EVALUATION OF THE HYDRAULIC PERFORMANCE OF COMPOUND SHARP- CRESTED OVER FALL WEIRS

Abstract

Abstract The hydraulic relationships of flow through the weir of different common shapes were investigated in this study. The hydraulic performances of weirs were carried out experimentally, by using eight different types of weir models, and the effect of various shapes of the weir to specify different hydraulic parameters such as coefficient of discharge Cd, weir constants K & n values, energy dissipation ratio E % for selecting best flow measuring weir type. The experimental work was carried out on a tilted rectangular flume with 7.5 m long, 0.30 m wide and 0.45 m deep with discharge range 0.50 – 20.95 l/s. The experimental results of this study showed that the dissipation energy corresponding to triangular notches is larger than resulted from rectangular notches. For compound notches of rectangle and triangle, turbulence in flow increases as the angle of lower notch decreases. Thus, this type with an angle of ( θ =120 ο ) is the most efficient between the studied models, which gives the average coefficient of discharge (Cd) 0 .82, the value of ‘K ‘is equal to 0.75 and’ n’ values of 1.96, and the dissipation of flow energy ratio of (35.86%) for steady type jump. Finally, depending on a statistical basis, this study derived empirical relationships to estimate the coefficient of discharge with acceptable values of coefficient of determination