Effect of Throat Cross-Sectional Aspect Ratio on the Cavitation Characteristics of Flat-Slot Cavitating Water-Jet Nozzles: A Flow-Field Design Basis for Flake Graphite Exfoliation

Flat-slot nozzles with noncircular throat cross-sections have potential applications in liquid-phase exfoliation of flake graphite. This study investigated the effect of throat aspect ratio (AR) on cavitation using the Mixture multiphase, SST k-ω turbulence, and Zwart–Gerber–Belamri cavitation models for one circular nozzle (AR = 1) and four flat-slot nozzles (AR = 3, 5, 7, and 9). High-speed imaging compared macroscopic cavitation-cloud morphologies and their variations. At a constant throat cross-sectional area, relative differences in peak time-averaged centerline velocity were below 1%, indicating limited AR effects on peak jet velocity. However, AR markedly altered the near-exit velocity field and cavitation-cloud distribution. Increasing AR enhanced lateral spreading of the high-speed core and accelerated downstream centerline velocity decay. The global maximum of the time-averaged vapor volume fraction field changed only slightly, decreasing initially and then increasing. For flat-slot nozzles, peak time-averaged centerline vapor volume fraction increased markedly from 39.26% (AR = 3) to 77.84% (AR = 9), a 98.27% relative increase. Cavitation progressively extended from localized near-wall regions toward the jet center. High-speed imaging showed cavitation-cloud morphologies and AR trends generally consistent with simulations. These findings clarify AR-induced cavitation redistribution and provide guidance for nozzle design in future flake graphite exfoliation studies.