Unformatted text preview: a depression ( h 0): Subcritical approach flow will cause a water-level rise and supercritical flow a fall in depth.
Point 2 will be h to the right of point 1, and critical flow cannot occur.
Water flow in a wide channel approaches a 10-cm-high bump at 1.5 m/s and a depth of 1 m. Estimate (a) the water depth y2 over the bump and (b) the bump height which will cause the crest
flow to be critical. Solution
Part (a) First check the approach Froude number, assuming C0
(9.81 m/s2)(1.0 m) V1
gy1 Fr1 gy:
0.479 (subcritical) For subcritical approach flow, if h is not too large, we expect a depression in the water level
over the bump and a higher subcritical Froude number at the crest. With h 0.1 m, the specific-energy levels must be
2g E1 y1 (1.5)2
2(9.81) 1.0 1.115 E2 E1 h 1.015 m This physical situation is shown on a specific-energy plot in Fig. E10.6. With y1 in meters, Eq.
(10.39) takes on the numerical values
2 0.115 0 0.859 m, 0.451 m, and 0.296 m. The third (ne...
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- Spring '08
- Fluid Dynamics, Fig, e-Text Main Menu, subcritical flow