user's manual for corhyd: an internal diffuser hydraulics model - IfH

concrete pipe with a diameter of 2.4 m including a 449 m long diffuser section with 90 ports
on each side of the pipe, each with a nominal diameter of 0.17 m, a spacing of 5 m and
pointing downwards with an angle of 45° to the horizontal (Carvalho et al., 2002, Fig. 24 and
Fig. 25). The diffuser is in a depth of about 27 m. The slope of the diffuser line could not be
found in literature. The Ipanema outfall is one of the few outfalls which have been monitored
in detail, with special emphasize on mixing characteristics (Carvalho et al., 2002). These
monitoring studies showed in general good mixing characteristics. At commissioning 59 of
the 180 ports have been closed on purpose to achieve reasonable flow conditions until design
flow is reached. Since 1996 all ports are discharging. The constructional design itself is
unusual, with a concrete diffuser line fixed on piles above the seabed. The piles proofed to be
the weak point of the construction, where pile breaks lead to a major rupture in year 2000.
Today simpler and cheaper laying methods are available (e.g. HDPE pipes with weights or
laid in a trench), which promise to be more resistant to dynamic wave forcing and currents.
Fig. 23: Locoation map of the Ipanema outfall of the city Rio de Janeiro in Brazil (Carvalho, 2003).
Institut für Hydromechanik, Universität Karlsruhe 53