Comparison and Study of Discharge Coefficient of Trapezoidal Labyrinth Spillways with Regular and Irregular Lengths in the Plan

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Comparison and Study of Discharge Coefficient of Trapezoidal Labyrinth Spillways with Regular and Irregular Lengths in the Plan

ارائه دهنده: Provider: ali yari

اساتید راهنما: Supervisors: Dr. Jalal sadeghian

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. bahram rezaei & Dr. mortaza shokri

زمان و تاریخ ارائه: Time and date of presentation: 15/03/2022 16:00

مکان ارائه: Place of presentation: Place of presentation

چکیده: Abstract: The most important hydraulic structures used in the dam industry are overflows, which are constructed as a safety facility for depletion of untimely flood currents. These structures must be stable and have the necessary potential and ability to safely pass untimely currents and floods and be economically justifiable. Technically and economically, in order to increase the discharge capacity within the specified width of the spillways, the labyrinth spillway is used. The important parameters affecting the amount of discharge capacity is the relative height of the upstream water, the shape and length of the spillway. Among them, the most important effective parameter is the length of the spillway. In fact, in order to increase the effective length of the spillways, labyrinth spillway have been designed by deforming their shape in the plan, which will increase their efficiency and increase their discharge capacity. In such spillways, we face a decrease in efficiency and discharge capacity due to the interference of water flow blades during overflow. so in this study, which done in the hydraulic laboratory of Bu Ali Sina University with the aims to reduce the interference of water blades and increase the efficiency and discharge capacity of spillway, two different geometries are considered in the design of trapezoidal labyrinth spillway with different congress lengths in 5 cycles but with same effective length and height. The design of the five models of the first case (F) is such that the closer we get to the center of the spillway, the longer the middle congresses become, and the initial and final congresses have the shortest lengths. And the five models of the second mode (D) are designed in such a way that the closer we get to the center of the spillway the length of the middle congresses is shorter and the initial and final congresses have the longest length. In addition, in this study, a linear spillway model (A) and a trapezoidal labyrinth spillway model with regular congress length (B) have been constructed and tested and compared for further analysis. The results of performed experiments indicate that in labyrinth spillways of model F with irregular congress lengths, the highest discharge coefficient (C) occurs when has the lowest ratio. in these conditions with Increasing the volume of water passing from the canal to the flow rate No. 3 is the trend of changes (C), in contrast to the ratio is decreasing, and from this point on to the flow rate No. 6 in all F and D models, due to the interference of water flow blades and Due to the submergence of labyrinth spillway, the changes in the spillway discharge coefficient are not significant in relation to the increase in ratio , and in practice it can be said that the discharge coefficient at high discharges remains almost constant and unchanged. It is worth mentioning that in type D labyrinth spillway with irregular congress lengths, up to flow number 3, the trend of (C) changes is in contrast to the ratio is increasing. In different type F models with 75.7% of the impact length of water blades, efficiency and discharge coefficient of trapezoidal labyrinth spillways with irregular congress lengths is better than different type D models with 79% of the impact length of water blades, and their discharge coefficient compared to labyrinth spillways with the regular congresses length, has increased by a maximum 34.7% for type F and up to maximum of 23.4% for the type D

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