Quantcast Applications of Localized Mixing

 
  
 
d. The next task is the determination of the depth of penetration of the jet required to ensure
release of the pumped water. This depth will usually be the center-line elevation of the intake.
Computational methods for depth of penetration of a jet are given in Holland (1984).
e. The initial jet characteristics are to be determined next. Using computations of Albertson et
al. (1950) and Holland (1984), the initial jet diameter and velocity can be determined. The selection of
a pump to meet these criteria, which can be obtained from pump manufacturers, can then be made.
4.6.2.4 Applications of Localized Mixing
A number of applications of localized mixing have been made. Mechanical pumps used in these
applications range from large-diameter axial flow pumps to relatively small-diameter direct-drive
mixers. Limitations to the site specific application of surface water pumps include, temperature increase
in tailwater, availability of sufficient electric power at the intake, and problems with trash and debris in
the reservoir.
The earliest reported use of a pump to locally mix a reservoir for release improvement was
Garton and Rice (1976). This work was based on a large-diameter (16.5-ft) axial flow pump used in
lake destratification experiments on Lake Arbuckle in Oklahoma. The 16.5-ft-diam axial flow pump
generated up to 207,000 gal/min of discharge And was successful in improving the release DO by 1 to
2 mg/L.
In 1977, localized mixing tests were conducted at Lake Okatibbee in Mississippi. These tests
used a 1.83-m-diam axial flow pump designed to pump 1.7 m3/sec while the release structure released
1.4 M3/sec. Results of these tests indicated an improvement in release DO of 1.0 mg/L and warmed
the release by 3.6 oC (Dortch and Wilhelms 1978). Although the pumping rate was nearly 50 percent
of the discharge rate from the structure, additional improvement could have been possible with an
improved design. In addition, these researchers stated that the application of this technique at other
projects with higher discharges or deeper pools may not be as successful (Okatibbee Lake is
approximately 9 m deep).
In 1980, a series of localized mixing tests were conducted on Pine Creek Lake and Lake
Texoma in Oklahoma (Robinson 1981; Robinson, Garton, and Punnett 1982). These tests, using axial
flow pumps with diameters of 1.22, 1.83, and 2.44 m, were designed to investigate pump performance
with varying propeller diameter and reservoir release rates.
Conclusions from these tests indicated that improvement in release quality was feasible, but only
for water quality constituents that display an increase with depth (excluding DO and temperature), and
that increases in the pump propeller diameter increased the discharge ratio or dilution factor. However,
a reduction in water quality was observed when the pumping rate exceeded the release rate. This may
have been due to overpenetration of the pumped jet since the outlet level for these tests was at an
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