窄深水域强紊动射流实验研究

Energy loss by jet diffusion in confined jets can be effective within short distances from the jet exit. Engineering applications are mostly associated with energy dissipators in releasing flood structure, sewer manholes and dissipation chambers of drop shafts in urban drainage systems, and fish passage structure in ecological engineering. However, there is little literatures about the confined strong turbulent jets into narrow and deep waters. Based on theory of turbulent circular and rectangular jets, velocity, air concentration, pressure, cavitation will are measured Synchronously and Automatically by using measurement systems developed our own in physical models. Characteristics of hydraulic will be observed with the jet shape and boundary conditions. distributions of velocity and pressure and concentration will be measured for analyzing the variation law of hydraulic parameters. LES turbulent model will be used to numerically simulate the flow field and pressure field and turbulent kinetic energy. The calculated results will be compared with the experimental data and verify them. The formula to calculate the velocity and pressure and concentration will be derived for prediction of them. The critic condition to aerate in flows will be presented. Mechanics of aeration flows and cavitation will be discussed. Applications and theories of confined strong turbulent jets will be shown in this research reports.

强紊动射流在水电工程的泄洪消能建筑物、城乡排水系统的沙井和跌井、生态系统的鱼道、生态流量放水设施的消能设计中应用十分广泛。但是，强紊动射流在窄深水域的流动特性研究较少。本课题基于有界域圆形和矩形强紊动射流理论；设计和运用能够同步测量流场、浓度场、压力场、空化噪声的自动采集实验测试系统；观测射流出口形状、边界参数对水力特性的影响；获得流速衰减规律，特别是掺气浓度场、压力场及紊动掺混特性、空化特性的变化规律；运用LES紊流数学模型，计算不同射流形状、边界参数条件下窄深水域流场、压力场、浓度场和紊动能及其耗散率分布；经实验验证后，结合理论分析成果，推导出速度衰减计算公式，壁面压力沿程分布及计算方法，掺气浓度分布及其计算方法；提出初始掺气临界条件，揭示掺气减蚀作用与机制，论证空化特性；深入分析速度衰减规律、紊动能分布和紊动能耗散率分布规律，探讨消能机理；为实际应用提供理论和实验依据。

强紊动射流在水电工程的泄洪消能建筑物、城乡排水系统的沙井和跌井、生态系统的鱼道、生态流量放水设施的消能设计中应用十分广泛。本课题针对强紊动射流在窄深水域的流动特性展开系统实验研究和数值模拟研究；分析了射流出口形状、边界参数对流场、浓度场、压力场的影响；获得了流速衰减规律以及掺气浓度场、压力场及紊动掺混特性、空化特性的变化规律；计算获得紊动能及其耗散率分布；建立了速度衰减计算公式，壁面压力沿程分布及计算方法，掺气浓度分布及其计算方法。.（1）矩形、圆形射流流速扩散衰减对比结果表明：圆形射流主流方向上流速衰减速率比矩形射流是快还是慢，主要取决于矩形射流的高宽比；宽扁型矩形射流出口的射流主体在射流出口中心线上下摆动最剧烈，且摆动位置比窄深型矩形射流和圆形射流更靠近射流出口；矩形、圆形射流在横向和垂向上的流速衰减规律差别较大。.（2）通过对比分析圆形射流和矩形射流的消力池底板脉动压力的影响可得出：圆形射流在消力池底板脉动强度系数较宽扁型矩形射流（a/b=1/2）小，比窄深型（a/b=4）大。圆形射流较宽扁型矩形射流具有脉动压力强度小，受Fr和淹没度变化影响较小；而圆形射流较窄深型矩形射流脉动压力强度偏大，受Fr和淹没度变化影响也较大。在体型参数和水力学参数相同的情况下，Fr越大水流紊动越剧烈，小尺度的漩涡越多。圆形和矩形射流底板脉动压力最大值点相关性均是随着Fr的增加而减小；.（3）圆形射流和矩形射流消力池底板水流漩涡的尺度和漩涡能量与淹没度并非单纯的单调关系。圆形射流和矩形射流受淹没度的影响规律存在较大差异，圆形射流受淹没度影响较小，矩形射流随高宽比的偏离程度越大影响也越大。.研究表明，圆形射流与矩形射流相比，具有流速衰减速率快，在水体扩散过程中的稳定性较好，底部的冲击压力脉动强度小和掺气浓度相对较为均匀，在实际工程中有更好的适用性和安全性。