Towards the shortest possible contact time: Droplet impact on cylindrical superhydrophobic surfaces structured with macro-scale features

Reduced contact time of a droplet impacting on a moving superhydrophobic surface

“…Additionally, at the rebounding moment, the reduced contact time shortens the jumping distance of the droplet. It should be pointed out in the literature that the asymmetric spreading and retraction behaviors of impacting droplets were also reported, not only on the moving hydrophilic 28,30,32 and hydrophobic 29,30,32 flat surfaces but also on the inclined, 19,20,34 curved [21][22][23]35 surfaces or surfaces with macrotextures. 22,24,25 However, the reduction in the contact time resulting from the asymmetric behaviors occurs only on the SHPS.…”

“…It should be pointed out in the literature that the asymmetric spreading and retraction behaviors of impacting droplets were also reported, not only on the moving hydrophilic 28,30,32 and hydrophobic 29,30,32 flat surfaces but also on the inclined, 19,20,34 curved [21][22][23]35 surfaces or surfaces with macrotextures. 22,24,25 However, the reduction in the contact time resulting from the asymmetric behaviors occurs only on the SHPS. [19][20][21][22][23][24][25] For ease of quantifying the dynamic behaviors of impact droplets on the stationary and moving SHPSs, Fig.…”

“…p is the capillary-inertia time and q, R 0 , and r are the droplet density, radius, and surface tension, respectively) of a droplet is almost constant, i.e., t c /t 0 ¼ 2.6 6 0.1. [16][17][18] To reduce this value for achieving the complete rebound, the inclined, 19,20 curved [21][22][23] SHPSs or SHPSs with macrotextures 22,24,25 were considered, and the results amply showed that breaking of the spreading and bouncing symmetry during the impact process play vital roles in shortening the dimensionless contact time. [19][20][21][22][23][24][25][26][27] However, these studies on reducing the droplet contact time were conducted exclusively on stationary SHPSs.…”

Symmetry-Breaking Drop Bouncing on Superhydrophobic Surfaces with Continuously Changing Curvatures

“…Along with the development, recent works have demonstrated asymmetric bouncing dynamics on surfaces with the radius of curvature comparable to drop size, including asymmetric bouncing on tubular surfaces and natural succulent leaves [ 17 ], ribbed-curved surfaces [ 18 ], and cylindrical ridges in millimetric size [ 19 , 20 ]. The shape and size of the cylindrical ridges altered the drops’ behavior significantly, and hence the residence time could reduce further, compared with the dynamics on the flat surfaces.…”

Numerical study of water droplets impacting on cylindrical heat transfer pipes

“…In the retracting stage, the effect of the ratio was taken into account and the theoretical prediction was found to be consistent with the numerical results. Abolghasemibizaki, McMasters, and Mohammadi (2018) found that the time it takes for the droplet to retract along the axial direction of the cylindrical surface determines the duration of the contact time between the droplet and the cylinder. They established a model for the relationship between the contact time reduction and the impact velocity using an experimental method.…”