h 1 (m) Cv Q (m^3 s^1 )
0.10 1.003 0.62
0.20 1.009 1.78
0.30 1.018 3.30
0.38 ←by iteration ← 4.60
NON-MODULAR FLOW RATING CURVE
The following procedure is used. Assume the non-modular flow, Q, to be,
say, 6 m^3 s^1. Then H 2 0.375 m (Fig. 8.25). Estimating H 1 at 0.450 m,
H 2 /H 1 0.833. The drowned flow (non-modular) correction factor, f, can
be obtained from the plot in Fig. 8.26 (Water Resources Board, 1970)
betweenfandH 2 /H 1. Thus f0.965, and hence
QfQmodular
0.9655.95 (QmodularCdg1/2bH 1 3/2)
5.74 m^3 s^1 6.0 m^3 s^1.Repeating with different estimates of H 1 givesQ6m^3 s^1 for a
value of H 1 0.46 m. The iterative solution of the energy equation (equa-
tion (iv)) gives h 1 0.44 m. The following table lists the data for the non-
modular flow rating curve:
Q ( m^3 s^1 )h 1 (m)
6.0 0.44
8.0 0.55
10.0 0.64
12.0 0.72
14.0 0.80
17.0 0.91
WORKED EXAMPLES 359
Fig. 8.26 Correction factor ffor non-modular flows