Critical submergence for a frontal intake in a dead-end canal flow

CRITICAL SUBMERGENCE FOR A FRONTAL INTAKE IN A DEAD-END CANAL FLOW (M. Sc. Thesis) Salih Cem GÜLCAN GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY January 1999 ABSTRACT When the vertical distance of the intake to the free surface ("submergence" of the intake) is not sufficient, the air enters the intake by means of an air-core vortex and considerably decreases the efficiency of the intake and affiliated structures. The value of the submergence of the intake when the air-core vortex just starts entraining air to the intake is known as the "critical submergence" for the intake. There are several studies about the free surface air-core vortex and the critical submergence. In these studies an intake o. circular cross-section is considered and it is believed that the occurrence of the air-core vortex is same for all types of flow conditions and geometry. However; in hydraulic structures (such as dams etc.) the cross-section of the intake is mostly rectangular and the intake takes place at the upstream face of the structure (the dead-end). In this study, the critical submergence for the intakes of both the circular and the rectangular cross-sections (not considered in the previous studies) are studied experimentally arid theoretically. It is found that the critical submergence of the intake at the dead-end highly depends on the flow conditions and geometry. Experimental and theoretical (potential solution) results are compared and the agreement is found to be satisfactory. Science Code Key Words Page Number Adviser 624.02.01 Dead-end, critical submergence, canal flow, air-core vortex 90 Assoc. Prof. Dr. Nevzat YILDIRIM