Numerical Investigation of Different Dynamic Contact Angle Models for a Droplet Impacting a Surface in OpenFOAM

Computational Fluid Dynamics (CFD) is used to study the spreading processof a water droplet with a radius of ۰.۰۰۲۷۵mm impacting a wax surface at avelocity of ۱.۱۸ms−۱. This type of flow is considered to be Multiphase,incompressible, laminar, surface tension dominated and is governed by theNavier stokes and continuity equations. To accurately model the spreadingprocess ۳ different contact angle models are investigated, two of which takeinto account the moving contact line. The governing equations are solved usingthe open source C++ library OpenFOAM, which uses a Finite Volume Method(FVM) of discretization and a Volume Of Fluid (VOF) interface capturingmethod. The VOF method is known to produce unphysical velocities whenhigh pressure gradients exist between the two phases, thus a numericalimprovement is implemented to reduce the magnitudes of the unphysicalvelocities. The improvement reduces the magnitudes of the unphysicalvelocities and as shown in literature their magnitudes increase with an increasein surface tension dominance. The improvement is implemented together withdifferent contact angle models and results obtained show that contact anglemodels that take into account the moving contact line gives a good correlationof the spreading diameter obtained numerically with the one obtainedexperimentally.