Performance optimization of multistage orifice-Venturi cavitation reactors via integrated experimental and numerical investigation: Influence of perforation layout on cavitation efficiency and hydrodynamic stability

Hydrodynamic cavitation, due to its chemical-free operation, demonstrates remarkable potential for the treatment of industrial wastewaters and the degradation of recalcitrant organic contaminants. This study proposes a multistage cavitator that integrates orifice plates with a Venturi tube to achieve secondary relay-type cavitation, enhancing cavitation efficiency. A combination of experimental measurements and numerical simulations is employed to systematically investigate the performance of the proposed design. Numerical simulations using the Zwart–Gerber–Belamri cavitation model coupled with the shear-stress transport k–ω turbulence model are conducted for single-orifice, triple-orifice, and quintuple-orifice configurations. Results demonstrated that, compared to conventional Venturi tubes, the multistage hydrodynamic cavitator exhibits significantly improved cavitation intensity and expanded cavitation zones. The cavitation volume increases by 23%–48%, 33%–68%, and 38%–76% for single-orifice, triple-orifice, and quintuple-orifice configurations, respectively, indicating a strong positive correlation between orifice number and cavitation performance through the superposition of cavitation regions. The intensified secondary cavitation generates elevated turbulent kinetic energy zones, which amplify vibration levels and localized energy dissipation. Both experimental and numerical results reveal that cavitation cycles are substantially shortened in the multistage cavitator compared to conventional designs, with cycle duration further decreasing as the orifice number increases. Pressure pulsation spectra analysis indicated that the multistage cavitator covers full-frequency bands, with increasing high-frequency amplitude corresponding to higher orifice counts. Optimal performance is achieved with symmetrically distributed multiple orifices. However, increasing the number of orifices inevitably induces higher amplitude high-frequency vibrations and intensifies local energy dissipation.