A study of capillary flow in a vane -wall gap in zero gravity

A new design high rate drop tower was built and its capability was demonstrated. The high efficiency and low operation cost make it a unique facility for studying of microgravity fluid physics. The relatively short time interval between successive drops provides ample flexibility for experimental study. The performance of the facility was evaluated by estimating the g-residual for the drop test, examining the electro-magnet release mechanism, and determining the centripetal acceleration caused by rotation of the test package during the drop. The facility was also validated by studying resettling of interfaces in circular cylinders after step reduction of the gravity force. Understanding of capillary flow in a vane-wall gap geometry was sought. The geometry is common in the microgravity applications involving, most widely, vane type liquid propellant management devices (PMDs). An analytical method was applied to determine existence of finite-height single-valued equilibrium capillary surface in the chosen geometry by identifying certain critical values. Non-existence of the equilibrium surface implies wetting capillary flow in the gap region and is what a proper PMD requires. Surface Evolver numerical simulation was performed to determine the equilibrium surfaces, identify the critical contact angles, and visualize features of C-singular solution surfaces. Concerning the statics, drop tower experiments were performed to confirm the analytical results. Concerning the dynamics, the experiment results reveal typical feature of the capillary flow in the gap region. Effects of relevant geometric parameters on the capillary flow were studied as well