American Society of Civil Engineers

Compromise Orifice Geometry to Minimize Pressure Drop

by Ziji Zhang, (Div. of Hydr. Engrg., Royal Inst. of Tech., Osquars backe 33, 100 44 Stockholm, Sweden) and Junmei Cai, (Dept. of Hydr. Engrg., Tsinghua Univ., Beijing, 100084, China)

Journal of Hydraulic Engineering, Vol. 125, No. 11, November 1999, pp. 1150-1153, (doi:

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Document type: Journal Paper
Abstract: A compromise orifice geometry is experimentally proven to cause a smaller local pressure drop in conduit flow. An orifice installed as an energy dissipater 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.

ASCE Subject Headings:
Energy efficiency
Energy loss
Flow control