Experimental Study of Flow Field in Non-Prismatic Compound Channel with Converging Inclined Floodplains

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of Flow Field in Non-Prismatic Compound Channel with Converging Inclined Floodplains

ارائه دهنده: Provider: Mohammad Reza Mihani

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

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: دکتر جلال صادقیان دکتر مجید فضلی

زمان و تاریخ ارائه: Time and date of presentation: November, 14, 2020

مکان ارائه: Place of presentation:

چکیده: Abstract: Rivers are constantly changing their bed and banks, and this causes their path to change fundamentally over time. Continuous change and transfiguration is one of the principles governing any river in which, along with the movement and flow of water and sediment in the bed, changes and displacements occur in other geometric characteristics of the river. Changes in the steady state of the river will lead to new interactions and consecutive changes in the physical characteristics of the river. Compound channels form the cross section of many rivers. Investigation of hydraulic behavior of compound channels is very important in flood control plans and river training. The flow velocity in the main channel of the river is higher than the floodplains due to its great depth and less roughness, while the flow in the floodplains is much slower due to its shallow depth and greater roughness. This difference in velocity between the main channel and the floodplains creates a significant lateral gradient, so a shear layer will form at the interface between the two sections. This shear layer creates shear stress in addition to the shear stress of the bed and channel walls, which is called apparent shear stress. Due to presence of this shear layer, vortices with the vertical axes and in the direction of flow appear. As the flow depth on the floodplains increases, the distance between these vortices and their dimensions gradually decreases, and in practice a continual interaction zone is created uniformly at the interface between the main channel and the floodplains. This process causes a continuous mass and momentum exchange between the main channel and the floodplains. In this study, the effect of different convergence angles of floodplains with the same lateral slope on the hydraulic of flow in non-prismatic compound channel has been investigated experimentally. For this purpose, various experiments have been performed at three relative depths (0.3, 0.4 and 0.5) for convergence angles of 3.81 ° and 11.31 °. The experiments included measuring the water surface profile, velocity distribution, depth-averaged velocity distribution, boundary shear stress distributions and the results were reported in graphical and tabulated form. The velocity distribution at different cross-sections along the convergence zone were measured using a Acoustic Doppler Velocimeter (ADV) and boundary shear stresses were also measured using a Preston tube having a 4mm outer diameter. The results show that increasing the convergence angle and relative depth will cause a change in the hydraulic of flow so that at a certain relative depth, the amount of increase in velocity and boundary shear stress along the convergence length increases with increasing convergence angle. Key Words: Non-Prismatic Compound Channel, Floodplain, Boundary Shear Stress, Flow Field, Converging, Secondary Flow

فایل: ّFile: Download فایل