Numerical simulation of a drop impact on a superhydrophobic surface with a wire

Superhydrophobic surfaces patterned with macroscale (≈1 mm) structures have gained increasing interest in the past years because of their potential in reducing the contact time between impacting liquid drops and the solid surface. The reduced wettability of these surfaces is of interest in numerous technical applications, as, for example, in anti-icing on airplane wings. Several experimental studies have been carried out on this topic in the literature; on the other hand, only very limited numerical investigations are available in the literature. In this paper, we present a numerical study based on a volume of fluid code for direct numerical simulation of incompressible multiphase flows. A necessary condition for the realization of this study was the implementation of arbitrary-shaped boundaries using a Cartesian grid system. Our implementation of embedded boundaries is based on a volume fraction representation of the boundaries and on a piecewise linear approximation of their surface. The discretized boundaries are then cut off from the computational domain, leading to an altered formulation of the discretized governing equations. To validate the method, we show simulation results for different impact velocities for the case of a droplet impacting on a wire, which has been investigated experimentally in the literature. The simulations show good agreement in terms of contact time and impact morphology, thus, showing the validity of the implementation. Moreover, an extensive analysis of the velocity field for this setup is presented, helping us to better understand the underlying physical phenomena.