变流速比与宽度比条件下分汊河道分层流紊动特性

针对目前分汊河道分层流紊动特性研究的空白，通过物理模型试验探索分汊河道温差剪切分层流在不同上下层速度比与汊道宽度比影响下的紊动强度变化规律。结果表明:随着上下层流速比由大变小，汊道分层流发生从分层到混合的转捩。在混合流条件下，支汊沿程断面高紊动区由C形分布转变为倒C形分布，最终全断面紊动分布均匀；随着支汊宽度增大，高紊动区出现的断面位置呈现滞后性，且紊动能量值增大。其他分层流态条件下，强紊动能分布的范围和量值都有所变化。对于交汇口断面，对称汊道在断面中心处掺混剧烈，随着上下层流速比的增大，紊动能量值减小；不对称汊道出口断面紊动强烈区域向较窄的左支汊一侧移动，与岛屿尾尖位置密切相关。

Turbulence characteristics of stratified flow in braided river with varied velocity ratios and width ratios

At present, few studies have been conducted on turbulence characteristics of stratified flow in braided rivers. In this study, a physical model experiment was carried out to study the variation of the turbulent intensity of thermally stratified shear flow with different velocity ratios of two layers and width ratios of two anabranches. The results show that, as the velocity ratio decreased, the stratified flow in the braided river changed from stratified flow to neutrally stratified flow. As to the neutrally stratified flow, the sectional high-turbulence zone along the anabranches changed from a C-type distribution to an inverse C-type distribution, and the turbulent intensity was mixed well throughout the section in the end. With the increase of the channel width, the section of the high-turbulence zone appeared later, and the quantity of the turbulent intensity increased. Under other conditions of stratified flow, the range and quantity of high turbulent intensity all changed. At the confluence section, the flow in the center of the section was mixed violently in the symmetric braided river. With the increase of the velocity ratio, the quantity of the turbulent intensity decreased. The high turbulent intensity zone moved to the narrowed left anabranch in the non-symmetric braided river, which was associated with the tail position of the mid-bar.