反弧曲线，解决了传统反弧体型的弊病，并首次在湖南株树桥溢洪道上应用成功，实践证明，此曲线设计理论正确，体型新颖，运行效果好，且施工简便，易于     

凹槽中的旋涡及初生空化数的估算

本文阐述了凹槽中旋涡形成的力学机制；利用文献［1］中的结果建立了凹槽中旋涡的涡量平衡、能量平衡近似关系式；给出了旋涡初生空化数的表达式，它不仅和凹槽的宽深比有关，还和参数K1有关(K1为流道宽和槽深之比)；对不同的深宽比和K1值计算了凹槽中的旋涡参数和初生空化数，把计算的初生空化数和已有的实测凹槽旋涡初生空化数进行了对比，两者的值和变化趋势基本一致。     

墩头超长实用堰泄洪安全分析及模型试验验证——以缅甸DAPEIN(Ⅰ)水电站工程为例

以缅甸DAPEIN(Ⅰ)水电站工程为例,论述了将WES实用堰的闸墩墩头向上游超长延伸之后,对泄洪安全所造成的影响。针对WES实用堰流量系数、堰面动水压力容易受边界因子影响的特点,对设计断面的堰顶布置和墩头形状进行了优化。根据堰面空化数计算公式及水流特性推导出计算的关键部位,对空化数进行计算。采用几何比尺为1∶60的物理模型对溢流堰的泄流能力和堰面动水压力进行了试验测试。试验结果表明:溢流堰的模型试验泄流能力和设计泄流能力非常相近。堰面动水压力除工况2的B4测点出现了-1.2 k Pa的微小负压值外,其余堰面时均压强值均大于0。从而,在泄流能力和堰面动水压力两方面都验证了这种设计方案的合理性。该工程所遇到的结构布置问题在中低溢流坝工程中属常见问题,解决思路可为今后类似工程建设借鉴参考。     

回龙山大坝空蚀破坏问题的试验研究

回龙山大坝挑流鼻坎因体型的原因，导致泄流时产生严重的空蚀破坏。通过模型试验，分析了鼻坎１９９５ 年泄流的水力学条件，进而搞清空蚀破坏的原因。以超空化理论为基点，对鼻坎的体型进行了优化研究。     

Modelling and computation of unsteady turbulent cavitation flows

1. INTRODUCTION Cavitatating flows are important phenomena happened in industry setups and many under-water vehicles. It leads to performance losses and modifications of blade load when happened in machines, especially turbo-machinery. Nevertheless, cavit…