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|Parametric investigation of localized mixing in reservoirs
|Hydraulics Laboratory (U.S.)
Environmental and Water Quality Operational Studies (U.S.)
Holland, Jeffery P.
|Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Abstract: During the late spring or early summer months, many Corps of Engineers reservoirs become thermally stratified. The subsequent density stratification limits or negates vertical mixing in these reservoirs with the result that vertical strata of decreasing water quality are formed. Releases from the lowest of these strata, the hypolimnion, may be of generally poor quality due to its relative oxygen deficiency which results from the coupling of limited vertical mixing and hypolimnetic oxygen demand. Localized mixing, a simple and relatively inexpensive method for the enhancement of these releases, utilizes the effects of jet mixing to transport high-quality epilimnetic water down to the hypolimnetic withdrawal zone for dilution of the release. In order to effectively enhance downstream release quality, the localized mixing system must produce a jet of sufficient quantity and initial momentum so that it will both penetrate into the hypolimnion and adequately dilute the release. The results of laboratory investigations showed jet penetration into the hypolimnion to be a linear function of the densimetric Froude number at the thermocline. Qualitative analysis of the dilution of a given release showed a maximum dilution expected beyond which the additional pumping of epilimnetic water resulted in wasted resources. From these results, a procedure for the initial design of a localized mixing system was synthesized. An example of this design procedure is presented.
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