Stability of the fluid-fluid interphase in rotating systems subjected to different gravitational intensities

When an isothermal, constant volume, constant mass system containing two fluid phases is rotated in the absence of gravity, the lighter phase adopts a position on the axis of rotation. As the rate of rotation increases, the phase becomes elongated along its axis. If a gravitational field is applied in a direction perpendicular to the axis of rotation, depending on the field intensity, the rate of rotation and the system parameters, the lighter phase can become unstable and break into several smaller volumes. An experimental study of the stability of both the liquid-liquid and liquid-vapor phases of such a system was carried out at elevated, normal, and reduced gravitational intensities during parabolic flights in a KC-135 aircraft. It was found that for a given set of system parameters and gravitational intensity, there is a limiting value of the rotation rate at which the interphase will remain stable. Conversely, for a given rotation rate, there is a limiting gravitational intensity at which the interphase remains stable. From a simple force balance and ideal fluid theory, the experimental results are found to indicate that the difference in velocity of the fluid between the top and bottom of the lighter phase at breakup is a constant for a given system.