Lattice Boltzmann Models for Flow and Transport in Saturated Karst

Abstract

Flow and transport simulation in karst aquifers remains a significant challenge for the ground water modeling community. Darcy's law-based models cannot simulate the inertial flows characteristic of many karst aquifers. Eddies in these flows can strongly affect solute transport. The simple two-region conduit/matrix paradigm is inadequate for many purposes because it considers only a capacitance rather than a physical domain. Relatively new lattice Boltzmann methods (LBMs) are capable of solving inertial flows and associated solute transport in geometrically complex domains involving karst conduits and heterogeneous matrix rock. LBMs for flow and transport in heterogeneous porous media, which are needed to make the models applicable to large-scale problems, are still under development. Here we explore aspects of these future LBMs, present simple examples illustrating some of the processes that can be simulated, and compare the results with available analytical solutions. Simulations are contrived to mimic simple capacitance-based two-region models involving conduit (mobile) and matrix (immobile) regions and are compared against the analytical solution. There is a high correlation between LBM simulations and the analytical solution for two different mobile region fractions. In more realistic conduit/matrix simulation, the breakthrough curve showed classic features and the two-region model fit slightly better than the advection-dispersion equation (ADE). An LBM-based anisotropic dispersion solver is applied to simulate breakthrough curves from a heterogeneous porous medium, which fit the ADE solution. Finally, breakthrough from a karst-like system consisting of a conduit with inertial regime flow in a heterogeneous aquifer is compared with the advection-dispersion and two-region analytical solutions.

Lattice Boltzmann modeling for tracer test analysis in a fractured Gneiss aquifer

“…The first component was the fluid and the second component was a passive scalar. This component behaves as a passive component having no velocity and is advected by the background fluid [29,37,42,43]. LBM was used in the interpretation of the monitoring data from the natural gradient tracer test.…”

Lattice Boltzmann Modeling of Classic Solute Transport Boundary Value Problems

“…The nondimensional pore volume parameter ( T ) is only applicable to scale time when Pe > = 1; otherwise, diffusion length is a recommended nondimensional parameter for time scaling. Note that the coupled flow and solute transport models used in this study have been applied to simulate more complex breakthrough curves in karst aquifers (Anwar et al, 2008; Anwar and Sukop, 2009).…”

Large‐Scale Experiments on the Formation of Surface Vortices with and without Vortex Suppression

“…The development and strength of gas‐core vortices in pump intakes is challenging to predict, due to the huge variety of possible intake geometries, sizes and inflow conditions as well as the complex fluid dynamic phenomena occurring during vortex formation. Intensive investigations on the vortex formation in varying scales have been conducted by Anwar , , Daggett & Keulegan , Jain et al , Rindels and Gulliver , and Hecker . Large‐scale particle image velocimetry measurements have already been made by Keller et al, but in a setup with horizontal intake orientation .…”