A Mesoscale Study of Forced Convection Induced Solid-Air Dendrite Microstructure Evolution Under Liquid Hydrogen Environment

The air infiltrated into liquid hydrogen is transformed into surface oxygen-rich solid-air dendrites, which poses a huge safety risk to the liquid hydrogen system. In-depth understanding of the microstructure evolution of solid-air dendrites under convection condition is an important issue to control the formation process and composition distribution of solid-air dendrite and avoid risks. In this paper, a six-fold symmetric solid-air dendrite growth numerical model is established for the coupling of flow field, temperature diffusion and solute diffusion during solidification. The lattice Boltzmann method (LBM) is used to calculate the flow field, temperature field, and solute field, and the Cellular Automata model (CA) is used for the growth process of solid-air dendrites. For regular Cartesian grids, a factor is introduced to reduce the anisotropy of grids. The LBM-CA model is used to study the growth rate and morphological evolution of solid-air dendrites in liquid hydrogen environment under forced convection conditions. The results show that the growth rate of each dendrite arm is roughly the same in microgravity, and the dendrite exhibits a six-fold symmetry. Under the condition of forced convection, the morphology of dendrites changes, the growth of upstream dendrites is promoted, and the growth of downstream dendrite arms is suppressed. The mechanism of convection diffusion affecting the growth rate and morphological evolution of solid-air dendrites is introduced in detail.