Mathematical models to predict water temperature distributions
resulting from heated water surface discharges usually consider three
subregions of the flow field: (a) an outlet region or zone of flow
establishment (ZFE), (b) a zone of fully established jet flow, and (c)
a far field with mostly passive dispersion. Of these three regions,
zone (b) can be treated mathematically most readily using integral
techniques; zone (c) requires input specifying mean flow and turbulence
of the ambient flow field; and zone (a) depends essentially on the
geometry of the outlet and the discharge characteristics in terms of
the velocity and temperature of the water.
The results of an experimental study dealing with zone (a) are
reported. The discharge channel had a rectangular cross section and led
into a deep, wide reservoir. The aspect ratio (width-to-depth ratio) of
the channel, the volumetric discharge rate, and the discharge temperature
were varied. A cross-flow was imposed in some of the experiments.
The length of the zone of flow establishment, Xo or So, was
measured in terms of mean excess temperature, mean velocity, and turbulence
intensity along the trajectory. The length, Xo or So, was
related to channel aspect ratio A,
outlet densimetric Froude number
Fo, and cross-flow-to-jet velocity ratio R. Total volumetric flow
rates during flow establishment were established as a function of distance
along the jet axis and related to A and Fo. The results are
useful either for extension of existing mathematical models of fully
developed heated water surface jets or for verification of mathematical
models of the zone of flow establishment.
Office of Research and Monitoring U.S. Environmental Protection Agency
Stefan, Heinz; Bergstedt, Loren; Mrosla, Edward.
Flow Establishment and Initial Entrainment of Heated Water Surface Jets.
St. Anthony Falls Hydraulic Laboratory.
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