Fin performance of 3-D aerator devices with backward lateral deflectors

In the present work,a 3-D aerator device with backward lateral deflectors,called BLD-3-D aerator device,is developed,and the lateral cavity and fin performance of the BLD-3-D aerator device are experimentally investigated.The findings show that,the relative lateral cavity length with backward lateral deflectors is shorter than that with current lateral deflectors under the same approach flow conditions,and on the basis of the results of the relative cavity length ratio between the lateral and bottom aerators the BLD-3-D aerator device is of remarkable performance for the water fin control thanks to the decrease of the relative lateral cavity length.

Fin characteristics of aerator devices with lateral deflectors

The fins will be formed if the lateral deflectors in the side-walls with a bottom aerator device are improperly designed, and the flow regime downstream of the aerator device will be worsened. In this paper, the height and the length of the fins induced by the lateral deflectors are theoretically analyzed along with their influencing factors, and the fin characteristics are experimentally investigated on the basis of the theoretical analysis. It is shown that the intensities of the fins are strongly dependent on the ratio of the lateral cavity length to the bottom cavity length, and other factors, like the working head, the height and the angle of the lateral deflector, the flow Froude number around the aerator device, affect the fins indirectly through the changes of the lateral cavity length. When an aerator device with lateral deflectors is designed, it is crucial to match the above mentioned ratio, and to make the ratio of the two cavity lengths less than 1.0 in order to avoid the generation of the fins.

侧墙掺气坎空腔长度初探

侧空腔长度是侧墙掺气坎设计时考虑的重点内容。采用模型试验和三维数值模拟,对侧墙掺气坎空腔长度的影响因素进行了探讨。结果表明,用紊流数学模型来模拟泄水道反弧末端侧墙掺气坎的空腔长度是可行的;侧墙掺气坎空腔长度不仅与侧墙掺气坎的体型尺寸有关,还与底部掺气坎的体型尺寸有很大关系。在设计侧墙掺气坎时,需同时考虑底部掺气坎的尺寸。

突扩突跌掺气坎底空腔长度计算

突扩突跌掺气坎的底空腔长度既与水力条件和底部掺气坎结构参数有关,也与侧墙掺气坎结构参数有关。以往的底空腔长度计算方法,均针对仅采用底部掺气坎,未设置侧墙掺气坎这类掺气设施,不能反映出侧墙掺气坎结构参数对底空腔长度的影响。基于射流微元体受力平衡法,提出了一种求解明流泄水道突扩突跌掺气坎底空腔长度的计算方法,该方法能够全面反映突扩突跌掺气坎底空腔长度受底部掺气坎、侧墙掺气坎结构参数和水力学参数的影响。通过与30组试验资料和已有研究成果的对比,表明所提出的计算方法具有较高的精度。

侧掺气空腔长度计算

对泄水建筑物过流面进行掺气是一种有效的减蚀措施。采用常规的底部掺气设施后,泄水建筑物下游侧墙仍易发生空蚀破坏,其主要原因是边墙存在掺气盲区。在底掺气的基础上设置侧掺气坎,形成较小的侧空腔能明显提高下游近壁掺气浓度,有效消除原掺气盲区。影响掺气设施掺气效率的一个重要设计参数就是空腔长度,对侧空腔长度尚缺乏计算方法,它的形成机理与底空腔不同。本文笔者通过考虑影响侧空腔长度的结构参数和水力学参数,导出了一种近似计算侧空腔长度的计算方法。

明流泄水道突扩突跌掺气设施空腔长度研究

为了查明短有压进口泄洪洞下游明流泄水道上突扩突跌掺气设施底、侧空腔长度随掺气坎尺寸和水流弗劳德数的变化规律,采用模型试验,测试了不同掺气坎尺寸在不同水流条件下的底、侧空腔长度,分析了无量纲底、侧空腔长度与掺气坎尺寸和水流弗劳德数的相互关系。结果表明:底空腔长度随着挑坎高度的增加、挑坎坡度的增大、侧扩宽度的增加和水流弗劳德数的增大而增大;侧空腔长度与挑坎高度、挑坎坡度关系不大,随着侧扩宽度的增加而增大,随水流弗劳德数的变化规律为:当侧扩宽度较大时,侧空腔长度随水流弗劳德数的增大而线性增大;当侧扩宽度较小时,侧空腔长度随水流弗劳德数的增大而略微减小。

侧掺气空腔长度计算方法研究

掺气空腔长度是衡量掺气减蚀效果的核心水力指标。针对关于侧掺气空腔长度计算方法的研究成果偏少的现状,通过模型试验和量纲分析,对陡槽上不同坎高和坡度侧掺气坎的空腔特性和射流扩散特性开展了研究,分析侧掺气坎体型参数及来流水力学参数对侧空腔长度的影响,推导出侧空腔长度计算公式,并采用多组实验数据进行了验证。结果表明该公式能较准确地估算侧掺气空腔长度。

Hydraulics of a multiple slit-type energy dissipater

With the constructions of high dam projects in China, the energy dissipation downstream of a dam becomes a serious concern. In this study, a multiple slit-type energy dissipater, with different reduction size slits in the outlet, is developed on the basis of conventional slit-type energy dissipaters, aiming to enhance the energy dissipation through the turbulence and the friction between the different layers of the jet flow and the air entrainment due to the increased surface of the flow to the air. The hydraulic characteristics of the energy dissipater are experimentally investigated by means of three sets of physical models in nine cases, to characterize the geometric parameters with suitable performance. The main concerns are the flow regime, the jet flow trajectory, the energy dissipation, the cavitation characteristics, and the flow choking. The results indicate that the dissipater enjoys a high energy dissipation ratio with suitable hydraulic performance comparing with the conventional slit-type energy dissipaters.