15d shows a steep slope which changes to mild it is

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Unformatted text preview: 2 curve and accelerates to critical flow near the overfall. The falling stream will be supercritical. The overfall “controls” the water depths upstream and can serve as an initial condition for computation of y(x). This is the type of flow which occurs in a weir or waterfall, Sec. 10.7. The examples in Fig. 10.15 show that changing conditions in open-channel flow can result in complex flow patterns. Many more examples of composite-flow profiles are given in Refs. 1, 3, and 18. 10.7 Flow Measurement and Control by Weirs A weir, of which the ordinary dam is an example, is a channel obstruction over which the flow must deflect. For simple geometries the channel discharge Q correlates with gravity and with the blockage height H to which the upstream flow is backed up above the weir elevation (see Fig. 10.16). Thus a weir is a simple but effective open-channel flowmeter. We used a weir as an example of dimensional analysis in Prob. 5.32. Figure 10.16 shows two common weirs, sharp-crested and bro...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.

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