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

TL;DR

This study develops a numerical model to analyze how temperature affects wetting and spreading of millimeter-sized water drops impacting a flat substrate, validated by high-speed visualization experiments.

Contribution

The paper introduces an extended finite-element model that accounts for temperature-dependent viscosity and dynamic wetting, providing new insights into impact behavior under non-isothermal conditions.

Findings

Warm drops spread more than cold drops due to reduced viscous forces.

Numerical results match high-speed visualization, validating the model.

Wetting influences spreading and transient drop shape.

Abstract

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.