  The objective of this work is to develop and validate a numerical model to
study wetting during the impact of millimeter-size drops on a flat, smooth,
solid substrate under isothermal or non-isothermal conditions. A finite-element
modeling is used to simulate the transient fluid dynamics and heat transfer,
considering Laplace forces on the liquid-gas boundary. The Lagrangian scheme
allows a very precise tracking of the free surface deformation. In this work,
the numerical model is extended to account for a temperature-dependent
viscosity and for dynamic wetting at the contact line. Numerical results are
presented to study the influence of the kinetic wetting parameter on the
wetting incipience and behavior. Our results show the influence of wetting on
the spreading and the transient drop shape. Also, numerical results are
compared with high-speed visualization, for cases of isothermal and
non-isothermal impact. Matching between simulations and high-speed
visualization allows the determination of the value of the kinetic wetting
parameter. Our main finding is that warm drops spread more than cold drops
because of a reduction of viscous forces, and not because of an increase of
wetting.
