Digital rock physics has been in use for the last 30 years as a method to extract petro-physical properties from digital scans of reservoir rocks or reservoir rocks analogs. This is a multi-stage process that includes collection of representative samples, digitalization of the rock’s pore space and numerical simulations of the physical properties we want to study.
One challenge, from the numerical simulation perspective, is that simulating how fluid flows inside the rock is very computational demanding, so that we want to use fast fluid solvers. A problem with these solvers for intermittent flooding scenarios is that they exaggerate compressible effects in fluid simulations for complex geometries, like porous media, and can even induce spurious acoustic phenomena.
The top subfigure shows the magnitude of a force field representing a pressure driven flow. Note how the force magnitude adapts to the pore geometry. The bottom subfigure shows the associated velocity field.
A standard method to remove these unwanted effects is to use an implicit numerical solver, which is the natural choice for stationary problems. However, for dynamic systems, where boundary pressures and/or fluxes change rapidly, implicit solvers can impose a heavy computational burden.
In the article “A generalized bodyforce scheme for lattice Boltzmann simulations of incompressible flow in complex geometries” we describe a faster method for solving incompressible multi-phase fluid flow problems, which works well within CSSR’s focus on intermittent flooding scenarios.
Lead author, Espen Jettestuen (WP1 leader)
Our method is a generalization of the well-established forcing method, which is used to induce flow where the inlet and outlet are positioned opposite of each other in a regular computational domain. In this paper, we show that our method performs well for general complex geometries with multiple open boundaries. We also show that our method improves the simulation of systems where the standard forcing scheme is applicable. The only increase in computational time is during the initialization step, so there are no additional costs at run-time.
Jettestuen, Espen; Aursjø, Olav; Vinningland, Jan Ludvig; Hiorth, Aksel. A generalized bodyforce scheme for lattice Boltzmann simulations of incompressible flow in complex geometries. Physics of Fluids, 35, (2023).