Friday, February 21, 2014 at 3:30pm
Liquid-gas systems often display a range of complex flow dynamics including instabilities, turbulence, and dramatic changes of the phase-interface topology. Liquid atomization is one of the most striking examples of this fact. Due to its extreme complexity and non-linearity, a comprehensive and predictive theory of turbulent liquid atomization has yet to be proposed. This, in turns, explains the paucity of engineering models for liquid atomization, a critical process in liquid-fueled combustion devices. In this talk, we explore the use of large-scale first-principle simulations to capture the fundamental physics of liquid atomization.
Several properties have proven to be highly desirable when designing numerical methods for simulating liquid-gas flows. When tracking the liquid-gas interface, ensuring discrete conservation of the volume in both phases is often critical. In addition, the capability of automatically handling topology changes can be beneficial, especially for atomizing flows. In order to calculate the surface tension force, it is necessary to estimate the interfacial curvature with good accuracy. Most existing multiphase methods verify some but not all of these requirements. We will discuss the development of a novel framework based on transporting moments of the liquid distribution function that addresses each point carefully. The coupling of this new method for phase-interface transport with a Navier-Stokes solver will also be discussed, with emphasis on handling of discontinuous variables such as pressure and fluid momentum.
This recently advanced methodology will then be employed in the detailed study of various liquid-gas flows of increasing complexity. In particular, a turbulent liquid jet in a cross-flow will be presented, with comparison of droplet sizes to experimental measurements, as well as preliminary work on an electrohydrodynamic liquid-gas flow.