| dc.description.abstract | When droplets impact a liquid pool, they may undergo some processes such as coalescence,
floating, splashing, and bouncing. The bouncing phenomenon significantly affects various
technological applications such as engine fuel injection, inkjet printing, and inkjet coating. This
study focuses on the bouncing behavior of droplets upon liquid pools at different impact
velocities and increasing pool temperatures. The droplets and liquid pools were of the same
silicon oil.
We conducted the experiments on various aspects, including the penetration time,
bouncing time, bouncing period, settling time, surface wave, and residence time, in response to
changes in experimental conditions. The penetration time, bouncing time, bouncing period, and
settling time were unrelated to the Weber number and temperature difference between the
droplet and liquid bath. The penetration and bouncing times increased with an increase in
droplet diameter, and the bouncing period and settling time exhibited a slight increase with
increasing droplet diameter. The wave speed was unrelated to the Weber number, diameter, and
temperature difference. On the other hand, the residence time increased with an increase in
temperature difference and showed an increasing trend with increasing impact velocity, with
only a few exceptions in the results.
Further analysis of the experimental data through dimensionless analysis revealed that the
dimensionless penetration time scaled by capillary time
th
reduced to a constant. The
dimensionless bouncing time, bouncing period, and settling time slightly decrease with an
increase in droplet diameter. The dimensionless wave speed fell between the surface tension
wave phase and group velocities. To analyze the influence of thermocapillary flow on droplet
floatation, we introduced a delay time
d
indicating the increase in residence than the uniform
temperature case and defined the Marangoni number based on the temperature difference. The
results showed that
/ d th
increases with the increase in
Ma . The dimensionless delay time,
iii
however, is unrelated to droplet diameter and velocity. Experimental results revealed that
increased bath temperature had no impact on the short-term behaviors of droplet bounce but
prolonged the droplet floatation above the bath. | en_US |