Consistent Boundary Conditions for Age Calculations
1
Institute of Mechanics, Materials and Civil Engineering (IMMC) & Earth and Life Institute (ELI) L4.05.02, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
2
Institute of Mechanics, Materials and Civil Engineering (IMMC), Université Catholique de Louvain, L4.05.02, B-1348 Louvain-la-Neuve, Belgium
3
Freshwater and OCeanic science Unit of reSearch (FOCUS), Sart-Tilman B5a, Université de Liège, B-4000 Liège, Belgium
*
Author to whom correspondence should be addressed.
Water 2020, 12(5), 1274; https://doi.org/10.3390/w12051274
Received: 18 March 2020 / Revised: 22 April 2020 / Accepted: 27 April 2020 / Published: 30 April 2020
(This article belongs to the Special Issue Tracer and Timescale Methods for Passive and Reactive Transport in Fluid Flows)
Age can be evaluated at any time and position to understand transport processes taking place in the aquatic environment, including for reactive tracers. In the framework of the Constituent-oriented Age and Residence time Theory (CART), the age of a constituent or an aggregate of constituents, including the water itself, is usually defined as the time elapsed since leaving the boundary where the age is set or reset to zero. The age is evaluated as the ratio of the age concentration to the concentration, which are the solution of partial differential equations. The boundary conditions for the concentration and age concentration cannot be prescribed independently of each other. Instead, they must be derived from boundary conditions designed beforehand for the age distribution function (the histogram of the ages, the age theory core variable), even when this variable is not calculated explicitly. Consistent boundary conditions are established for insulating, departure and arrival boundaries. Gas exchanges through the water–air interface are also considered. Age fields ensuing from consistent boundary conditions and, occasionally, non-consistent ones are discussed, suggesting that the methodology advocated herein can be utilized by most age calculations, be they used for diagnosing the results of idealised models or realistic ones.
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Keywords:
partial differential equations; boundary conditions; geophysical and environmental fluid flows; reactive transport; interpretation methods; diagnostic timescales; CART; age; age distribution function
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MDPI and ACS Style
Deleersnijder, E.; Draoui, I.; Lambrechts, J.; Legat, V.; Mouchet, A. Consistent Boundary Conditions for Age Calculations. Water 2020, 12, 1274. https://doi.org/10.3390/w12051274
AMA Style
Deleersnijder E, Draoui I, Lambrechts J, Legat V, Mouchet A. Consistent Boundary Conditions for Age Calculations. Water. 2020; 12(5):1274. https://doi.org/10.3390/w12051274
Chicago/Turabian StyleDeleersnijder, Eric; Draoui, Insaf; Lambrechts, Jonathan; Legat, Vincent; Mouchet, Anne. 2020. "Consistent Boundary Conditions for Age Calculations" Water 12, no. 5: 1274. https://doi.org/10.3390/w12051274
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