阶梯—深潭系统消能机理试验研究
发布时间：2018-12-30 22:13
【摘要】：阶梯-深潭系统是山区河流常见的河床结构,具有稳定河床和消能减灾的作用。本研究以阶梯-深潭系统为研究对象,在对天然河流发育阶梯-深潭系统观测基础上,对阶梯-深潭系统的结构形态、水力特性和消能率展开研究,阐述了阶梯-深潭系统水流能量转化过程与消能机理,研究了推移质运动对阶梯-深潭系统消能的影响。通过对怒江、小江和雅鲁藏布江阶梯-深潭系统野外考察,将其按结构形态分为3类:三维阶梯-深潭、二维阶梯-深潭和二维三维之间阶梯-深潭,对各种形式结构特点进行总结,推荐三维阶梯-深潭作为典型阶梯-深潭。二维、三维阶梯-深潭系统消能对比试验验证了三维阶梯-深潭具有更高消能率,且随着流量增大二维阶梯-深潭消能率迅速降低,三维阶梯-深潭消能率降低缓慢,在高流量时仍能维持较高消能率。自然阶梯-深潭系统具有高消能率,本试验工况消能率为64%-91%。阶梯-深潭系统流场具有强三维性。阶梯与深潭水力特性相差大,阶梯上沿流向时均流速占主导,紊动弱;深潭中时均流速低,紊动强度高。试验工况下,阶梯上相对紊动强度约0.1,深潭中则最大超过8.0。深潭中雷诺应力是阶梯上约50倍。推导得到的阶梯-深潭消能率计算公式计算值与实测值符合较好。阶梯-深潭系统消能分为阶梯消能和深潭消能。水流能量转化分为3个过程:从阶梯跌落势能转化为时均动能;进入深潭时均动能转化为紊动能;紊动能耗散。由能谱和耗散谱分析知,水流进入阶梯-深潭后,能量由低频向高频转移,随着流量增大,深潭中紊动强度增大,能量耗散率增强,相比没有河床结构发育河段,阶梯-深潭系统更剧烈的将时均动能转化为紊动能,且具有更高耗散率。低流量时,阶梯消能占主导,随着流量增加,深潭消能作用逐渐增强,使阶梯-深潭始终保持高消能率,这是阶梯-深潭系统不同于其他河床结构的根本之处。山区河流能量消耗主要依靠推移质运动消能和河床结构消能。加沙试验显示,推移质运动的增强改变水流能量分配,其消能作用使阶梯-深潭结构消能降低,深潭於埋。推移质运动使阶梯上紊动与耗散略为增强,深潭中紊动与耗散大为减弱,从而使阶梯-深潭系统消能率降低。
[Abstract]:Ladder-deep pool system is a common river bed structure in mountainous area, which has the function of stabilizing river bed and reducing energy dissipation. Based on the observation of natural river development ladder deep pool system, the structure, hydraulic characteristics and energy dissipation rate of ladder deep pool system are studied in this paper. The energy transfer process and energy dissipation mechanism of stepped deep pool system are described. The effect of bed load motion on energy dissipation in stepped deep pool system is studied. Based on the field investigation of the Nu River, Xiaojiang River and Yalu Zangbo River stairs-deep pool system, they are divided into three categories according to their structure: three dimensional ladder deep pool, two dimensional ladder deep pool and two dimensional three dimensional ladder deep pool. This paper summarizes the characteristics of various forms of structure and recommends three-dimensional ladder-deep pool as a typical ladder-deep pool. The comparison test of energy dissipation in two dimensional and three dimensional ladder deep pool system proves that the three dimensional ladder deep pool has higher energy dissipation rate, and with the increase of flow rate, the energy dissipation ratio of two dimensional ladder deep pool decreases rapidly, and the energy dissipation rate of three dimensional ladder deep pool decreases slowly. High energy dissipation rate can be maintained at high flow rate. The natural ladder-deep pool system has high energy dissipation rate, and the energy dissipation rate in this test condition is 64-91. The flow field of the stepped-deep pool system is strongly three-dimensional. There is a big difference between the hydraulic characteristics of the ladder and the deep pool, the average velocity is dominant and the turbulence is weak, and the average velocity is low and the intensity of turbulence is high in the deep pool. Under the test conditions, the relative turbulence intensity on the ladder is about 0.1, and the maximum in the deep pool is more than 8.0. The Reynolds stress in the deep pool is about 50 times higher than that in the staircase. The calculated value of the energy dissipation rate formula derived from the step-deep pool is in good agreement with the measured value. Step-deep pool system energy dissipation is divided into step energy dissipation and deep pool energy dissipation. The energy conversion of water flow can be divided into three processes: from step drop potential energy to average kinetic energy, from average kinetic energy to turbulent energy when entering deep pool, and turbulent energy dissipation. According to the analysis of energy spectrum and dissipation spectrum, the energy transfer from low frequency to high frequency is obtained after the flow enters the staircase to deep pool. With the increase of flow rate, the turbulence intensity and energy dissipation rate in deep pool increase, compared with no river bed structure developed in river reach. The time-averaged kinetic energy is transformed into turbulent energy and the dissipation rate is higher in the stepped-deep pool system. With the increase of flow rate, the energy dissipation of deep pool is gradually enhanced, which makes the energy dissipation rate keep high, which is the fundamental point that the ladder-deep pool system is different from other river bed structure. The energy consumption of mountain rivers mainly depends on bed load motion energy dissipation and riverbed structure energy dissipation. The Gaza test shows that the enhancement of bed load movement changes the energy distribution of water flow, and its energy dissipation results in the decrease of energy dissipation of the stepped deep pool structure, and the deep pool is buried in the deep pool. The bed load motion increases the turbulence and dissipation slightly in the staircase, and weakens the turbulence and dissipation in the deep pool, thus reducing the energy dissipation rate of the stepped deep pool system.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV135.2
本文编号：2396235
[Abstract]:Ladder-deep pool system is a common river bed structure in mountainous area, which has the function of stabilizing river bed and reducing energy dissipation. Based on the observation of natural river development ladder deep pool system, the structure, hydraulic characteristics and energy dissipation rate of ladder deep pool system are studied in this paper. The energy transfer process and energy dissipation mechanism of stepped deep pool system are described. The effect of bed load motion on energy dissipation in stepped deep pool system is studied. Based on the field investigation of the Nu River, Xiaojiang River and Yalu Zangbo River stairs-deep pool system, they are divided into three categories according to their structure: three dimensional ladder deep pool, two dimensional ladder deep pool and two dimensional three dimensional ladder deep pool. This paper summarizes the characteristics of various forms of structure and recommends three-dimensional ladder-deep pool as a typical ladder-deep pool. The comparison test of energy dissipation in two dimensional and three dimensional ladder deep pool system proves that the three dimensional ladder deep pool has higher energy dissipation rate, and with the increase of flow rate, the energy dissipation ratio of two dimensional ladder deep pool decreases rapidly, and the energy dissipation rate of three dimensional ladder deep pool decreases slowly. High energy dissipation rate can be maintained at high flow rate. The natural ladder-deep pool system has high energy dissipation rate, and the energy dissipation rate in this test condition is 64-91. The flow field of the stepped-deep pool system is strongly three-dimensional. There is a big difference between the hydraulic characteristics of the ladder and the deep pool, the average velocity is dominant and the turbulence is weak, and the average velocity is low and the intensity of turbulence is high in the deep pool. Under the test conditions, the relative turbulence intensity on the ladder is about 0.1, and the maximum in the deep pool is more than 8.0. The Reynolds stress in the deep pool is about 50 times higher than that in the staircase. The calculated value of the energy dissipation rate formula derived from the step-deep pool is in good agreement with the measured value. Step-deep pool system energy dissipation is divided into step energy dissipation and deep pool energy dissipation. The energy conversion of water flow can be divided into three processes: from step drop potential energy to average kinetic energy, from average kinetic energy to turbulent energy when entering deep pool, and turbulent energy dissipation. According to the analysis of energy spectrum and dissipation spectrum, the energy transfer from low frequency to high frequency is obtained after the flow enters the staircase to deep pool. With the increase of flow rate, the turbulence intensity and energy dissipation rate in deep pool increase, compared with no river bed structure developed in river reach. The time-averaged kinetic energy is transformed into turbulent energy and the dissipation rate is higher in the stepped-deep pool system. With the increase of flow rate, the energy dissipation of deep pool is gradually enhanced, which makes the energy dissipation rate keep high, which is the fundamental point that the ladder-deep pool system is different from other river bed structure. The energy consumption of mountain rivers mainly depends on bed load motion energy dissipation and riverbed structure energy dissipation. The Gaza test shows that the enhancement of bed load movement changes the energy distribution of water flow, and its energy dissipation results in the decrease of energy dissipation of the stepped deep pool structure, and the deep pool is buried in the deep pool. The bed load motion increases the turbulence and dissipation slightly in the staircase, and weakens the turbulence and dissipation in the deep pool, thus reducing the energy dissipation rate of the stepped deep pool system.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV135.2
【参考文献】
相关期刊论文 前3条
1 季建清,钟大赉,丁林,张进江,杨逸畴;雅鲁藏布大峡谷地质成因[J];地学前缘;1999年04期
2 谭立新,许唯临,杨永全;泄水水垫塘内单位水体消能率的研究[J];水动力学研究与进展(A辑);2000年03期
3 余国安;王兆印;张康;王费新;;人工阶梯-深潭改善下切河流水生栖息地及生态的作用[J];水利学报;2008年02期
，本文编号：2396235
本文链接：https://www.wllwen.com/kejilunwen/shuiwenshuili/2396235.html
