DYNAMIC CONTACT ANGLE MODEL WITH A VOF METHOD WITHIN OPENFOAM

Abstract

The interaction of sloshing liquid propellant with the rigid body dynamics of the spacecraft or launch vehicle is of crucial importance throughout the whole mission and must be mastered by the reaction control system. It is therefore indispensable to be capable to predict the fluid behavior in all mission phases. A particular challenge is the change from the thrust phase to the ballistic phase, when the capillary forces become dominant. The reorientation process of the propellant is then driven by the contact line behavior and within the transition phase by the dynamic contact angle. A dynamic contact angle model is developed and validated with a benchmarked upon step reduction in gravity [1]. The model is implemented in the CFD OpenFOAM framework using the volume of fluid method (VOF). The results reveal the importance and contribution of the contact line behavior in case of free surface dynamics at microgravity conditions. With the developed contact angle model full-wetting liquids (zero degree contact angle) can be modeled. The CFD results show very good agreement with the experimental data and will be presented. In the next step the dynamic contact angle model will be further developed to consider thermal effects at the contact line.