Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2024-12-19T06:17:35.555Z Has data issue: false hasContentIssue false
  • English
  • Français

The importance of discharge siting upon contaminant dispersion in narrow rivers and estuaries

Published online by Cambridge University Press:  20 April 2006

Ronald Smith
Ronald Smith
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW
Get access Rights & Permissions [Opens in a new window]

Abstract

Far downstream of a sudden contaminant release in a narrow channel the concentration depends on the cloud size. This is largely determined by the longitudinal shear dispersion and the time of travel of the cloud. Near the source the efficiency of the shear dispersion and the velocity of the cloud are strongly dependent upon the source location across the flow. The shear dispersion is greatest when there is both strong shear and strong turbulent mixing (i.e. away from either the centre-line or the banks), while the velocity is least and the time-lag maximized for a source on the banks. The quantitative influence far downstream can be characterized in terms of a deficit variance and a centroid displacement. In this paper exact results are derived for these quantities. It is shown that, except when the banks are extremely steep, the time-lag has the strongest effect and the concentration far downstream of a point discharge is minimized when the discharge is sited at the bank.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 108 , July 1981 , pp. 43 - 53
Copyright
© 1981 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aris, R. 1956 On the dispersion of a solute in a fluid flowing through a tube. Proc. Roy. Soc. A 235, 67–77.Google Scholar
Chatwin, P. C. 1970 The approach to normality of the concentration distribution of a solute in a solvent flowing along a straight pipe. J. Fluid Mech. 43, 321–352.Google Scholar
Chatwin, P. C. 1976 The initial dispersion of contaminant in Poiseuille flow and the smoothing of the snout. J. Fluid Mech. 77, 593–602.Google Scholar
Elder, J. W. 1959 The dispersion of marked fluid in turbulent shear flow. J. Fluid Mech. 5, 544–560.Google Scholar
Fischer, H. B. 1967 The mechanics of dispersion in natural streams. Proc. A.S.C.E., J. Hydraul. Div. 93, 187–216.Google Scholar
Fischer, H. B. 1973 Longitudinal dispersion and turbulent mixing in open-channel flow. Ann. Rev. Fluid Mech. 5, 59–78.Google Scholar
Smith, R. 1979 Calculation of shear-dispersion coefficients. Mathematical Modeling of Turbulent Diffusion in the Environment (ed. C. J. Harris), pp. 343–363. Academic.
Taylor, G. I. 1953 Dispersion of soluble matter in solvent flowing slowly through a tube. Proc. Roy. Soc. A 219, 186–203.Google Scholar