Inertial coalescence of droplets on a partially wetting substrate

Abstract

We consider the growth rate of the height of the connecting bridge in rapid surface-tension-driven coalescence of two identical droplets attached on a partially wetting substrate. For a wide range of contact angle values, the height of the bridge grows with time following a power law with a universal exponent of 2/3, up to a threshold time, beyond which a 1/2 exponent results, that is known for coalescence of freely-suspended droplets. In a narrow range of contact angle values close to 90°, this threshold time rapidly vanishes and a 1/2 exponent results for a 90° contact angle. The argument is confirmed by three-dimensional numerical simulations based on a diffuse interface method with adaptive mesh refinement and a volume-of-fluid method.

Investigation of droplet coalescence propelled by dielectrophoresis

“…At this stage, h increases at a faster rate for larger actuation potential. Earlier studies have shown that in the inertial regime the growth of liquid bridge (perpendicular to the solid surface) is proportional to τ 1/2 for a contact angle of 90°. Thus, to identify more specific characteristics, the early growth of bridge height is plotted in log–log scale to compare with τ 1/2 proposition at the inset of Figure 5.…”

“…Earlier studies have shown that in the inertial regime the growth of liquid bridge (perpendicular to the solid surface) is proportional to τ 1/2 for a contact angle of 90°. Thus, to identify more specific characteristics, the early growth of bridge height is plotted in log–log scale to compare with τ 1/2 proposition at the inset of Figure 5. A good fit between numerical observations and proves that, up to a certain time period, coalescence happens independently of the electric field influence.…”

Delayed coalescence of surfactant containing sessile droplets

“…The coalescence and interaction of sessile droplets has been the subject of intensive study in scientific literature [1][2][3][4][5][6][7][8][9], not least motivated by its relevance for industrial processes such as ink-jet printing or surface processing. These studies have revealed intriguing and frequently counterintuitive physics behind this ubiquitous process.…”

Morphology evolution and dynamics of droplet coalescence on superhydrophobic surfaces

“…[16][17][18][19] In addition to the dynamics of liquid bridge, there is now the added feature of the motion of a three-phase contact line. [16][17][18][19] In addition to the dynamics of liquid bridge, there is now the added feature of the motion of a three-phase contact line.…”

“…Except for the study of free-droplet coalescence, the coalescence of two droplets on a solid surface is also received much attention. [16][17][18][19] In addition to the dynamics of liquid bridge, there is now the added feature of the motion of a three-phase contact line. A number of studies have shown that the initial conditions, 16 presence of capillary waves, 20 and contact line dissipation 21,22 that influence the dynamics of coalescence.…”