Stability Aspects of Gas Bubbles in Slug Flow Available to Purchase

In a microgravity gas-liquid flow, the greater importance of surface tension relative to body forces considerably enlarges the region of parameter space in which slug flow is encountered. This paper describes numerical simulations which focus on two aspects of the stability of this type of flow. The first one is the stability of a periodic system of axisymmetric bubbles as their mutual distance is reduced. It is found that, below a certain minimum distance dependent on the parameters of the problem, consecutive bubbles tend to merge thus triggering a transition to annular flow. The second problem concerns the stability of axisymmetric flow with respect to non-axisymmetric disturbances. To study this problem, a linear stability analysis is carried out by means of a domain perturbation approach based on a numerically computed axisymmetric base state. The perturbation equations are solved numerically on the assumption of an exponential time dependence of the perturbation quantities. The numerical method used for both problems is based on a fixed-grid, front-tracking method in which the interface is tracked by means of Lagrangian marker points.