Time dependent dispersion in macro scale heterogeneous porous media
Due to the difficulty of characterizing complex heterogeneities with mathematical equations, the analytical solution based on the convection-dispersion equation assumes dispersion that is independent of time and space. However, moreestablished results suggest that dispersion varies with space due...
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| Main Authors: | , |
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| Format: | Article |
| Published: |
2002
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| Online Access: | http://journalarticle.ukm.my/1393/ http://www.ukm.my/jkukm/index.php/jkukm |
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| Summary: | Due to the difficulty of characterizing complex heterogeneities with mathematical
equations, the analytical solution based on the convection-dispersion equation
assumes dispersion that is independent of time and space. However, moreestablished
results suggest that dispersion varies with space due to the complexity of a porous
structure and the effect of large e heterogeneities in the field. This space dependence
of dispersion has been considered as the primary reason for the "scale-up" problem,
which is disparity between laboratory and field measured dispersion. In this work, the
space dependence of dispersion is converted to time dependence by considering the
fact that distance x = nt and K(x) = (nt) = nK(t) since average velocity flow is
considered. Results from this work demonstrate that space or time independence of
dispersion only occurs at relatively long duration of flow where the flow is generally
stabilized and small values of fractal exponent. The concentration profile in a porous
system assuming constant and time dependent dispersion is also evaluated |
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