低Froud数跌坎型底流消能工不同水流结构区掺气特性研究
发布时间：2018-09-10 12:56
【摘要】：近年来我国水利水电事业迅速发展,新建了许多大型水利水电工程,这些工程往往具有高水头、大流量的特点,泄洪消能问题较为突出,许多地质条件差,对环境要求高的在建和将建工程都放弃了挑流消能方案而选择底流消能。 基于底流消能的跌坎型消能工是一种能适应高水头、大流量的新型消能工。由于跌坎的存在,水流进入消力池后,沿程得到一定程度的扩散,主流两侧形成漩涡以及强烈的紊动剪切扩散,将高速的主流引离临底区域,临底流速有效降低,因此基于底流消能的跌坎型底流消能工,具有消能率高、入池流态稳定,对地质条件适应性强以及水流雾化小等优点,该消能工具有较好的应用前景。由于入射水流与消力池内水体形成紊动剧烈的剪切面,导致大量空气被卷吸入水中形成水气两相流,气泡存在于水流紊流流场中时,原来的紊流结构势必会发生变化,气泡和水流之间的流动形态将存在明显的差异,如气泡跟随性的强弱决定了水气两相之间的流速差,气泡的存在使得水体膨胀,水深增加,同时也会增大水流脉动,增加建筑物的瞬时荷载,另外还会引起水流附加紊动耗散,因而掺气浓度的大小及其分布规律必将影响到消力池内临底流速、压强,消力池内水深以及消能率等水力因素。对于掺气水流的研究,无疑能能帮助人们更好的认识跌坎型底流消能工中各水力因素间的关系,对优化跌坎型底流消能工体型设计有着重要意义。 本文是基于国家自然科学基金(项目编号：51169008)而立题,采用水力学试验的方法,测量了入池Froud数为3.09至5.41时,跌坎型底流消能工在不同流量、跌坎深度以及入射角度下,不同水流结构区的流速、底板压强、掺气浓度值,并通过对比分析得到入池流量、跌坎深度以及入射角度对不同水流结构区掺气浓度沿程分布的影响规律以及水体中气泡迁移扩散的运动机理。
[Abstract]:In recent years, with the rapid development of water conservancy and hydropower industry in China, many large water conservancy and hydropower projects have been built. These projects often have the characteristics of high water head and large discharge, the problem of flood discharge and energy dissipation is prominent, and many geological conditions are poor. Both the construction and the construction project with high environmental requirements have abandoned the energy dissipation scheme and opted for the energy dissipation at the bottom flow. The energy dissipator based on bottom flow is a new type of energy dissipator with high water head and high flow rate. Because of the existence of the fall, the flow into the stilling pool, along the course to a certain extent of diffusion, the formation of vortex on both sides of the mainstream and strong turbulent shear diffusion, leading the high-speed mainstream away from the near bottom area, the near bottom velocity is effectively reduced, Therefore, the energy dissipation tool based on the bottom flow energy dissipation has the advantages of high energy dissipation rate, stable flow state in the pool, strong adaptability to geological conditions and small atomization of water flow, etc. The energy dissipation tool has a good prospect of application. Due to the turbulent shear surface between the incident water flow and the water body in the stilling pool, a large amount of air is swept into the water to form a two-phase water vapor flow. When bubbles exist in the turbulent flow field, the original turbulent structure is bound to change. There will be obvious differences in the flow patterns between the bubbles and the water flow. For example, the velocity difference between the two phases of water and gas is determined by the strength of the bubble's following property. The existence of the bubble causes the water body to expand, the water depth increases, and the flow pulsation is also increased. Increasing the instantaneous load of the building will also cause additional turbulent dissipation of water flow. Therefore, the magnitude of aeration concentration and its distribution law will affect the hydraulic factors such as the near bottom velocity, pressure, water depth and energy dissipation rate in the stilling tank. The study of aerated flow can undoubtedly help people to better understand the relationship between hydraulic factors in the energy dissipators of the floor flow, and it is of great significance to optimize the design of the energy dissipators of the floor flow. This paper is based on the National Natural Science Foundation of China (item No.: 51169008), using the method of hydraulics test, measuring the Froud number of the entering pool from 3.09 to 5.41, and measuring the energy dissipators with different flow, depth and angle of incidence under the condition of different flow, depth and angle of incidence. The velocity of flow, the pressure of bottom plate, the concentration of aeration in different flow structure areas are obtained, and the flow into the tank is obtained by comparison and analysis. The influence of the depth and the incident angle on the distribution of aeration concentration in different flow structures and the movement mechanism of bubble migration and diffusion in water are discussed.
【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
本文编号：2234504
[Abstract]:In recent years, with the rapid development of water conservancy and hydropower industry in China, many large water conservancy and hydropower projects have been built. These projects often have the characteristics of high water head and large discharge, the problem of flood discharge and energy dissipation is prominent, and many geological conditions are poor. Both the construction and the construction project with high environmental requirements have abandoned the energy dissipation scheme and opted for the energy dissipation at the bottom flow. The energy dissipator based on bottom flow is a new type of energy dissipator with high water head and high flow rate. Because of the existence of the fall, the flow into the stilling pool, along the course to a certain extent of diffusion, the formation of vortex on both sides of the mainstream and strong turbulent shear diffusion, leading the high-speed mainstream away from the near bottom area, the near bottom velocity is effectively reduced, Therefore, the energy dissipation tool based on the bottom flow energy dissipation has the advantages of high energy dissipation rate, stable flow state in the pool, strong adaptability to geological conditions and small atomization of water flow, etc. The energy dissipation tool has a good prospect of application. Due to the turbulent shear surface between the incident water flow and the water body in the stilling pool, a large amount of air is swept into the water to form a two-phase water vapor flow. When bubbles exist in the turbulent flow field, the original turbulent structure is bound to change. There will be obvious differences in the flow patterns between the bubbles and the water flow. For example, the velocity difference between the two phases of water and gas is determined by the strength of the bubble's following property. The existence of the bubble causes the water body to expand, the water depth increases, and the flow pulsation is also increased. Increasing the instantaneous load of the building will also cause additional turbulent dissipation of water flow. Therefore, the magnitude of aeration concentration and its distribution law will affect the hydraulic factors such as the near bottom velocity, pressure, water depth and energy dissipation rate in the stilling tank. The study of aerated flow can undoubtedly help people to better understand the relationship between hydraulic factors in the energy dissipators of the floor flow, and it is of great significance to optimize the design of the energy dissipators of the floor flow. This paper is based on the National Natural Science Foundation of China (item No.: 51169008), using the method of hydraulics test, measuring the Froud number of the entering pool from 3.09 to 5.41, and measuring the energy dissipators with different flow, depth and angle of incidence under the condition of different flow, depth and angle of incidence. The velocity of flow, the pressure of bottom plate, the concentration of aeration in different flow structure areas are obtained, and the flow into the tank is obtained by comparison and analysis. The influence of the depth and the incident angle on the distribution of aeration concentration in different flow structures and the movement mechanism of bubble migration and diffusion in water are discussed.
【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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