Experimental Study of Discharge Coefficient in Piano Key and Labyrinth Side Weirs with Constant Cycles

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of Discharge Coefficient in Piano Key and Labyrinth Side Weirs with Constant Cycles

ارائه دهنده: Provider: Saeid Jeddi

اساتید راهنما: Supervisors: Dr Bahram Rezaei- Dr Jalal Sadeghian

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr Majid Fazli - Dr Morteza Shokri

زمان و تاریخ ارائه: Time and date of presentation: 2020-09-20

مکان ارائه: Place of presentation: آمفی تئاتر دانشکده مهندسی

چکیده: Abstract: Weirs or Spillways are one of the oldest and most important hydraulic structures and have several applications such as the passage of excess water due to floods, controlling the water level in the reservoir, flow diversion, reducing river erosion, and calculating the flow rate. An example of a type of weirs is the side weir. The purpose of using side weir in water transmission and distribution systems is to control the flow level, water deflection, and prevent damage caused by floods. Among the various forms of side weirs, we can mention nonlinear weirs in the crown. Nonlinear weirs come in a variety of shapes, such as Labyrinth weir and piano key weir, and are used where there is a length limit for constructing the weir to increase the length of the crown and thus increase the discharge capacity. In Labyrinth and piano key weir, the discharge coefficient is of particular importance and in this research, the discharge coefficient of these weirs has investigated as a side weir. Laboratory models of triangular, trapezoidal and rectangular Labyrinth weirs and piano key weirs in this study were each made in 3 cycles and 4 heights of 5, 10, 15 and 20 cm using 5 mm Plexiglas sheets with an opening length of 57 cm and the piano key weirs were type A. The experiments performed in this research were carried out in the research channel of the hydraulic laboratory of Bu-Ali Sina University with a length of 10 meters and a width and height of 60 centimeters. Also, the current flowing on the side weirs is of the type of locative variable with decreasing discharge, and the De-Marchi equation has been used to investigate the discharge coefficient of the weirs. In triangular Labyrinth weirs, the discharge coefficient of weir with a height of 5 cm has increased on average compared to weirs with a height of 10, 15, and 20 cm, respectively, 17.9, 22.3, and 26.8%. In trapezoidal Labyrinth weirs, the discharge coefficient of weirs with a height of 5 cm has increased on average compared to weirs with a height of 10, 15, and 20 cm, respectively, by 11.4, 14, and 17.6%. In rectangular Labyrinth weirs, the weirs discharge coefficient with a height of 20 cm has increased on average compared to weirs with a height of 5, 10 and 15 cm by 34, 7.3, and 14.1 %, respectively. In piano key weirs, the weirs discharge coefficient with a height of 15 cm has increased by an average of 9.3, 5.5, and 9.2% compared to weirs with a height of 5, 10, and 20 cm, respectively. In all side of the Labyrinth and piano key side weirs, the discharge coefficient (Cd) and the flow rate passing from the side weir to the linear weir (QL /Qn)have been decreasing relative to the height of the water blade on the weir to the height of the weir (Ht/P), and as the value of Ht/P increases, the values of Cd and QL /Qn decrease, this decreasing process is greater for smaller weirs, and decreases with increasing the weir height, which ultimately results in a change in the performance of the Labyrinth weir and piano key weir to the linear weir performance. At a certain Ht/P ratio, weirs with lower heights have the highest discharge coefficient and vice versa for weirs with higher heights. In the comparison of rectangular Labyrinth weir and piano key weir laterally and directly, when weirs in the channel are used perpendicular to the flow axis, directly, piano key weirs are more efficient than Labyrinth weirs. However, in the present study, when the mentioned weirs were tested laterally in the channel, the result was the opposite, and the rectangular Labyrinth weirs had better efficiency and performance than the piano key weirs.

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