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- Painter, Scott L., et al.
(författare)
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Time-domain random-walk algorithms for simulating radionuclide transport in fractured porous rock
- 2008
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 163:1, s. 129-136
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Tidskriftsartikel (refereegranskat)abstract
- Time-domain random-walk (TDRW) algorithms are efficient methods for simulating solute transport along one-dimensional pathways. New extensions of the TDRW algorithm accommodate decay and ingrowth of radionuclides in a decay chain and time-dependent transport velocities. Tests using equilibrium sorption and matrix diffusion retention models demonstrate that the extended TDRW algorithm is accurate and computationally efficient. When combined with stochastic simulation of transport properties, the resulting algorithm, Particle on Random Streamline Segment (PORSS), also captures the effects of random spatial variations in transport velocities, including the effects of very broad velocity distributions. When used in combination with discrete fracture network simulations, the PORSS algorithm provides an accurate and practical method for simulating radionuclide transport at the geosphere scale without invoking the advection-dispersion equation.
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| 2. |
- Painter, Scott, et al.
(författare)
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Time domain particle tracking methods for simulating transport with retention and first-order transformation
- 2008
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 44:1
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Tidskriftsartikel (refereegranskat)abstract
- Particle tracking in the time domain has received increasing attention as a technique for robustly simulating transport along one-dimensional subsurface pathways. Using a stochastic Lagrangian perspective, integral representations of transport including the effects of advection, longitudinal dispersion, and a broad class of retention models are derived; Monte Carlo sampling of that integral leads directly to new time domain particle tracking algorithms that represent a wide range of physical phenomena. Retention-time distributions are compiled for key retention models. An extension to accommodate linear transformations such as decay chains is also introduced. Detailed testing using first-order decay chains and four retention models (equilibrium sorption, limited diffusion, unlimited diffusion, and first-order kinetic sorption) demonstrate that the method is highly accurate. Simulations using flow fields produced by large-scale discrete-fracture network simulations, a transport problem that is difficult for conventional algorithms, demonstrate that the new algorithms are robust and highly efficient.
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| 3. |
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