Dynamics and instability of free interface flows: applications to industrial processes


Monday, 12 December, 2016 - 18:15

Speaker: Dr Michele Girfoglio, University of Naples “Federico II"

Room: A-005, SISSA Campus, Via Bonomea 265, Trieste
Free surface flows occur frequently in many industrial processes such as casting or injection. Within the framework of complex flows with liquid-gas free surfaces, the control of the break up of liquid jets (both plane and annular) plays a key role for the final quality of the product. Vertical liquid curtains are often used in technological processes, classical examples being coating technology and papermaking. In this talk, the unsteady global dynamics of a gravitational liquid sheet interacting with a one-sided adjacent air enclosure (commonly referred to as nappe oscillation configuration) will be addressed, under the assumptions of potential flow and presence of surface tension effects. It will be shown that the unsteady dynamics can be described by means of a typical integro-differential equation of hyperbolic type, exhibiting two distinct characteristic curves. An interesting re-formulation of the nappe global behavior as a driven damped spring-mass oscillator will be addressed. A relevant procedure, which has been employed in order to remove the singularity exhibited by the integro-differential operator for Weber number less than unit, will be presented. The investigation has been carried out by means of a modal (i.e., time asymptotic) linear approach, which is corroborated by direct numerical simulations of the governing equation. In the final part of the seminar it will be briefly illustrated the numerical investigation of a slag-steel interface surface in a continuous casting process.