THE FRICTION RESISTANCE EFFECT ON THE HYDRAULIC JUMP LOCATION AND ENERGY DISSIPATION, A LABORATORY STUDY

Sadiq Jafar, Muthanna

	THE FRICTION RESISTANCE EFFECT ON THE HYDRAULIC JUMP LOCATION AND ENERGY DISSIPATION, A LABORATORY STUDY
KUFA JOURNAL OF ENGINEERING
Article 1, Volume 7, Issue 2, 2016, Pages 90-103
Author
Muthanna Sadiq Jafar
Abstract
The location of the jump downstream the hydraulic structures outlets is an important parameter taken into considerations within the construction of the downstream protection works. One of the ways of moving the jump into a closer distance from the outlets is to raise the tail water level. In this research, a flow partitioning structure, FPS, designed, carried out, and installed downstream a sluice gate to apportion the cross sectional area of the flow and, then, increase the resistance of the friction force by increasing the walls of flow. The FPS shaped as a sectioned triangular prism consists of sets of 2.6cm×2.6cm iron square-section pipes formed with direction of the flow. The FPS with a vertical front face consisting of 16×11, rows × columns, of pipes extended 10cm downstream and held by a 0.5cm, thickness, iron bars and welded together to prevent any egression of the pipes from the FPS. This combination of the pipes and bars made a width of 29.6cm and height of 42.6cm to fit, approximately, the flume cross sectional area dimensions. The downstream face made with an inclination of 45o to prevent the free fall of the water. The system (which consists of a sluice gate, FPS, and rising weir) installed in a horizontal flume of 0.3m width, 0.45m depth, and 15m length. The system operated with flow rates ranged from 11.11 to 36.24l/s with different gate openings in 27 tests. In each test, the hydraulic jump formed downstream the sluice gate and the FPS once placed downstream the jump and once removed, in the same test, with maintaining the same flow conditions, and measurements are taken to investigate the effect of the FPS on the jump. The results show that the additional friction resistance by the FPS increased the tail water level and forced the hydraulic jump towards the sluice gate, in which the FPS produced a converging distance ranged from 0.64m to 5.34m. This convergence of the jump lowered the head losses of the flow before the jump and then increased Froude Number, Fr, and produced higher y2/y1 value. The increased value of y2/y1 increased the energy dissipation of the jump, in which the jump produced energy dissipation ranged from 8.47 to 85.38% with the existence of the FPS instead of 5.91 to 66.14% without it, with same flow conditions. In spite of the considerable increase in the tail water level downstream the FPS, there was no significant differences of the dissipated energy with and without the FPS for the whole system, in which the energy dissipation ranged from 14.05 to 55.91% with the FPS and ranged from 13.57 to 55.09% without it.
Keywords
Hydraulic jump; Flow partitioning structure; Converging distance; Energy dissipation

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