Numerical Simulation of Flow in Prismatic Compound Channels with Sloping Floodplains

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Numerical Simulation of Flow in Prismatic Compound Channels with Sloping Floodplains

ارائه دهنده: Provider: Zahra Kazemi

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

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: جناب آقای دکتر جلال صادقیان - جناب آقای دکتر مرتضی شکری

زمان و تاریخ ارائه: Time and date of presentation: 2021

مکان ارائه: Place of presentation:

چکیده: Abstract: The hydraulic behavior in compound channels is more complex than simple channels due to the interaction between the main channel and the floofplains, and in order to design them, it is necessary to know some factors affecting their hydraulic behavior. To obtain this knowledge, the results of laboratory flumes with the results of numerical models can be used. The use of either of these two methods requires considerable expense and time. Another method that can be used is to combine laboratory results and existing application software that will minimize time, space and cost constraints if appropriate results are obtained. In this research, an attempt has been made to simulate the shear stress at the bottom of the main channel and floodplains and the average depth velocity distribution in a prismatic compound channel with sloping floodplains using Ansys Fluent software with standard k-ε turbulence model and compare with laboratory results. The compound channels modeled in this study include the main channel with a length of 17 meters, width of 400 and depth of 50 mm and floodplains with a width of 400 and 200 mm with a slope of 0.075 to the axis of the channel. The results of the present study showed that the slope at the bottom of the floodplains in the direction of the channel width causes gravitational force in these areas, which causes the flow in the direction of the channel width on the floodplains. In the areas of flow interaction, at greater relative depths, due to the interaction mechanism, the flow is more similar to the flow established in the compound channel without transverse slope of the floodplain. Due to the slope of the floodplains, at relative depths and lower discharges, due to the supercritical flow regime in some areas, successive hydraulic jumps are created on the floodplains, which causes the velocity distribution step and consequently the shear stress in these areas. Comparison of laboratory average depth velocities with numerical results showed that in the channel with 200 mm floodplain width, the velocity error measured in the main channel is 9.14% and in floodplsins is 8.42%. These values were 1.94% and 6.83% for channels with 400 mm wide floodplains, respectively. Key Words: compund channel, sloping floodplain, Ansys Fluent, shear stress, k-ε.

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