DIRECT NUMERICAL SIMULATION OF INTERFACE BREAKUP AND ATOMISATION

Numerical studies of the breakup of sheared liquid−gas interfaces subject to the Kelvin−Helmholtz instability are described. The incompressible Navier−Stokes equations are solved on a Marker And Cell (MAC) staggered finite-difference grid together with a projection algorithm for the pressure. For the kinematics of the interface a second order scheme is used. Surface tension is modeled by a scheme that conserves momentum exactly in the discretized equations. This enables to follow droplet formation and ejection away from the liquid layer. Droplet ejection occurs at much higher Weber and Reynolds numbers than predicted by linear theory. The precise mechanism involves formation and detachment of a boundary layer.