  Existing energy balance models, which estimate maximum droplet spreading,
insufficiently capture the droplet spreading from low to high Weber and
Reynolds numbers and contact angles. This is mainly due to the simplified
definition of the viscous dissipation term and incomplete modeling of the
maximum spreading time. In this particular research, droplet impact on a smooth
sapphire surface is studied for seven glycerol concentrations between 0% -
100%, and 294 data points are acquired using high-speed photography. Fluid
properties such as density, surface tension, and viscosity are also measured.
For the first time according to the authors' knowledge, we incorporate the
fluid viscosity in the modeling of the maximum spreading time based on the
recorded data. We also estimate the characteristic velocity of the viscous
dissipation term in the energy balance equation. These viscosity-based
characteristic scales help to formulate a more comprehensive maximum droplet
spreading model. Thanks to this improvement, our model successfully fits the
data available in the literature for various fluids and surfaces compared to
the existing models.
