Compromise Orifice Geometry to Minimize Pressure Drop

Abstract

A compromise orifice geometry is experimentally proven to cause a smaller local pressure drop in conduit flow. An orifice installed as an energy dissipator in a flood conduit is required to dissipate a designed amount of energy at the design discharge. A small local pressure drop is preferred to minimize the cavitation risk. Experiments show that the orifice geometry strongly affects the wall-pressure distributions. Although sharp-edged and streamlined orifice plates can meet the energy dissipation requirement, they both cause larger pressure drops than do orifices shaped with compromise geometry that is neither sharp-edged nor streamlined. A compromise between the contraction ratio and the abruptness of transition helps minimize pressure drop. If the required energy loss increases, the compromise geometry should be more streamlined and have a smaller contraction ratio. The present paper provides the possibility of using alternative orifice geometry, such as a sloping-approach orifice, to reduce the risk of cavitation.