Static analysis and contact angle hysteresis study of bubbles in Chinese space station tank models under different gravity effects

In most space shuttle fuel tanks, a central column is used to secure the Propellant Management Devices. This study focuses on the distribution of fluids in such tanks. Microgravity experiments are conducted on the Chinese Space Station, and annular bubbles surrounding the central column have been observed for the first time. An in-depth study is carried out on the distribution and profile of these bubbles using perturbation methods and the Young–Laplace equation. Theoretical values for the gas–liquid interface morphology of annular bubbles under different gravity levels are obtained and compared with numerical simulation results, showing substantial agreement. The phenomenon of contact angle hysteresis of bubbles under gravity conditions was studied through simulation and theoretical analysis. Detailed analysis of the characteristics of contact angle hysteresis and corresponding drag resistance using the Wenzel model was carried out. Based on this, a numerical calculation program based on the shooting method was developed to obtain the morphology of the same bubble under different gravities. Furthermore, it was found that the theoretical maximum Bond number for circular bubbles suspended on the central column is 2, and it was observed that bubbles with equilibrium contact angles closer to 90° exhibit greater upward displacement of their centroids under varying gravity, providing theoretical support for bubble management in aerospace engineering.