Discussion of 'Discharge Coefficients for Orifices Cut into Round Pipes' by Alex J. McLemore, John S. Tyner, Daniel C. Yoder, and John R. Buchanan

摘要

The authors are gratefully acknowledged for presenting an opportunity to examine (McLemore et al. 2011) their method for measuring and describing the discharge coefficient (C_d) for flow into an orifice cut into a round pipe. The paper under discussion (McLemore et al. 2011) mainly deals with the prediction of the effect of riser pipe curvature on an orifice area. In line with this concept, four different descriptions of an orifice cross-section area (A) were given and examined, while at the same time an attempt was made to fit C_d to measured discharge experiments. The following conclusions were drawn in the present examination (McLemore et al. 2011): (1) C_d decreases as the orifice diameter approaches the diameter of the riser; (2) C_d increases with an increasing d/D (ratio of bit diameter to riser diameter); and (3) as h (head at center of orifice) decreases, the vena-contracta area (A_(vc)) increases, which is what causes C_d to increase at low h/d values and is why the error associated with an assumed h is not evident in the measured discharge data.