Unformatted text preview: ather sensitive to small effects, such as plate
thickness and sidewall boundarylayer growth. Small heads (H 75 mm) and small
slot widths (b 30 cm) are not recommended. See Refs. 19 and 20 for further details.
The V notch, in Table 10.2c, is intrinsically interesting in that its overfall has only one
length scale, H — there is no separate “width.” The discharge will thus be proportional to
3
H5/2, rather than a power of 2 . Application of Bernoulli’s equation to the triangular opening, in the spirit of Eq. (10.52), leads to the following ideal flow rate for a V notch:
V notch: Qideal 8 2
15 tan 2 g1/2H5/2 (10.59) where is the total included angle of the notch. The actual measured flow is about 40
percent less than this, due to contraction similar to a thinplate orifice. In terms of an
experimental discharge coefficient, the recommended formula is
QV notch Cd tan 2 g1/2H5/2 Cd 0.44 for 20° 100° (10.60) for heads H 50 mm. For smaller heads, both Reynoldsnumber and Webernumber
effects may be imp...
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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.
 Spring '08
 Sakar

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