The intensity distribution (top-left) of all pores (solid) can be fitted with two Gaussians, i.e., a dark component with μ₁ = 0.62 I₀ and σ₁ = 0.14 I₀ (dashed) and a bright component with μ₂ = 0.80 I₀ and σ₂ = 0.04 I₀ (dash-dotted). The gray region outlines the bright component as given by the optimal thresholds T₁ = 0.76 I₀ and T₂ = 0.87 I₀. The frequency distributions are also given for the flow speed (top-right), the divergence (bottom-left), and the vorticity (bottom-right) within all pores. The three vertical lines mark the position of the median (solid), mean (long-dashed), and 10th percentile (dash-dotted) of the the speed v, the divergence ∇  ·v, and the vorticity ∇  ×  v. The divergence and vorticity distributions are fitted with a Gaussian (dashed) having a mean value of μ =  −0.14 × 10^-3 s^-1 and −0.01 × 10^-3 s^-1, respectively.