FIG. 4 . No-coalescence-rebound regime (NCR). (a) Selected image sequence of impact and rebound behaviors of two droplets on a flat superhydrophobic surface with L =2.00 and We =35. The velocity fields are extracted along the mid y (b) and the midx (c) plane passing through the box. The normalized time is defined asτ =t /(ρR 03/)1/2.