Coalescence-induced droplet jumping on superhydrophobic surfaces with non-uniformly distributed micropillars

Coalescence-Induced Droplet Jumping on Superhydrophobic Surfaces with Annular Wedge-Shaped Micropillar Arrays

“…In contrast, the pressure along the y -direction was distributed asymmetrically, resulting in an unbalanced force driving the droplet’s motion in the y -direction and making the droplet jump from the trapezoidal bottom edge of the micropillar to the top edge. The relative transport distance L t / R d of the droplet in the gradient direction was defined as the ratio of the transport distance to the initial droplet radius when air resistance was neglected , L normalt R normald = 2 v y , normalj v z , normalj R d g where v y ,j and v z ,j are the gradient-direction velocity and vertical velocity of the droplet center of mass at the departure time. The relative transport distance L t / R d was calculated to be 4.5 when R d / W 2 = 1.75, substantially greater than the relative transport distance of 0.3 when R d / W 2 = 3.75.…”

“…To further investigate the influence of the relative size and position of the droplets and micropillars on droplet jumping, interFoam, , a multiphase flow solver based on the VOF (volume of fluids) method in OpenFOAM software, was used to simulate the coalescence-induced droplet jumping process on the surface with annular wedge-shaped micropillar arrays. Experiments found that the relative positions of the droplets and micropillars mainly included two kinds: the droplet center-of-mass line was parallel (i.e., along the x -direction) and perpendicular (i.e., along the y -direction) to the trapezoidal bottom edge of the wedge-shaped micropillar.…”