VISCOUS FILM FLOW IN THE STAGNATION REGION OF THE JET IMPINGING ON PLANAR SURFACE

A capillary jet of liquid impinges on a planar surface that is normall y oriented to the axis of the jet. The surface is initially covered wi th a thin uniform film of a viscous liquid. The impact and radial spre ading of the liquid from the jet cause the underlying viscous film to be removed from the surface. An approximate analysis predicts the thin ning rate of the film in the stagnation region of the jet. It uses the shear stress and pressure distribution of the classical Homann flow a s boundary conditions for an analytical solution of the Reynolds lubri cation equations in this underlying viscous film. A more exact analysi s modifies the Homann flow to account for the mobility of the liquid f ilm beneath the spreading jet and sheds light on the limitations of th e analytical lubrication analysis. Data presented are in excellent agr eement with the theory, subject only to the choice of a value for the hydrodynamic constant that appears in the Homann analysis.