An orifice meter with orifice diameter 15 cm is inserted in a pipe of diameter 30 cm. The pressure difference measured by a mercury-oil differential manometer on the two sides of the orifice gives 50 cm of mercury. Find the rate of flow of oil of specific gravity 0.9 when coefficient of discharge of the meter is 0.64.
Area A_{o}=\frac{\pi }{4}\times (15)^{2}
= 176.714 cm²
Area A_{p}=\frac{\pi }{4}\times (30)^{2}
= 706.838 cm²
and h=(\frac{13.6}{0.9}-1 )\times 50=705.555 cm of oil
Using the discharge equation,
Q=C_{d}\frac{A_{1}A_{2} }{\sqrt{A^{2}_{1}-A^{2}_{2} } }\sqrt{2gh}
or Q=0.64\frac{176.714 \times 706.838}{\sqrt{(706.838^{2}) – (176.714^{2}) } }\sqrt{2×9.81×100×705.555}
or Q = 137414 cm³/s
or Q = 137.414 1/s