Lattice Boltzmann method analyzing helium bubbles motion in liquid helium

To estimate the cooling capability of liquid helium in a superconducting magnet, it is indispensable to analyze the liquid helium flow and the bubble motion. However, it is almost impossible to understand them by means of the experiment or the numerical calculation based on Navier-Stokes equations. Therefore, we have developed the lattice Boltzmann method to analyze the liquid helium flow and/or the bubble motion in superconducting magnets. In the analysis, the temperature distribution in liquid helium together with the convection was calculated. Then helium vapor bubbles were formed on the heat transfer surface where the temperature was higher than the boiling point. The buoyancy of bubble was taken into account and results in the aggregation of the bubbles. The heat flow in liquid helium could also be calculated. The applicability of this method to the stability analysis of superconducting magnet is also discussed.