In water quality management and environmental protection of lakes or
reservoirs, techniques such as artificial destratification and aeration for water
quality improvement and fishkill prevention are used with increasing
frequency. The disposal of waste water and heat are major problems in
environmental engineering. In both cases the interaction of jet flows and
weakly density..-stratified ambients including the mixing is currently not well
understood and difficult to predict. In this study 1-D and 2-D numerical
simulation models and laboratory measurements are employed to provide
information on jet flows and mixing in density-stratified waters. Flow and
thermal fields and their evolution are simulated. Jet trajectories are
predicted and analyzed especially in low temperature water where strong
nonlinearity between water density and temperature exists. Mixing processes
which result in destratification and dilution are simulated and analyzed.
Laboratory experiments are designed and conducted to observe and
measure the basic features of buoyant water jet flows and mixing in a
stratified basin. Experiments are conducted with different initial conditions
and governing parameters. Data of temperature profiles are analyzed and
used to verify the I-D jet-mixing model.
The one-dimensional numerical simulation model is developed to describe
the gross behavior of jet flows and mixing. The integral I-D model is
incorporated into an existing multi-purpose dynamic lake water quality model
(MINLAKE) for practical application. This incorporation makes it possible to
evaluate effects of jet flows on mixing and water quality of aquatic
environments. The temperature submodel in MINLAKE is also extended to
winter conditions so that a warm water discharge into an ice-covered lake
can be investigated. The model developed for winter predicts the growth and
decay of ice and snow covers. and thermal structures of a lake in a cold
climate. Based on numerical analysis and experimental data, information on
design and operation of artificial mixing (destratification) devices is also
Details of flow fields, which would be too complicated to measure in the
laboratory and are omitted in the 1-D simulation model, are stp.died in a
two-dimensional numerical simulation model. The Reynolds equations are
solved with a buoyancy-extended k-E turbulence model asa closure. The
flow and thermal fields are modeled as an unsteady phenomenon. The 2-D
model is verified against existing data for a vertical jet impinging on a plate
and data for offset jets. This 2-D model is applied to simulate the details of
flow and mixing of a warm water discharges into a cold lake with ice cover.
Buoyancy reversal results in dramatic changes in jet flow behavior.
Gu, Ruochuan; Stefan, Heinz G..
Mixing of Temperature-Stratified Lakes, Reservoirs or Ponds by Submerged Jets.
St. Anthony Falls Hydraulic Laboratory.
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