Suppression effects of non-condensable gas on cavitation in centrifugal pumps: Numerical insight from a modified volume of fluid-cavitation model

Cavitation in centrifugal pumps is affected by non-condensable gas (NCG), thus influencing hydraulic performance and operational stability due to gas–liquid–vapor multiphase interactions. Traditional simulations are difficult to accurately capture the dynamic gas–liquid–vapor interfaces under gas-entrained conditions, and there are limited studies that address the influence of NCG on cavitation—especially concerning energy dissipation mechanisms and phase interface evolution. This study presents a numerical framework called modified Volume of Fluid (VOF)-cavitation model that integrates an enhanced three-phase VOF model with a improved Zwart–Gerber–Belamri cavitation model. Simulations examine centrifugal pump cavitation at 900 r/min with inlet gas volume fractions (IGVFs) of 0%, 0.18%, 0.76%, and 2.64%, incorporating energy gradient theory, entropy production analysis, and Omega vortex identification to quantify flow instabilities. The results show that the modified VOF-cavitation model accurately resolves discontinuous phase interfaces (gas–liquid and vapor–liquid), validated against experimental bubble dynamics. The optimal IGVF (0.76%) enhances pump head and efficiency by suppressing vapor cavity growth through gas-cushion effects and reducing the vapor volume fraction. An increase in IGVF shifts the dominant vapor fluctuation frequencies downward (impeller: from 45 to 30 Hz and volute: from 21 to 11.15 Hz). Gas entrainment causes a shift in entropy production dominance from direct dissipation to turbulent dissipation, increasing energy losses by 15%–20%. Gas entrainment critically modulates cavitation dynamics, and this framework based on the modified VOF-cavitation model facilitates precise multiphase prediction for pump optimization.