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EXAMPLE OF COURSEWORK. Siphon Spillway Design. EXAMPLE: Full resevoir level (m ) = 200 Level of the centre of the outlet (m ) = 195 High flood discharge (m 3 /s ) = 580 m3/s Bed level of the river (m ) = 180 Base width of the body wall (m ) = 7 High flood level (m ) = 210
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Siphon Spillway Design EXAMPLE: • Full resevoir level (m) = 200 • Level of the centre of the outlet (m) = 195 • High flood discharge (m3/s) = 580 m3/s • Bed level of the river (m) = 180 • Base width of the body wall (m) = 7 • High flood level (m) = 210 • Cd (siphon discharge freely) = 0.6
Solution: • From the information above, we can determine the number of siphon units required to pass the flood safely. • Calculate maximum operative head, H • H = High flood level – Level of centre of siphon outlet • = 210 – 195 • = 15 m • 2. Calculate full pipe discharge, • q=Cd x A x [(2gH)^0.5] • *Cd, siphon coefficient is given 0.6 • *Assuming the dimension of throat, width 4m x height 2m • *H is the maximum operative head.
q=Cdx A x [(2gH)^0.5] q=0.6 x 8 x [(2x9.81x15)^0.5] = 82.3 m3/s Number of units required, No. of units = High flood discharge / full pipe discharge = 580 / 82.3 = 7 units
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