Speaker
Description
Heterogeneous porous media saturated with two liquid phases represent a complex system that can be observed in many engineering and natural processes. The transport of passive solutes in this type of environment is at the centre of our research whose final goal is to quantify and mathematically describe the physical mechanisms that regulate the displacement of the solute, such as stretching and twisting. To quantify and analyse the dynamics of the solute mixing and the dispersion, we perform numerical simulations where passive solute is transported by two fluids through a heterogeneous porous media, such as an aquifer or a reservoir. Based on the mutual miscibility of the fluids two main scenarios are identified, one where the fluids that transport the passive solute are miscible and one where they are immiscible. In both cases the passive solute can freely cross the interface between the two fluids. The setup for the numerical experiment is a three-dimensional flow and transport domain where permeability is represented by a multi-Gaussian random field characterised by an exponential covariance function. We prescribe the mean flow while periodic conditions are applied to the permeability on the lateral boundaries. The injection of the less viscous into the domain saturated with a more viscous fluid happens along a control plane perpendicular to the mean flow direction. The displacement of the more viscous fluid by a less viscous fluid leads to fingering instabilities. The flow fluctuations are governed by the unstable displacement of the two fluids and the spatial heterogeneity. In order to study the mixing of a passive solute in this flow, we consider an instantaneous solute injection over the control plane at time zero. For both scenarios, the solute dispersion is quantified in terms of the spatial moments of the solute distribution, mixing in term of the scalar dissipation rate, dilution index, and the probability density function of concentration point values. Mixing metrics that show regular trends are fitted using power and exponential laws. Compared to the constant viscosity case, the viscosity difference between the liquid phases enhances the mixing of the passive solute.
| Country | Spain |
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