Experimental Study of Flow in Skewed Compound Channel with Inclined Floodplains

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of Flow in Skewed Compound Channel with Inclined Floodplains

ارائه دهنده: Provider: Mostafa Dolati Mahtaj

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: March, 15, 2021 – 10:30 AM

مکان ارائه: Place of presentation: دپارتمان مهندسی عمران

چکیده: Abstract: During a flood in rivers, if the main section of the river is not able to transfer the flood, flow leaves the main channel and enters the floodplains. Due to the influence of local topographic conditions, rivers with a straight compound section rarely found in nature and most rivers have a non-prismatic cross-section. In non-prismatic compound channels, because of the effect of changing in cross-section along the channel, the flow structure is more complex than prismatic compound channels. Therefore, it is important to study the flow characteristics in such channels and it can help engineers to better understand the flow behavior in rivers, especially during floods. In the present study, the flow behavior in skewed compound channels with inclined floodplains has been investigated experimentally. In these channels, one of the floodplains is diverging and the other is converging. The experiments were performed at three relative depth of 0.2, 0.3 and 0.4 and for two skewed angles of 3.81o and 11.31o. Measurements were performed along the skewed area in 5 section with 1.5 m longitudinal intervals for the compound channel with the skewed angle of 3.81o and in 3 section by 1 m longitudinal intervals for the compound channel with the skewed angle of 11.31o. The purpose of these measurements was to investigate the effect of the angle of skewed floodplains and also their lateral slope on the flow characteristics in skewed compound channels. By using the experimental data, the lateral distribution of flow velocity, boundary shear stress, flow rate distribution, secondary flows, water surface profile and flow resistance have been investigated. According to the results, the lateral distribution of flow velocity and boundary shear stress in skewed compound channels with inclined floodplains is asymmetric and non-uniform. Also, the flow velocity and boundary shear stress in the diverging floodplain is always higher than their values in converging floodplain. By increasing the skew angle of the floodplains, the flow velocity and boundary shear stress in the whole cross-section of the channel, especially in floodplains, have increased. Also, by increasing the floodplains skew angle, the magnitude of secondary flows increases and the uniformity of the water surface profile decreases. Because of the floodplain lateral slope, the velocity and boundary shear stress in the diverging floodplain increase while their values in the converging floodplain decrease. This point has caused to increase of non-uniformity in the lateral distribution of velocity and boundary shear stress in the skewed compound channel with inclined floodplains compared to the skewed compound channel with flat floodplains. Also, in skewed compound channels with inclined floodplains, the evolution of flow discharge along the skew part of the flume in each sub-section (including converging floodplain, main channel and diverging floodplain) is non-linear.

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