Interface instability mechanism of an annular viscous liquid sheet exposed to axially moving inner and outer gas

Abstract

The interface instability mechanism of an annular viscous liquid sheet exposed to axially moving inner and outer gas is investigated. Sheet instability and breakup have been investigated using a nonlinear spatial instability analysis. A perturbation expansion method is used with the initial amplitude of the disturbance as the perturbation parameter. The evolution of the two gas–liquid interfaces is tracked until the sheet breaks up and the breakup length is determined. The model is validated by comparison with available experimental data. To investigate the interface instability mechanism of an annular viscous liquid sheet, the effects of velocity difference between gas and liquid, annular curvature on the annular sheet instability have been studied. The results show that both first-order and second-order maximum disturbance growth rates increase with increase in velocity difference between gas and liquid, and annular liquid sheet curvature. Also, with increasing velocity difference between gas and liquid, large interface deformations occur and the breakup length of the annular viscous liquid sheet becomes shorter. The shear effect difference between the outer and inner sides of the annular liquid sheet is the source of instability.