Side weirs are hydraulic structures widely implemented in urban drainage systems, irrigation channels and flood protection works. They have been extensively studied in the technical literature for almost a century. The flow across a side weir is an important example of spatially varied flow, characterized by significant complexity factors. The analysis is generally performed by means of a momentum or energy approach. The momentum approach is usually more accurate but usually leads to a formulation that is difficult to apply to a practical design. The energy approach, instead, is not as accurate when the free surface over the side weir is significantly higher than the same weir crest. An alternative solution for the study of single side weir in a circular pipe, operating in supercritical flow, is provided by a new theoretical model herein shown. The model was inspired by an experimental analysis of the flow power variation along the side weir. Assuming a constant decrease of the flow power along the weir, a new differential equation representing the free surface has been obtained. Experimental tests showed that the suggested model is reliable in representing free surface. Moreover, it allows to estimate the lateral outflow with good accuracy. In order to further validate the proposed formulation, it was also compared with other models of recognized value, showing comparable performance.
A Flow Power Based Approach for Side Weirs
GRANATA, Francesco;DE MARINIS, Giovanni;GARGANO, Rudy
2013-01-01
Abstract
Side weirs are hydraulic structures widely implemented in urban drainage systems, irrigation channels and flood protection works. They have been extensively studied in the technical literature for almost a century. The flow across a side weir is an important example of spatially varied flow, characterized by significant complexity factors. The analysis is generally performed by means of a momentum or energy approach. The momentum approach is usually more accurate but usually leads to a formulation that is difficult to apply to a practical design. The energy approach, instead, is not as accurate when the free surface over the side weir is significantly higher than the same weir crest. An alternative solution for the study of single side weir in a circular pipe, operating in supercritical flow, is provided by a new theoretical model herein shown. The model was inspired by an experimental analysis of the flow power variation along the side weir. Assuming a constant decrease of the flow power along the weir, a new differential equation representing the free surface has been obtained. Experimental tests showed that the suggested model is reliable in representing free surface. Moreover, it allows to estimate the lateral outflow with good accuracy. In order to further validate the proposed formulation, it was also compared with other models of recognized value, showing comparable performance.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
