Analysis of column tracer experiments by a stochastic-convective transport method
Recent research into the mechanisms of solute transport in porous media on a field-length scale has indicated that a transport description in terms of a stochastic-convective flow equation provides a more adequate approach than the conventional convection-dispersion equation, because the latter equation fails to describe transport in hydrogeologic systems for which hydrodynamic dispersion is non-Fickian. Stochastic transport methods require prior estimation of a statistical mean and spatial covariance of the flow velocity, instead of a dispersive parameter. A stochastic-convective transport formulation based upon solute travel time probability is presented and is shown to include Fickian transport as a special subcase. It is further demonstrated that a travel time probability associated with a log-normal distribution of hydraulic conductivity will yield concentration breakthrough curves nearly equivalent to Fickian transport when the coefficient of variation in travel time is sufficiently small. (less than or equal to 1). Applied to column tracer experiments the results suggest that typical laboratory measured hydrodynamic dispersion may be ascribed to local variations in hydraulic conductivity. The travel time formulation is shown to provide a direct link between measured dispersivity and the autocovariance of local flow velocity variation, which can be a consequence of media inhomogeniety and the system boundary conditions. Dispersivity is shown to manifest a scale effect by increasing in proportion to the length of a system when the velocity correlation range is greater than the length. Chemical absorption effects are described by simply scaling the travel time probability with a retardation factor.
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 6313764
- Report Number(s):
- PNL-SA-9478; CONF-810761-1; ON: DE81030088
- Country of Publication:
- United States
- Language:
- English
Similar Records
Stochastic-convective transport with nonlinear reaction: Mathematical framework
Stochastic-convective ensemble method for representing dispersive transport in groundwater
Related Subjects
580100* -- Geology & Hydrology-- (-1989)
AQUEOUS SOLUTIONS
CONVECTION
DIFFUSION
DISPERSIONS
DISTRIBUTION
ENVIRONMENTAL TRANSPORT
FLUID FLOW
GROUND WATER
HYDROGEN COMPOUNDS
HYDROLOGY
ISOTOPE APPLICATIONS
MASS TRANSFER
MATERIALS
MIXTURES
NATURAL CONVECTION
OXYGEN COMPOUNDS
POROUS MATERIALS
SOLUTIONS
STOCHASTIC PROCESSES
TIME DEPENDENCE
TRACER TECHNIQUES
VELOCITY
WATER