Biomedical Engineering Reference
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Figure 1. Impact morphology of shear-thinning drops (equilibrium diameter: 3.4 mm), on a parafilm
substrate from a fall height of 50 mm [16].
influence the impacting drop dynamics. From Fig. 1 it seems that an increase of
the power law index increases the maximum spreading diameter, and this would
be against the fact that, on the contrary, for lower power law index, the viscosity
will be lower for high velocity gradients (at the beginning of the impact for exam-
ple) and, since the viscous dissipation is related to maximum spreading, this will
cause less dissipation and then a greater spreading diameter. Equivalent impacts of
shear-thinning drops on glass and parafilm substrates are very similar during the
inertial expansion phase, as shown in Fig. 2, which displays the dimensionless drop
diameter, β , with respect to time for different impact Weber numbers.
Significant differences can only be observed after maximum inertial spread:
drops impacting on the hydrophobic surface exhibit a clear retraction stage, which
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