Effect of dynamic contact angle models on the droplet spread simulation

Abstract

Many industrial processes such as inkjet printing, spray coating and spray cooling, involve the liquid droplets impacting onto solid surfaces. Hence, an accurate estimation of the impact of a droplet onto a solid surface is of great importance because unexpected behaviors of droplets may result in bad quality products or services. In order to make an accurate numerical simulation, one needs to solve many challenging problems such as interface localization and the estimation of dynamic contact angle (DCA). There are many techniques developed for the localization of the phase interface in two phase flows. The most popular techniques are the level set, the volume of fluid (VOF) and the Lagrangian methods. The Lagrangian methods are computationally expensive, and the level set method is not mass conservative. Therefore, in this work we have selected the VOF method and conducted our simulations using two different interface capturing schemes, an algebraic algorithm named Multidimensional Universal Limiter for Explicit Solution and a geometrical algorithm named IsoAdvector. We have compared four DCA models, the Quasi-Dynamic, the Shikhmurzaev, the Kistler and the Bracke models. We have used OpenFOAM, an open source computational fluid dynamics (CFD) software as our computation platform. We have implemented the DCA models and used them as a boundary condition for the phase fraction equation, which is used by the VOF method in order to locate the phase interface. Numerical simulations were compared with five different experimental results. The performances of the simulations were evaluated using two metrics, the mean spread factor error and the maximum spread diameter error. Even though the performances of the DCA models are similar, for higher Reynolds numbers, the Shikhmurzaev model gave the most accurate results, whereas the Kistler model and the Quasi-Dynamic model gave better estimations in low Reynolds numbers. We've also concluded that the IsoAdvector scheme is not suitable for the droplet impact simulations with low Weber numbers.