出水口位置对异重流特性及泥沙分布的影响

发布时间：2018-03-11 06:49

本文选题：间层流　切入点：分层水库　出处：《西安建筑科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：地下水资源的匮乏导致水库逐渐成为城市用水的主要水源。夏季暴雨及冬季寒流引发的强降雨会造成高泥沙含量和高污染负荷暴雨径流进入水库,在一定条件下形成异重流。深水型水库易于夏季形成正向水温分层。本文利用自制的分层模型水库,开展了不同入流泥沙粒径、入流泥沙浓度和出水口位置条件下的异重流中试研究,主要研究出水口位置对异重流泥沙分布、特性参数和排沙比的影响。主要研究成果如下:在弱分层水体中,固定入流流量0.324m3/h,当入流泥沙浓度分别为1.25g/L、3.75g/L、7.5g/L,出水口位置分别距库底38.5cm、18cm、4cm时,入流泥沙粒径0.01mm和0.05mm条件下异重流运动特性类似,泥沙浓度分布、排沙比以及特性参数差异较小。在强、弱分层水体中,异重流均表现为间层流;当入流泥沙浓度相同时,出水口分别位于上、中、下层,异重流厚度、分离点深度、水跃高度和行进时间等参数数值相近;在入流泥沙浓度固定的条件下,当出水口位于上层时,异重流以间层流形式直接水平流出库外,间层流厚度基本沿程不变;当出水口位于中下层时,间层流运动至出水口断面后会卷吸周围清水,引起间层流厚度局部增加。对比分析了强、弱分层条件下泥沙浓度和水温分布情况,当入流泥沙浓度确定时,如出水口位于上层,跃温层不会发生下潜现象;如出水口位于中、下层,跃温层会发生下潜现象,并且出水口位于下层时下潜最严重;在其他条件相同时,跃温层下潜在弱分层水体中更为严重。在弱分层水体中,异重流排沙比受出水口位置和入流泥沙浓度共同影响。对于上层出水口,入流泥沙浓度1.25g/L时的排沙比大于3.75g/L时的对应值;对于中层出口,入流泥沙浓度1.25g/L与3.75g/L时的排沙比相差不大;对于下层出水口,排沙比变化特性与上层出水口相反。如入流泥沙浓度较小,上层出水口时的排沙比大于中、下层对应值;如入流泥沙浓度较大,中层出水口时的排沙比大于上、下层出水口对应值。在强分层水体中,如出水口位置确定,则入流泥沙浓度基本不影响异重流排沙比;如入流泥沙浓度确定,则上层出水口时的排沙比远远大于中、下层出水口对应值。随着异重流运动时间延长,虽然排沙比有所增加,但库区掺混严重,并不利于排沙。
[Abstract]:The scarcity of groundwater resources leads to the reservoir gradually becoming the main water source for urban water. Heavy rainfall caused by heavy rain in summer and cold current in winter will cause heavy rain runoff with high sediment content and high pollution load to enter the reservoir. Under certain conditions, the gravity flow is formed. The deep water reservoir is apt to form the forward water temperature stratification in summer. In this paper, different sediment particle sizes are developed by using the self-made stratified model reservoir. The effects of the location of the outlet on the distribution, characteristic parameters and the ratio of sediment discharge of the dense flow are studied. The main results are as follows: in the weakly stratified water body, the main results are as follows: in the weak stratified water body, the distribution of sediment, the characteristic parameters and the ratio of sediment discharge are studied. When the inlet sediment concentration is 1.25g / L 3.75g / L 7.5g / L and the outlet position is 38.5 cm ~ (-1) cm ~ (-1) ~ 4 cm ~ (-1) from the bottom of the reservoir, the density distribution, sediment discharge ratio and characteristic parameters are similar under the conditions of 0.01mm and 0.05mm grain size. The difference of sediment concentration distribution, sediment discharge ratio and characteristic parameters is small. In the weakly stratified water body, the density current is interlaminar flow, when the sediment concentration is the same, the outlet is located in the upper, middle, lower layer, density current thickness, the depth of separation point, the water jump height and the travel time and so on. When the inlet sediment concentration is fixed, when the outlet is in the upper layer, the density current flows out of the reservoir directly in the form of interlaminar flow, the thickness of the interlaminar flow is basically unchanged, and when the outlet is located in the middle and lower layers, When the interlaminar flow is moved to the section of the outlet, the surrounding water will be sucked in, which will cause the local increase of the interlaminar flow thickness. The distribution of sediment concentration and water temperature under the condition of strong and weak stratification is compared and analyzed. When the inlet sediment concentration is determined, if the outlet is located in the upper layer, If the outlet is in the middle, the lower layer, the temperature jump layer will submerge, and when the outlet is in the lower layer, the dive will be the most serious; when other conditions are the same, In the weakly stratified water body, the ratio of heavy current to sediment discharge is affected by the location of outlet and the concentration of sediment. For the upper outlet, it is more serious in the potentially weakly stratified water body under the temperature jump layer. The sediment discharge ratio at 1.25g / L of incoming sediment concentration is greater than the corresponding value at 3.75g / L; for the middle outlet, the ratio of sediment discharge at 1.25g / L and 3.75g / L is not significant; for the lower outlet, The variation of sediment discharge ratio is opposite to that of the upper outlet. If the sediment concentration in the upper outlet is small, the sediment discharge ratio at the upper outlet is greater than that in the middle and the lower layer, and the sediment discharge ratio at the middle outlet is greater than that at the middle outlet if the sediment concentration is larger than that at the middle outlet. In the strong stratified water body, if the location of the outlet is determined, the sediment concentration in the inlet flow will not affect the sediment discharge ratio of the gravity current basically; if the sediment concentration in the upper layer is determined, the sediment discharge ratio of the upper outlet will be far greater than that of the middle one. With the extension of the gravity current movement time, the sediment discharge ratio increased, but the mixing in the reservoir area was serious, which was not conducive to sediment discharge.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV145

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