On the symmetry of the age field of a passive tracer released into a one-dimensional fluid flow by a point-source
Deleersnijder, E.; Delhez, E.J.M.; Crucifix, M.; Beckers, J.-M. (2001). On the symmetry of the age field of a passive tracer released into a one-dimensional fluid flow by a point-source. Bull. Soc. r. Sci. Liège 70(1): 5-21 In: Bulletin de la Société Royale des Sciences de Liège. Société Royale des Sciences de Liège: Liège. ISSN 0037-9565; e-ISSN 1783-5720, more |  |
| Keywords | Age
Motion > Fluid motion > Fluid flow
Symmetry
Symmetry
Tracers
Transport processes > Advection
Marine/Coastal |
| Abstract | Tracer is released from a point-source into an incompressible, one-dimensional fluid flow, with constant velocity and diffusivity. The age of a tracer parcel, which is defined as the time elapsed since leaving the source, may be evaluated as the ratio of the age concentration to the tracer concentration. The latter are governed by two partial differential equations. Time-dependent analytical solutions are derived, which show that the age is symmetric with respect to the source. This is astonishing, since it could have been expected that the age would reflect somehow the strong asymmetry of the tracer concentration, which tends to be much larger on the downstream side of the source than on the upstream side. Some finite-difference counterparts of this problem are seen to lead to age fields which, in their steady-state limit, are also symmetric with respect to the source. This is believed to be helpful to interpret the results of numerical models of complex fluid flows in which the age is introduced as a diagnostic variable. |
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