Experimental Study of the Effect of Floodplain width on Flow Field in Prismatic Compound Channels with Inclined Floodplains

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of the Effect of Floodplain width on Flow Field in Prismatic Compound Channels with Inclined Floodplains

ارائه دهنده: Provider: Mohammad Aref Zangane

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

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees:

زمان و تاریخ ارائه: Time and date of presentation: September, 09, 2020

مکان ارائه: Place of presentation:

چکیده: Abstract: In compound channels, due to the difference in flow velocity in the main channel and the floodplains, an apparent shear stress occurs inside the fluid layers, which causes mass and momentum transfer. In compound channels with divergent floodplains, changes in the geometry of the floodplains lead to the exchange of excess momentum and turbulence between the main channel and the floodplain, and have a significant effect on the hydraulic flow. So far, various characteristics of a compound channel have been studied both numerically and in laboratory models; However, the study of sloping floodplains has been done in small numbers, so the need for this study and research is clear. To investigate the effects of width change on the flow field in prismatic compound channels with sloping floodplains, velocity and shear stress measurements were made. Then, using mathematical and statistical methods, the data obtained from laboratory operations were analyzed to conclude what effects the change in width can have on the flow field of a prismatic compound channel. Finally, the results of this study showed that the maximum velocity in the cross section of the compound channel with oblique floodplains is not formed in the center of the channel. Rather, the site of maximum velocity formation is near floodplains. However, the slope of the floodplains alone can not lead to such a thing. Whereas if water flows at a relatively low depth on a compound channel, since the amount of water on the floodplains is not large enough to change the flow of water on the main canal; So the same maximum velocity occurs in the center of the main channel. Increasing the channel width increases the average value of the manning coefficient. By doubling the width of the floodplains, the discharge capacity on them also increases; In some cases, it doubles to a maximum. The maximum shear stress is not formed in the center of the main channel; Rather, like velocity, it happened near oblique floodplains. As the relative depth of the flow increases; The amount of shear stress in the main channel is reduced and added to the amount of shear stress on the floodplain. Increasing the width of floodplains reduces the average shear stress of the wall and also increases the share of shear stress of floodplains. As the width of the floodplains increases, the shear force changes on the walls of the main channel and the floodplains decrease and remain almost constant. Key Words: compound channel, Sloping Floodplain, prismatic compound channel, velocity distribution, shear stress.

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