Research Project C01

We investigate the flow structure and the porosity-permeability relationship of porous media that undergo morphology modifications due to evaporation or microbially induced calcite precipitation, as well as wettability modifications of the solid-fluid interface due to fluid pH, composition, or salt concentration changes. We develop simulation methods based on coupled multi-phase and multi-component Lattice-Boltzmann and molecular dynamics simulations, capable of reproducing these processes in detail on the pore scale, yielding results to be used to improve existing continuum models.

In the first funding period, we established a multi-physics simulation framework by integrating a multiphase/multicomponent lattice Boltzmann method with electrokinetics (LB-EK). Using automatic code generation, we implemented the Shan-Chen pseudopotential model with tunable wetting and no-slip boundary conditions, and coupled it to a finite-volume electrokinetics solver to simulate dilute charged solutes interacting with multicomponent flows. In parallel, we developed an agent-based bacterial model capturing run-and-tumble motility calibrated to E. coli dynamics, as well as reversible surface attachment under flow (see Figure 1).

In the second funding period, we developed a precipitation model within the LB-EK framework, combining stochastic nucleation and crystal growth with an evaporation model to investigate salt crust formation. These simulations allowed us to analyze how wettability and capillary forces drive precipitation patterns, laying the groundwork for improved multi-scale integration. In parallel, we advanced biofilm modeling by coupling bacterial motility with flow fields and surface attachment mechanics (see Figure 2). These agent-based simulations revealed critical mechanisms behind early-stage biofilm formation and microbial transport efficiency in porous media, reproducing key experimental trends from research project C04. Atomistic simulations provided new insights into interfacial water dynamics and NMR relaxation behavior, supporting experimental NMRD data from research project C05 (see Figure 3). In addition, we collaborated with research project A01 on developing a generalized entropy scaling model by employing classical density functional theory, combined with a novel viscosity reference that accounts for the influence of solid–fluid interactions on fluid viscosity.

In FP3, we will continue our effort to combine physical insights obtained on multiple scales in order to derive a multi-scale precipitation model for porous media. As a key contribution to the CRC’s salt vision, we analyse both the precipitation kinetics and the precipitate structure on a molecular scale. To further connect our simulations to experimental data we will continue our efforts to characterize experimental salt structures. This will be accomplished by bridging precipitation from the molecular to the pore scale by treating the solvent particles implicitly through machine-learned coarse-grained implicit solvent (MLCG-IS) potentials. Coupling precipitation to evaporation is tackled building upon our LB-EK approach, which we will refine using information from the molecular scale. Contributing to biomineralization benchmark, we will include pH variations for the induced precipitation for the urease induced urea splitting. We will further refine our biofilm model to study biofilm clogging in  microfluidic experiments, in close collaboration with C04 and Z02.