Numerical and experimental investigations on the breakup of particle laden liquid jets in the centrifugal field

Abstract

The breakup of a particle laden viscous liquid jet, emitted from a cylindrical nozzle in a rotating cup and thus elongated by centrifugal force is studied by means of perturbation theory and experiments. In perturbation theory the flow of the jet is decomposed into a steady state motion and the transient motion of the small perturbations visible by the oscillation of the jet radius, which leads to breakup. The steady state equations of motion providing the contour as well as the trajectory of the unperturbed jet are derived by balances of forces and mass. The influence of the surrounding gas atmosphere is considered by a drag coefficient which is derived by means of computational fluid dynamics. The transient motion of the perturbations is studied by means of linear stability analysis. The equations of motion for the particle laden liquid jet are based on balances of mass and impulse in the Eulerian formulation. Hence each phase is treated as a continuum. The pressure oscillation in the surrounding gas is considered by treating the gas motion as potential flow. Both, temporal and spatial stability analysis is implied. Jet stability is also investigated experimentally. The curvature, breakup length and the resulting drops are analyzed using shadow imaging. The experimental findings are compared to the numerical model.