Experimental Study of Flow Field in Asymmetric Compound Channel with Diverging and Inclined Floodplains

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of Flow Field in Asymmetric Compound Channel with Diverging and Inclined Floodplains

ارائه دهنده: Provider: Amin Kohzadi

اساتید راهنما: Supervisors: Bahram Rezaei (Ph. D)

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: (Ph. D)Jalal Sadeghiyan (Ph. D)- Jalal Akbari

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

مکان ارائه: Place of presentation: 43

چکیده: Abstract: ompound Channels refer to hydraulic systems consisting of a main channel and one or more adjacent floodplains. These types of channels exhibit complex flow patterns due to the differences in depth and roughness between the main channel and the floodplain. In asymmetric compound channels with divergent floodplains, unconventional geometric conditions, such as varying floodplain widths and angles relative to the main flow axis, create more complex hydrodynamic behavior. Divergence leads to flow expansion, velocity reduction, and pressure variations, directly affecting flow patterns, sediment transport, and bed shear stress distribution. These characteristics make the study of flow in asymmetric divergent compound channels a challenging yet critical topic for designing hydraulic structures, flood management, and predicting erosion and sediment deposition phenomena. Accurate analysis of these systems requires numerical and experimental models to describe the complex behavior of secondary flows, flow separation, and mixing in boundary regions. In this study, the flow field in an asymmetric compound channel with divergent sloped floodplains, with divergence angles of 3.81 and 11.31 degrees, was investigated experimentally. The experiments included measurements of velocity distribution, boundary shear stress, water surface profiles, and flow discharge distribution. The results showed that at the beginning of the divergent region near the boundary between the main channel and the floodplain, the velocity reached its maximum value. However, as the flow moved along the divergent region, the velocity decreased. Along the divergent region, with an increase in relative flow depth, the percentage of flow passing through the main channel decreased, while the percentage of flow passing through the divergent floodplain increased. Furthermore, with an increase in the divergence angle of the floodplain, the percentage of flow passing through the divergent floodplain increased. The transverse distribution of shear stress in asymmetric compound channels with divergent floodplains was similar to the transverse distribution of depth-averaged velocity. Boundary shear stress in the main channel was always greater than that in the divergent floodplain. Analysis of water surface profiles showed that at the entrance of the divergent region, the water surface profile was relatively uniform. However, along the divergent region, due to changes in flow velocity and the presence of secondary flows, the water surface profile became non-uniform. Additionally, as the flow velocity in the main channel was greater than in the floodplain, this velocity difference created momentum and pressure gradients, eventually forming secondary flows. Depending on the direction of the pressure gradient, the geometric asymmetry of the channel further complicated the secondary flows.

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