Instabilities of swirling liquid film in cylindrical chamber

A high-fidelity numerical exploration is carried out for the stability of a gradually thickened swirling liquid film on the inner wall of a cylindrical chamber. A comprehensive mathematical method is developed to extract spatially evolving instabilities. By examining the time averaged flow field and the characteristics of instability waves, two dominant instabilities (i.e., centrifugal and shear instabilities) are identified, and the interaction and competition between the two instabilities are discovered. The wave behaviors are primarily determined by the combination of flow and geometric factors: the liquid film thickness, profiles of the axial and azimuthal velocities, thickness of the boundary layer on inner wall surface, and curvature of the solid wall. As flow travels downstream, viscus dissipation makes the film thickness increase and the velocity profiles in the film change, which then trigger the transition of dominant wave types from one to the other. A unified theory for the onset and transition of instabilities of a swirling liquid film is established based on a comprehensive analysis of the flow characteristics over a wide range of operating parameters.