cylindrical shape with a smooth upstream and downstream transition (typ-
ically a sloping apron with a slope 1 : 2 to 1 : 2.25). For a height sof the crest
above the approach channel bed (e.g. 3.69 in Fig. 9.10) and the upstream
(approach) depth y 0 (6.00 in Fig. 9.10) computation using the potential
flow theory will result in a radius Rof the cylindrical sill which would not
influence (reduce) the discharge capacity of the structure (compared with
the case without the raised sill) for a given upstream water level. Typical
values for s/y 0 are 0.15 s/y 0 0.3 resulting in 2.5 R/s15. For further
details of the computation, particularly for the case of non-modular flow
see e.g. Dolez ̆al (1968).
368 DIVERSION WORKS
Fig. 9.3 Details of barrage and head regulator
