Outfall Dilution: The Role of a Far‐Field Model
Publication: Journal of Environmental Engineering
Volume 111, Issue 4
Abstract
Effluent dilutions predicted by near‐field models do not realistically reflect near‐field conditions in tidally influenced coastal waters since they neglect the advection of the pollutant cloud over the source. A theoretical solution has been developed for the case in which a conservative pollutant is released from a line source into a uniform unsteady flowing ambient where diffusion is only significant in the cross‐stream direction. Considering the case of a sinusoidal variation of velocity along the streamwise principal axis, it has been shown that the expected concentration at a source located in a typical flow field may increase by as much as 15% per cycle over that predicted by the near‐field model. A hypothetical outfall was analyzed using real data and a dispersion model which accounts for the near‐, as well as far‐field mixing. The near‐field model was found to underestimate the average dilution at the source by about 21%. Extreme values were also underestimated. The results of this study indicate that a complete dispersion model should be used in predicting dilutions in outfall mixing zones of coastal regions.
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References
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 111 • Issue 4 • August 1985
Pages: 473 - 486
Copyright
Copyright © 1985 ASCE.
History
Published online: Aug 1, 1985
Published in print: Aug 1985
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