Insight into the dynamics of internal and external flow fields of the pressure swirl nozzle

In this paper, the temporal and time-averaged behaviors of the internal and external flow fields of the pressure swirl nozzle are investigated through a three-dimensional, two-phase flow, large-eddy simulation. The volume-of-fluid method is used to simulate the air and liquid regions using the commercial package STAR-CCM+. The constructed polyhedral grids are refined locally, and their quality is assessed through the M-criterion and the slope of the fast-Fourier-transformed time-resolved probes. For the detailed analysis, internal and external grids are defined, and the data points are extracted. MATLAB is then used for postprocessing purposes. The frequencies obtained from the vortex core tracking inside the nozzle are then spatially depicted using proper orthogonal decomposition for both internal and external flow fields. Unique structures are identified and explained in detail, where each is linked to a particular frequency. The up-stream vortex core inside the swirl chamber is observed to relocate perpendicular to the nozzle axis at a distinct frequency. Additionally, the spray behavior and its corresponding frequencies are found to be related to the structures inside the nozzle throat.