Darcy's Law: q = −(k/μ) ∇P — fluid flux is proportional to permeability k and pressure gradient, inversely proportional to viscosity μ.
Permeability depends on pore geometry. The Kozeny-Carman relation gives k ∝ φ³/(1−φ)² for packed spheres.
The simulation generates a random pore network; pressure is solved by a finite-difference Laplace equation ∇²P = 0 with solid grains blocked. Streamlines trace the flow.