Secondary Flow Characteristics in Meandering Compound Channels with One-sided Floodplain Vegetation
To investigate the impact of one-sided floodplain vegetation on secondary flow in meandering channel,we designed meandering compound channels with smooth floodplains and one-sided vegetated floodplains in a general-ized manner,and measured the cross-sectional instantaneous velocities using an Acoustic Doppler Velocimeter(ADV).The experimental results revealed that the formation of main vortexes in a single bend is solely influenced by centrifugal force,whereas the formation of main vortexes in the experimental meandering compound channel is closely associated with flow exchange between the floodplains and the main channel.When the relative water depth is 0.15,compared to the situation under smooth floodplain conditions,the secondary flow intensities at the apex sections with the narrowest vegetated floodplain and in crossover areas exhibit larger attenuation,but there is no ap-parent difference for the secondary flow intensity at apex section with the widest vegetated floodplain.For the rela-tive depth of 0.35,the secondary flow intensity at each cross section in the meandering channel is enhanced,with the secondary flow intensity under one-sided vegetated floodplain conditions being smaller than the corresponding value under smooth floodplain conditions.In the case of one-sided vegetated floodplain conditions and the same rel-ative depth,the secondary flow intensities in the crossover areas with a smooth upstream floodplain are notably lar-ger than the corresponding values in crossover areas with a vegetated upstream floodplain.Under the smooth flood-plain conditions,the"island center"of the cross-sectional contours of Reynolds stress Rvw can indicate the rotation-al center of the main vortex.The positive or negative sign of the Reynolds stress Rvw at the"island center"can re-flect the rotational direction of the main vortex.Conversely,under the one-sided vegetated floodplain conditions,the Rvw contours in the cross-sectional middle parts appear disordered and do not demonstrate the aforementioned characteristics,with the absolute values of Reynolds stress Rvw being noticeably smaller than the corresponding val-ues under smooth floodplain conditions.
国家科技期刊平台
NSTL
万方数据
