Non-isothermal wetting during impact of millimeter size water drop on a flat substrate: numerical investigation and comparison with high-speed visualization experiments

摘要

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