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Titel |
An experimental analysis of dispersion and diffusion processes in compound channels |
VerfasserIn |
Sonia Angiolani, Giovanni Besio, Alessandro Stocchino, Maurizio Brocchini |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250072131
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Zusammenfassung |
The analysis of mixing processes in natural streams is very important to understand and
predict water contamination and nutrient dispersion. Pollutant behavior is usually modeled by
a standard advection-diffusion equation for the concentration. This equation allows an
adequate description of the evolution of the passive tracers once the diffusivity tensor has
been provided, estimation of which strongly depends on the local character of the flow
field.
An experimental campaign based on Particle Image Velocimetry (PIV) measurements of
free-surface velocities forms the basis for an analysis of mixing processes which occur in a
compound channel flow. The flow mixing is analyzed from a Lagrangian point of view, i.e. in
terms of single and multiple particle statistics (absolute and relative dispersion and
diffusivity) and of the related mean flow characteristics. In the present study the asymptotic
behavior of mixing characteristics for larger times, once the ballistic regime has
been attained, has been analyzed in terms of the absolute diffusivity in order to
characterize typical values of longitudinal and transversal dispersion coefficients.
Different series of experiments (related to the ratio rh between the main channel flow
depth and the floodplain depth, which classifies the flow in Shallow, Intermediate
and Deep, and Fr the Froude number) have been performed and the asymptotic
value of the absolute diffusivity has been evaluated. The present study highlights a
stronger dependence of coefficients on the main flow characteristics. The results are
compared with several dispersion analyses for both the longitudinal dispersion
coefficient and the transverse turbulent mixing coefficient presented in the literature. |
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