FLOW-3D MODEL: AIR VALVE TOOL AND APPLICATION TO CONTROL THE OUTFLOW DISCHARGE OF SIPHON SPILLWAYS

Abstract

This paper introduces the air valve tool in the Flow-3D model and application to control the outflow discharge of siphon spillways in reservoirs. The air valve in the Flow-3D model is the orifice in which the airflow can pass through by setting up the external pressure as the atmospheric pressure. The air valve tool is located in the air vent at the siphon crest where the negative pressure occurs. When the air valve opens, the atmospheric pressure will contribute to the negative pressure at the siphon crest, then the pressure is increased and the velocity is decreased in the siphon. Therefore, the outflow discharge of siphon spillways may be reduced when the air valve opens. Contrarily, the outflow discharge may be increased when the air valve closes. This technique is simple but efficient in the purpose of controlling the outflow discharge of siphon spillways. Finally, the flood disaster may be avoided by this efficient controlling technique.