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

Version 1.0, June 2005
USER'S MANUAL FOR CORHYD:
AN INTERNAL DIFFUSER HYDRAULICS MODEL
by
Tobias Bleninger, Gerhard H. Jirka
Institute for Hydromechanics, University Karlsruhe
Kaiserstr. 12, 76128 Karlsruhe, Germany, bleninger@ifh.uka.de
http://www.cormix.de/corhyd.htm
Abstract
Submerged multiport diffusers for waste water outfalls are designed often, considering steady
flow conditions for far future scenarios. Design aims for lower costs for material use and
pumping energy and the minimization of environmental impacts. Inadequate attention on the
internal diffuser hydraulics also for off design conditions thereby often result in hydraulic
problems like partial blockage, high head losses, uneven flow distribution, salt water intrusion
and poor dilution causing higher energy demands and stronger environmental impacts.
The CorHyd computer program has been developed for the calculation of velocities,
pressures, head losses and flow rates inside the diffuser pipe and, especially, at the diffuser
port orifices to analyze and optimize diffuser design alternatives as well as existing diffuser
configurations for different and varying discharge and ambient conditions. The calculation is
based on the application of the steady continuity and work-energy equations between ambient
fluid at the discharge points and the effluent inside the diffuser pipe. Emphasis was given to
the implementation of all occurring losses especially if high risers, duckbill valves, multiple
ports and more complex discharge configurations are applied.
Detailed calculations for the internal manifold hydraulics in the outfall pipes show a strong
sensitivity on the representation and formulation of local losses even for relatively simple
riser/port configurations. An optimization methodology yields a homogeneous discharge
distribution along the diffuser, minimization of the total head and prevention of sedimentation
or ambient water intrusion in the diffuser under varying inflow and ambient conditions. The
final design achieves lower costs for material use and operation as well as the minimization of
environmental impacts and operational stability for off-design conditions.
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