Numerical wetting simulations using the plicRDF-isoAdvector unstructured Volume-of-Fluid (VOF) method

Abstract

Numerical simulation of wetting and dewetting of geometrically complex surfaces benefits from the boundary-fitted unstructured Finite Volume method because it discretizes boundary conditions on geometrically complex domain boundaries with second-order accuracy and simplifies the simulation workflow. The plicRDF-isoAdvector method, an unstructured geometric Volume-of-Fluid (VOF) method, reconstructs the Piecewise Linear Interface Calculation (PLIC) interface by reconstructing signed distance functions (RDF). This method is chosen to investigate wetting processes because of its volume conservation property and high computational efficiency. The present work verifies and validates the plicRDF-isoAdvector method for wetting problems, employing five different case studies. The first study investigates the accuracy of the interface advection near walls. The method is further investigated for the spreading of droplets on a flat and a spherical surface, respectively, for which excellent agreement with the reference solutions is obtained. Furthermore, a validation study using a droplet spreading test case is carried out. The uncompensated Young stress is introduced in the contact angle boundary condition, which significantly improves the validation of the numerical method. Furthermore, a 2D capillary rise is considered, and a numerical comparison based on results from previous work is performed. A suite with all case studies, input data, and Jupyter Notebooks used in this study are publicly available to facilitate further research and comparison with other numerical codes.