Control-volume study of flow field in a two-phase cyclonic separator in microgravity

The separation of two-phase flow is essential for many fluid systems in microgravity environments. The passive cyclonic separator is a prominent technology for this task. In the absence of gravity, the separators can operate in different parametric ranges than in normal gravity. The objective of the present investigation is to better understand the fluid physics involved in two-phase flow separation in microgravity by deriving the basic scaling laws for various important parameters. Combined approaches of control-volume analysis and numerical simulations are used to construct a system of equations that can accurately predict the gas core size under various conditions. The predictions are found to be in good agreement with the experimental data, both for pure liquid injection and two-phase flow injection cases. The control-volume equations are modified to include capillary effects and predict the critical condition for the collapse of the liquid layer in microgravity as the surface tension overcomes the centrifugal acceleration at the interface. It is shown that the results of the control-volume analysis can also be used to construct the operational map and to study the separation of a single bubble in microgravity.