36 2 Simulating Steady-State Natural Convective Problems 13 (t = 6 × 10 13 s) (t = 7 × 10 s) 13 (t = 8 × 10 13 s) (t = 9 × 10 s) 14 (t = 1 × 10 14 s) (t = 1.1 × 10 s) Fig. 2.18 Particle trajectories in the porous medium (Case 2)