As the surface tension of cryogenic fluids in deep low-temperature space is much smaller, the capillary driven by surface tension is weakened under microgravity, which is influenced by many factors, including the working fluid properties, the wettability of capillary surface, and the geometrical properties of tube (cross-sectional shape, equivalent diameter, wetted perimeter, etc.). So it is necessary to study the flow behaviors of low temperature working fluid driven by surface tension under microgravity. In the paper, fluid behaviors under influencing factors (including tube sizes, lowtemperature working fluid properties, initial liquid volumes, etc.) of cryogenic capillary-flow under microgravity are studied numerically by developing a 2D numerical simulation of vertical capillary tube. In the process of direct numerical simulation, the interface between two phases is represented by a boundary and has no thickness which is described through the moving mesh interface method. To verify accuracy and rationality of this numerical method, the capillary height of interphase between water and air at room temperature in the gravity field is tested firstly, in which the relative results prove that the accuracy and rationality of this numerical method here. Then, the numerical simulation is carried out for four working cases, which is also analyzed in detail. The work in this paper can provide effective verification and analysis means for subsequent experiments and theoretical models.
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