The presence of vegetation on the floodplains of compound channels affects the structure of mean flow, increases flow resistance and turbulence intensity, and impacts sediment transport. In prismatic compound channels, the shear stress at the interface between the flows in the main channel and lateral floodplains has a strong influence in the cross sectional velocity distribution and thus conveyance of the channel. Due to mass transfer between subsections, these effects are enhanced in non‐prismatic channels. In the present study, the three‐dimensional turbulent flow structure in a vegetated non‐prismatic convergent compound channel is experimentally investigated. The main purpose is to clarify the explicit influence of the combination of two factors (floodplain vegetation and convergent floodplains) on mean flow and large‐scale turbulence. The experiments were conducted for relative depths (i.e., the ratio between floodplain and main channel flow depths) equal to 0.21 and 0.31 and floodplain convergence angles equal to 7.25° and 11.3°. The results obtained in straight compound channel with vegetated floodplains were used as a reference. The analysis of the Acoustic Doppler Velocimeter measurements shows that due to convergent floodplains, a transverse current is directed from the floodplains to the main channel from both sides, generating two helical secondary currents. Investigations of the vegetation influence on Reynolds stresses shows that there is a significant vertical and lateral spreading of the shear region towards the main channel side slope. As the convergence angle increases, the floodplain flow proportion decreases. In this case, the presence of vegetation in the floodplain leads to a suppression of the momentum exchange between main channel and floodplains causing the discharge distribution between sub‐sections to be significantly different from what would be without floodplain vegetation.

中文翻译：

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植被非棱柱复合通道中的湍流结构

复合河道漫滩上植被的存在影响了平均流量的结构，增加了流动阻力和湍流强度，并影响了沉积物的输送。在棱柱形复合通道中，主通道和横向洪泛区之间的流动界面处的剪切应力对截面速度分布以及通道的输送有很大的影响。由于各小节之间的传质，这些影响在非棱柱形通道中得到增强。在本研究中，通过实验研究了植被非棱柱形收敛复合通道中的三维湍流结构。主要目的是弄清两个因素（洪泛区植被和会聚洪泛区）的组合对平均流量和大尺度湍流的显着影响。进行了相对深度（即洪泛区与主河道水深之比）等于0.21和0.31以及洪泛区会聚角等于7.25°和11.3°的实验。在带植被泛滥平原的直复合河道中获得的结果用作参考。声学多普勒测速仪测量结果的分析表明，由于洪泛区的收敛，横向电流从洪泛区的两侧被引导至主通道，从而产生了两个螺旋形的次级电流。对植被对雷诺应力的影响的调查表明，剪切区域朝着主河道边坡有明显的垂直和横向扩展。随着会聚角的增加，洪泛区流量比例减小。在这种情况下，