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Apparent dispersion in transient groundwater flow
Author(s) -
Goode Daniel J.,
Konikow Leonard F.
Publication year - 1990
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr026i010p02339
Subject(s) - mechanics , transverse plane , flow (mathematics) , transient (computer programming) , dispersion (optics) , aquifer , physics , transient flow , steady state (chemistry) , boundary value problem , geology , geotechnical engineering , meteorology , groundwater , optics , chemistry , structural engineering , quantum mechanics , surge , computer science , engineering , operating system
This paper investigates the effects of large‐scale temporal velocity fluctuations, particularly changes in the direction of flow, on solute spreading in a two‐dimensional aquifer. Relations for apparent longitudinal and transverse dispersivity are developed through an analytical solution for dispersion in a fluctuating, quasi‐steady uniform flow field, in which storativity is zero. For transient flow, spatial moments are evaluated from numerical solutions. Ignored or unknown transients in the direction of flow primarily act to increase the apparent transverse dispersivity because the longitudinal dispersivity is acting in a direction that is not the assumed flow direction. This increase is a function of the angle between the transient flow vector and the assumed steady state flow direction and the ratio of transverse to longitudinal dispersivity. The maximum effect on transverse dispersivity occurs if storativity is assumed to be zero, such that the flow field responds instantly to boundary condition changes.