Numerical prediction of added mass and damping for a cylinder oscillating in confined incompressible gas–liquid two-phase mixture

This paper is concerned with the numerical analysis of the added mass and damping of a circular cylinder, which oscillates in an air–water bubbly mixture enclosed by a concentric shell. The mixture is assumed to be incompressible. This is because the oscillation frequency of the cylinder is low in this study, and accordingly the pressure change around the cylinder is not so large. An incompressible two-fluid model is solved by the finite element method, proposed by the author in a prior paper, to calculate the bubbly flow around the oscillating cylinder. The analysis reveals the effects of the diameter ratio of the cylinder to the shell, the air volumetric fraction and the bubble diameter. It also clarifies that the increase of damping ratio in the bubbly mixture is attributable to the phase lag of the drag force acting on the cylinder behind the cylinder displacement.