Experimental Study of The Effect of Vegetation on The Flow Field in Asymmetric Compound Channel with Diverging and Inclined Floodplain

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of The Effect of Vegetation on The Flow Field in Asymmetric Compound Channel with Diverging and Inclined Floodplain

ارائه دهنده: Provider: Saeed Roohi

اساتید راهنما: Supervisors: Dr Bahram Rezaei

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr Jalal Akbari - Dr Jalal Sadeghian

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: 43

چکیده: Abstract: Abstract: During a flood in river, if the main channel is unable to carry the flood discharge, excess flow leaves the main channel and enters the floodplains. Due to topographic conditions, rivers are often simulated as non-prismatic compound channels. In non-prismatic compound channels, due to the effect of mass and momentum exchange between the main channel and floodplains, flow structure is more complex than prismatic compound channels. As a result, research into the flow characteristics in non-prismatic compound channels can help hydraulic engineers better understand the flow behavior in river flow during flood. In this research, the effects of rigid vegetation on the flow field in asymmetric compound channels with inclined [lateral slope 0.075) and diverging floodplain (diverging angle of 11.31o and 3.81o) and three relative depths of 0.3, 0.4 and 0.5 was experimentally investigated. Using experimental data , velocity distribution, bed shear stress , precentage of discharge in the main channel and diverging floodplain, secondary flows, and water surface profile were investigated. Furthermore, in some stages, experimental data were compared with research of asymmetric compound channel , with similar geometry without vegetation (Kohzadi, 2025). Result analysis indicates that at the beginning of diverging part of the flume, the velocity and the bed shear stress have the maximum values. By moving along diverging part of the flume, the velocity and the shear stress decrease. The deformation and curvature of the isovel lines indicate presence of two local peaks near the main channel walls. By increasing relative depth and the floodplain divergence anlgels, the depth-averaged velocity in the main channel and floodplain increases, but this increase is not significant in the floodplain due to the presence of vegetation Studies show nonlinear distributions of the percentage of discharges in the main channel and floodplain along the non-prismatic part of the flume. Also, by increasing relative depth, the percentage of discharge in the main channel decreases but increases on the diverging floodplain. Similar to the depth-averaged velocity distribution, the bed shear stress in the main channel is greater than that on the diverging floodplain. By increasing relative depth, the bed shear stress in main channel and on the vegetated diverging floodplain increased. A comparison between the results of this research with the experimental data of Kohzadi (2025) shows that the presence of vegetation in the divergent floodplain increases the velocity and bed shear stress in the main channel and reduces them on the diverging floodplain. Key Words: Asymmetric compound channel, diverging floodplain, vegetation, velocity distribution, bed shear stress.

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