陡槽侧墙和底板联合掺气水流特性研究

发布时间：2018-08-02 09:48

【摘要】：随着全球水利事业的高速发展,高速水流逐渐成为最值得关注的水力学科问题之一。陡槽中的高速水流容易形成局部低压区,这会有利于空化和空蚀的发生。为了避免空化和空蚀破坏的发生,施工工艺需严格控制建筑物过流边壁的不平整度,并选用设计优秀合理的建筑物体型,人为的在泄水建筑物中设置掺气设施,尽可能避免空蚀破坏以保护过流边壁。近年来,掺气设施一直具有经济、高效的优点。显然,全断面掺气比单独的底掺气和侧掺气要复杂,研究成果相对较少。本文将对底板和侧墙的联合掺气水流特性进行相关探究。本文通过陡槽模型试验,对不同体型的底掺气坎和侧掺气坎进行组合,形成联合掺气坎,研究陡槽全断面掺气水流特性。研究方法是通过对底、侧掺气坎坡度的变化、来流条件的变化,利用控制变量法分析各种影响因素对联合掺气坎的掺气空腔特性、坎后水流流态的影响,得出坎后掺气浓度的纵、横向分布规律和沿程衰减规律,探究联合掺气坎的掺气效率及掺气保护长度。通过试验研究和理论分析,本文得出了以下结论。首先,对于空腔特性而言：底空腔和侧空腔长度都与底坎坡比呈正相关；侧空腔长度与侧坎坡比呈正相关,但底空腔长度受到侧坎坡比的影响是微弱的。其次,对于掺气浓度的分布规律而言：沿程的分布呈现先增大后减小的规律,纵向先呈现底表大、中间小,后呈现自底而上逐渐增大的分布规律,横向分布呈现两侧大,中央小的规律。最后对于掺气浓度的影响因素,坎后水流的掺气浓度与侧坎坡比、底坎坡比、流量都呈正相关关系。相应的,底板和侧墙的掺气保护长度也都与底坎坡比、侧坎坡比和下泄流量呈正比关系的。但是掺气坎的坡度对流态的影响较大,特别是侧掺气坎坡度较大时容易使水流在坎后交汇时碰撞,形成较大水翅,使水流流态恶化。因此,体型尺寸良好的联合掺气坎才能获得好的流态和掺气效果,延长对陡槽的保护范围。试验研究表明：联合掺气坎对提高水流掺气浓度,保护边壁和底板不受到空蚀破坏是有利的。底掺气坎体型不仅影响了底空腔特性,也制约着侧空腔的形成。
[Abstract]:With the rapid development of global water conservancy, high-speed water flow has gradually become one of the most worthy of attention. The local low pressure region is easy to form in the high velocity flow in the steep channel, which is favorable for cavitation and cavitation erosion. In order to avoid cavitation and cavitation damage, the construction technology should strictly control the unevenness of the overflowing side wall of the building, select the excellent and reasonable design of the building shape, and set up the aeration facilities artificially in the drainage building. Avoid cavitation damage as much as possible to protect the flow side wall. In recent years, aeration facilities have been economic and efficient advantages. It is obvious that full section aeration is more complicated than single bottom aeration and lateral aeration, and the research results are relatively few. In this paper, the combined aeration flow characteristics of bottom slab and side wall are studied. In this paper, the combined aeration between the bottom aerator and the lateral aerator with different shapes is carried out to study the aeration flow characteristics of the whole section of the steep-trough by means of the model test of the steep-trough. The research method is to analyze the influence of various factors on the aeration cavity characteristics of the combined aerator and the water flow state after the combined aeration by using the control variable method through the change of the slope of the bottom and side aeration sill and the change of the incoming flow condition, and the control variable method is used to analyze the influence of various factors on the aeration cavity characteristics of the combined aerator. The longitudinal and lateral distribution and attenuation law of aeration concentration after the dam are obtained, and the aeration efficiency and the aeration protection length of the combined aerator are explored. Through experimental research and theoretical analysis, this paper draws the following conclusions. Firstly, the length of bottom cavity and side cavity are positively correlated with the ratio of bottom cavities and side cavities, and the length of side cavities is positively correlated with the ratio of side cavities to slope, but the influence of the length of bottom cavity on the ratio of side cavities to slope is weak. Secondly, for the distribution of aeration concentration, the distribution along the path increases first and then decreases. The longitudinal distribution presents the distribution law of large bottom surface, small middle, and gradually increasing from bottom to top, and the lateral distribution is large on both sides. A small central rule. Finally, for the influence factors of aeration concentration, there is a positive correlation between the aeration concentration and the side slope ratio, the bottom slope ratio and the flow rate. Accordingly, the aeration protection length of the bottom slab and side wall is proportional to the ratio of the bottom slope to the slope, the ratio of the side to the slope and the flow down. However, the gradient convection state of the aerator is more important, especially when the slope of the lateral aerator is high, the water flow will easily collide at the intersection behind the ridge, resulting in the formation of larger water wings, and the deterioration of the water flow state. Therefore, the better flow state and aeration effect can be obtained by the combination aerator with good size, and the protection range of the steep trough can be extended. The experimental results show that the combined aerator can improve the aeration concentration of water flow and protect the side wall and bottom plate from cavitation erosion. The shape of bottom aerator not only affects the characteristics of bottom cavity, but also restricts the formation of side cavity.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV135.2;TV131.34

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