Contours of the entropy of mixing at time instants t = 0.5, 1.0, 2.0, and 3.0, respectively. The four columns, from left to right, correspond to the relaxation times τ 1 = 10 − 4 , τ 2 = 2 × 10 − 4 , τ 3 = 4 × 10 − 4 , and τ 4 = 8 × 10 − 4 , respectively.