ROTATIONAL SPEED SPIN-DOWN AND UNWRAPPING OF VARIOUS SIZE SYMMETRICALCRYOGENIC HELIUM BUBBLES AROUND DEWAR WELL IN MICROGRAVITY

Time dependent animation of doughnut-shape spinning bubble with variou s sizes wrapping around the dewar well at an equilibrium rotating spee d, which is spin-down to certain rotation speed is numerically studied and simulated. Time dependent deformation of a full wrapping bubble a round the rotating dewar well with and without unwrapping during the p rocess of spin-down motion are investigated. Critical rotating speed f or bubble to unwrap concerns the possibility of creating the problems of asymmetry in the imbalance liquid-vapor distribution due to sloshin g dynamics perturbations in the liquid-vapor interface. Some similarit y parameters are considered for how to promote the rotating dewar of b ubble without unwrapping around the dewar well during the spin-down mo tion. Examples are given to illustrate the problems for dewar with var ious liquid-fill levels. Results show that the degree to assure the bu bble without unwrapping around the rotating dewar well increases with increasing of the rotating speed, Weber number, and also the size of t he bubble.