Transport in three-dimensionally heterogeneous aquifers: 1. Dynamics of concentration fluctuations
- Massachusetts Institute of Technology, Cambridge, MA (United States)
The concentration variance, i.e., mean squared concentration fluctuations, undergoes mean advection, a local dispersive flux, and a microdispersive flux due to a correlation between squared concentration perturbations and velocity perturbations. The products of the macrodispersion coefficient and the squared gradient of the mean concentration field determine the rate of production of concentration variance. The rate of dissipation of concentration variance is determined by the product of the local dispersion coefficient and the mean squared gradient of the concentration perturbation field. Variance dissipation is represented as a first-order decay with the decay coefficient equal to twice the sum of the local dispersion coefficient divided by the squared concentration microscale. The concentration microscale, is an increasing function of the log conductivity microscale. Thus the larger the log conductivity and vice versa. The wave number squared dependence of fluctuation dissipation requires intensive sampling to realistically model the log conductivity spectrum and its microscale, which determines the rate of dissipation of concentration fluctuations by the action of local dispersion. There is no mechanism of destroying concentration fluctuations without the action of local dispersion. 39 refs., 6 figs.
- OSTI ID:
- 186103
- Journal Information:
- Water Resources Research, Vol. 30, Issue 6; Other Information: PBD: Jun 1994
- Country of Publication:
- United States
- Language:
- English
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