method for designing a localized mixing system was discussed, along with references for computational
procedures. Applications of localized mixing have been tested in a number of locations with axial flow
and direct-drive mixers and large systems have been permanently installed at 2 TVA dams since 1994.
Several numerical techniques have been formulated which may assist in the design of a localized mixing
system. Summary information on this technique is given in Table 4.6.3.
Table 4.6.3
Summary of Localized Mixing
Characteristic
Description
Targets
Improved water quality by mixing or diluting hypolimnetic waters with
epilimnetic waters.
Mode of action
Surface pumps are used to force surface waters down into the hypolimnion
and the withdrawal zone.
Effectiveness
Effective for stable stratification.
Longevity
Seasonal.
Negative features
Possible overpenetration of the jet may strike the bottom and cause
resuspension of sediment and erosion.
Temperature increase in releases associated with using warm surface water
for DO improvement may be undesirable, especially for cold water fisheries
in tailwater.
Partial destratification of an area is possible.
Significant maintenance is required for electromechanical equipment, flexible
connections and debris control.
Costs
Moderate.
Applicability to
Very applicable to reservoirs without selective withdrawal structures to
reservoirs
increase the withdrawal of surface waters.
4.6.3 REFERENCES
Albertson, M. L., Dai, Y. B., Jensen, R. A., and Rouse, H. 1950. "Diffusion of Submerged Jets,"
Transactions of American Society of Civil Engineers, Vol 115, pp 639-697.
4.6-11
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