Simulation and Experimental Study on Wastewater Degradation Based on Hydrodynamic Cavitation Impinging Stream

Hydrodynamic cavitation is a highly effective advanced oxidation process; however, in some cases, the use of a single hydrodynamic cavitation device may not be optimal for achieving maximum wastewater treatment efficiency. To enhance the operational efficiency of the hydrodynamic cavitation device, a novel hydrodynamic cavitation impinging stream (HCIS) reactor is proposed based on high heat and mass transfer efficiency characteristics of hydrodynamic cavitation. Based on the multiphase flow Mixture model, standard k-e turbulence model, and Schnerr-Sauer cavitation model, this study investigates the impact of inlet pressure and impinging distance on flow field characteristics and cavitation features in both the HCIS reactor and impinging zone. Furthermore, optimization of impinging parameters is carried out. The simulation results indicate that when the inlet pressure is 1.4 MPa and the impinging distance is 40 mm, there is an increase in turbulent kinetic energy within the impingement zone, resulting in a gradual rise in relative velocity on both sides of the jet. This leads to enhanced extrusion and shearing at the impact surface, ultimately resulting in high cavitation intensity. The optimized HCIS reactor and a single hydrodynamic cavitation device were compared for the degradation of Rhodamine B dye wastewater under optimal conditions, simultaneously. The results indicate that the HCIS reactor exhibits a degradation rate for wastewater treatment approximately 3.88 times higher than that of a single hydrodynamic cavitation device under optimal parameters. The strengthening index (SI) of the HCIS reactor is 2.54, and its degradation rate constant is 7.68×10⁻³ min⁻¹. Under identical conditions, the HCIS reactor can achieve superior wastewater degradation rates and cavitation yields at lower costs.