Author(s): Rawya M. Kansoh
Linked Author(s):
Keywords: Flow; Weirs; Orifices; Control structures
Abstract: Weirs and Orifices are used as control structures for variable discharges in different open channel cross sections. Numerical and experimental models have been used and evaluated for different types of sharp edged orifices. In the theoretical approach, discharge equations have been obtained including factors such as head of water acting on the center of gravity of the orifice along with its geometry. Sharp edged orifices used in this research had the shapes of a square, rectangular, triangular, circular and elliptical. Theoretical investigation included the variation of the discharge coefficient with various factors and dimensional analysis. Experimental set-up has been prepared to investigate the flow characteristics through the same different shapes of orifices considered in the theoretical work. The aim of this research is to obtain the discharge characteristics (discharge equations and discharge coefficient) for all shapes. The limits between large and small orifices have been determined; similarly the geometric dimensions ratios of orifice shapes and discharge characteristics. Best sharp edged orifice has been determined which gives maximum discharge coefficient with minimum head loss. Weirs or notches are normally classified as rectangular, triangular or V-notch, trapezoidal and parabolic weirs. Evaluation has been made to find groups of outlets (weirs) in which Q varied as the head raised to an integer i. e. H 1. 00, H 2. 00, H 3. 00, H 4. 00. Charts and equations have been derived for different shapes of weirs. Experimental and numerical models have been performed and relationships between the discharge and the head have been determined for groups of outlets which have the discharge varying such as QαH 1. 00, QαH 2. 00, QαH 3. 00, QαH 4. 00.
Year: 1999