Direct numerical simulation of the near-field dynamics of annular gas-liquid two-phase jets

Abstract

Direct numerical simulation has been used to examine the near-field dynamics of annular gas-liquid two-phase jets. Based on an Eulerian approach with mixed fluid treatment, combined with an adapted volume of fluid method and a continuum surface force model, a mathematical formulation for the flow system is presented. The swirl introduced at the jet nozzle exit is based on analytical inflow conditions. Highly accurate numerical methods have been utilized for the solution of the compressible, unsteady, Navier-Stokes equations. Two computational cases of gas-liquid two-phase jets including swirling and nonswirling cases have been performed to investigate the effects of swirl on the flow field. In both cases the flow is more vortical at the downstream locations. The swirling motion enhances both the flow instability resulting in a larger liquid spatial dispersion and the mixing resulting in a more homogeneous flow field with more evenly distributed vorticity at the downstream locations. In the annular nonswirling case, a geometrical recirculation zone adjacent to the jet nozzle exit was observed. It was identified that the swirling motion is responsible for the development of a central recirculation zone, and the geometrical recirculation zone can be overwhelmed by the central recirculation zone leading to the presence of the central recirculation region only in the swirling gas-liquid case. Results from a swirling gas jet simulation were also included to examine the effect of the liquid sheet on the flow physics. The swirling gas jet developed a central recirculation region, but it did not develop a precessing vortex core as the swirling gas-liquid two-phase jet. The results indicate that a precessing vortex core can exist at relatively low swirl numbers in the gas-liquid two-phase flow. It was established that the liquid greatly affects the precession and the swirl number alone is an insufficient criterion for the development of a precessing vortex core.

Impact of Surrounding Gas Density on the Turbulent Liquid Jet

“…After that, Xiao et al [34] resolved the jet flow approach without the flow inside the nozzle. On the other hand, the evaluation of the in-nozzle swirl effect on the flow field of annular gas-liquid jets was studied by Siamas et al [35] using detailed VOF simulations. They reported that central recirculation region was developed as a result of the swirling motion.…”

Impact of the jet velocity on the turbulent liquid jet

“…Xiao et al [34] simulated the jet flow approach without the flow inside the nozzle. On the other hand, the evaluation of the in-nozzle swirl effect on the flow field of annular gas-liquid jets was studied by Siamas et al [35] using detailed VOF simulations. They reported that central recirculation region was developed as a result of the swirling motion.…”

Numerical study on pre-film atomization mechanism and characteristics by a coaxial swirl injector

“…Li and Soteriou 19 numerically investigated the atomization characteristics in a practical swirling flow and qualitatively demonstrated the validity and feasibility of the coupled LS and VOF approach through experimental results. As demonstrated by Siamas et al., 20 many of the existing studies on annular swirling liquid jets focused on experimental visualizations and simplified physical models, which were insufficient to reveal the details of complex liquid breakup and atomization in a two-phase environment.…”