Computational Fluid Dynamics Analysis of Jet-Ullage Interactions During Microgravity Mixing

Forced jet mixing with and without cooling has long been proposed for active pressure control of cryogenic tanks in microgravity. In this paper, a three-dimensional two-phase computational fluid dynamics (CFD) model is presented that was developed to capture the intricate dynamic interaction between a forced liquid jet and the ullage interface under weightlessness conditions. The CFD model is validated against the microgravity results of the Tank Pressure Control Experiment. The volume-of-fluid method is used to capture the ullage deformation as well as movement in the jet mixing simulations of the microgravity experiment. Two different initial ullage positions are considered, and computational results for the jet–ullage interaction are compared with a still-image sequence captured from real-time video of the experiment. Parametric simulations over a range of jet Weber numbers indicate four distinct jet–ullage interaction modes from nonpenetrating to fully penetrating, which are corroborated experimentally. Qualitative comparisons also provide good agreement between CFD predictions and experimental results with regard to the main features of the ullage dynamics, such as movement, deformation, and jet penetration during microgravity mixing.