Numerical Simulations of Swirling Water Jet Atomization: A Mesh Convergence Study

We report on numerical simulations of a swirling water jet flowing out of a nozzle into a still air atmosphere at normal conditions. Primary jet breakup and atomization were studied with an emphasis on the effect of grid resolution on the results. Jet inlet diameter D was set to 0.8 mm, a bulk velocity was set to 7.6 m/s (Re=6100, Wel=650), and the swirl rate was set to S=0.3. The near region of the jet (up to x/D=16) was studied. The results were obtained for four different grid resolutions with the smallest cell size of 6 μm. It is shown that the use of an adaptive mesh refinement procedure for interface tracking allows us to get to convergent results in terms of both droplets volume and surface area distributions, while the total number of droplets changes with the increased grid refinement level. This phenomenon may be attributed to the formation of small (grid-cell sized) droplets due to numerically-triggered instabilities at the gas-liquid interface.