Mesoscopic-scale study of convection-induced morphological evolution of solid-air dendrites in liquid hydrogen

The trace amount of air infiltration that may occur during the utilization of liquid hydrogen may be confronted with a severe security risk. Considering the effect of convection, a six-fold symmetric solid-air dendrite growth numerical model is established for the coupling of flow field, temperature field and solute field during solidification process. For regular Cartesian grids, a factor is introduced to reduce the anisotropy of grids, and its validity is verified. The reliability of the model is evaluated by comparing the numerical results of the growth of ice-dendrite with the same face-centered cubic structure with the experimental results, and the subsequent numerical results of solid-air dendrites growth rate match well with the results of analytical theory. On this basis, the growth characteristics of solid-air dendrites under diffusion condition and natural convection and forced convection conditions are studied. The results show that the tip of each dendrite arm has a consistent growth rate under diffusion condition, and the dendrites present a six-fold symmetric morphology. The dendrite growth is promoted in the upstream and inhibited in the downstream under both natural convection and forced convection conditions, and the morphology of the reshaped dendrites lose symmetry. Forced convection promotes upstream more than it inhibits downstream. The mechanism of the two conditions affecting the growth of solid-air dendrites and the differences between them are explained in detail.