In this work, we
have developed a model to describe the behavior
of liquid drops upon impaction on hydrophobic particle bed and verified
it experimentally. Poly(tetrafluoroethylene) (PTFE) particles were
used to coat drops of water, aqueous solutions of glycerol (20, 40,
and 60% v/v), and ethanol (5 and 12% v/v). The experiments were conducted
for Weber number (We) ranging from 8 to 130 and Reynolds
number (Re) ranging from 370 to 4460. The bed porosity
was varied from 0.8 to 0.6. The experimental values of βmax (ratio of the diameter at the maximum spreading condition
to the initial drop diameter) were estimated from the time-lapsed
images captured using a high-speed camera. The theoretical βmax was estimated by making energy balances on the liquid drop.
The proposed model accounts for the energy losses due to viscous dissipation
and crater formation along with a change in kinetic energy and surface
energy. A good agreement was obtained between the experimental βmax and the estimated theoretical βmax. The
proposed model yielded a least % absolute average relative deviation
(% AARD) of 5.5 ± 4.3 compared to other models available in the
literature. Further, it was found that the liquid drops impacting
on particle bed are completely coated with PTFE particles with βmax values greater than 2.
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