Experimental Study of the Effect of Shape and Dimensions of Abutments on the Flow Pattern in Compound Channel with Sloping Floodplains

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of the Effect of Shape and Dimensions of Abutments on the Flow Pattern in Compound Channel with Sloping Floodplains

ارائه دهنده: Provider: Roghayeh Jalili Noori

اساتید راهنما: Supervisors: Dr Majid Fazli

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr Bahram Rezaei and Dr Morteza Shokri

زمان و تاریخ ارائه: Time and date of presentation: 2023

مکان ارائه: Place of presentation: Seminar Hall 2

چکیده: Abstract: Bridges are among the most of important and productive river structures and are considered as the key of communications ways, therefore, the principled and precise design of this structure is of great importance. One of the main causes of the failure of many bridges before the end of their life is the lack of attention to hydraulic standards in their design, implementation and maintenance. The presence of the base and side abutments of the bridge across the river reduces the width of the flow and the deviation of the flow lines. The flow pattern in rivers and around bridge abutments is very complex. In general, calculation and construction of bridge foundations and abutments are one of the most important and sensitive stages of a bridge construction project. One of the most important things that can be mentioned in this regard is the information related to the speed distribution and flow pattern around the base and abutments. Due to the fact that so far there has been little research on the effect of the abutment on the flow pattern around it, especially in the compound channels and especially the compound channel with the sloping floodplain and it comparison with other dimensions of the abutments, it seems that this research can be used in this field. Be fruitful in the present research, the flow pattern around the bridge supports in the compound channel with steep floodplains has been investigated in a laboratory manner. The experiments were carried out at a relative depth of 0.5 and a flow rate of 200 m3/h or 55.56 lit/s. measurements were made in the presence of four abutments with widths of 5, 10, 15 and 20 cm and same length of 13 cm, from a distance of 0.5m upstream of each abutment to about 0.9m downstream and at different longitudinal, transverse and depth distance. Using the results obtained, the flow pattern and velocity in the direction of the flow in the horizontal plane, transverse diagrams and longitudinal diagrams, the transverse distribution of the average velocity in depth, the length and width of eddies, vorticity around the longitudinal axis and the vertical axis, the lowering of the water level in different longitudinal levels. And the depth changes of longitudinal, transverse and height velocity components have been investigated. According to the results, the flow lines near the abutment are closer to each other and deviate towards the middle of channel. Also, due to the placement of the abutments in the flow path, a flow vortex is formed upstream and downstream of the abutment, which in general can be said to increase the length and width of the upstream and downstream vortex as the width of the abutment increases. In the presence of abutment number 4, a vortex is also formed in the wall of the main channel. The amount of vorticity around the longitudinal and vertical axis is the highest in the upstream and in front of the abutment and near the wall, and it decreases until near the junction point of the floodplain and the main channel and then increases. In the downstream, the maximum amount of vorticity occurs after crossing a width equal to the width of the abutment and this value gradually decreases as it moves from the channel wall to the middle of the main channel. If the width of the abutment increases to more than 50% of the width of the flood plain, there is no flow entering the flood plain downstream of the abutment and all the flow passes through the main channel. The depth changes of the velocity components increased with the increase of the width of the abutment, the largest amount of longitudinal, transverse and depth components of the speed is observed in front of the abutment and the greatest change of direction in the components is observed in the downstream sections of the abutments.