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Solute transport and absorption in porous media
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Resumo(s)
The transport of a solute in a solvent is an advection-diffusion problem that is widespread in both
nature and industry. Many porous materials, such as soils and rocks, are intrinsically disordered at the
pore scale which results in complex flow patterns. In this work, the dynamics of the fluid and solute was
simulated using the lattice-Boltzmann method (LBM) to investigate how solute dispersion and absorption
are affected by the porous medium properties. We simulate systems with circular obstacles to represent
the pore scale and obtain the macroscopic source term for different microscopic properties. We validated
our code for advection, diffusion, and absorption in porous media. First, we validated the model for the
dispersion in a Poiseille flow by confirming that the theoretical prediction between the effective diffusion
and Peclet number holds true in our simulations. Similarly, we simulated the solute dispersion in a ´
regular grid of circular objects to analyze the relationship between these two quantities. Additionally,
we considered a system with no advection, only diffusion and absorption at a constant rate our results
were according with the theoretical expectation and we verified that the relative error becomes smaller
for larger obstacles (finer discretization). We also studied a regular porous medium with and without
saturation for advection, diffusion, and absorption. In systems with saturation, we found out that the
solute concentration decays exponentially while in the case of constant absorption, solute concentrations
decrease linearly. For the same conditions we also discovered that the amount of solute lost per obstacle
is constant for systems without saturation, whereas the proportion of solute lost is not. We found that the
exponential decay of the concentration as a function of distance in disordered porous media is similar to
that of regular porous media with the same simulation parameters.
Descrição
Tese de Mestrado Integrado, Engenharia Física , 2022, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Lattice Bolztmann Meios porosos Dispersão Absorção de soluto Teses de mestrado - 2022