Multiscale dynamics in cryogenic cavitating flows: A coupled thermodynamic-population balance model and mechanism analysis

This study presents a novel cryogenic cavitation prediction framework that integrates bubble coalescence-breakup dynamics with a thermodynamically enhanced mass transfer model using a population balance model (PBM) approach. Validated against Hord's experiments, the developed PBM-Modified Zwart–Gerber–Belamri (PMZGB) model demonstrates 28% higher predictive accuracy than the conventional Zwart–Gerber–Belamri (ZGB) model, achieving a 19% relative error in cavitation length prediction while precisely resolving interfacial pressure-temperature distributions. Multiscale analysis reveals dual cavitation mechanisms: millimeter-scale cavity shedding is governed by low-frequency pressure pulsations (dominant mode at 499.57 Hz), whereas micrometer-scale bubble collapse is modulated by high-frequency dynamics (>1060.67 Hz). Characteristic bimodal bubble size distributions emerge, with micrometer-scale bubbles (0.001–0.5 mm) constituting over 50% of the population. Thermodynamic feedback through bubble coalescence and breakup emerges as a critical regulator of cavitation intensity, while millimeter-scale cavities (>3 mm) display pressure-dependent cyclic growth-decay patterns that dominate low-frequency pressure instabilities. The study elucidates how the dynamic equilibrium between coalescence and breakup mechanisms intrinsically controls cavitation cycles under varying flow conditions. Furthermore, the identified regulatory mechanisms involving vapor volume fraction (αv) and turbulent dissipation rate (ε) provide new insights for cavitation suppression strategies in cryogenic fluid machinery.