Fluid Dynamics of Viscous Liquid Sheets

摘要

In this paper the fluid dynamics of thin viscous liquid sheets isinvestigated. The process engineering context comes from the application of such sheets in curtain coating devices. In the first part of the paper, the propagation of disturbance signals in a uniformly thin viscous liquid sheet of infinite extent which is in contact with a passive ambient medium is investigated. The disturbances considered are induced by local external pressure perturbations moving on the sheet interfaces. The tool of analysis is the Fourier-Laplace transform of the linearized perturbation equations, and the inverse Fourier-Laplace transform for the numerical reconstruction of the amplitude of the interface deflections. Symmetric (varicose) and antisymmetric (sinuous) disturbances are investigated in the long time limit by numerical signal evaluation. The exact disturbance responses are compared with their longwave approximations. In the second part of the paper, the dynamics of a rim on a thin liquid sheet is investigated. Such rims occur when the sheet ruptures. The results provide insight into the role of viscosity in the dynamics of edge retraction and its implications on the break-up of a liquid curtain due to a free rim.