Dissolved air effects on three-phase hydrodynamic cavitation in large scale Venturi- Experimental/numerical analysis

Hydrodynamic cavitation (HC) in the Venturi nozzle, apart from the harmful influence on the devices, can be used to improve a range of industrial processes, such as biofuel generation, emulsion preparation, and wastewater treatment. The present investigation deals with the influence of dissolved air in Venturi cavitating flow based on numerical and experimental approaches. The experimental campaigns have been done in a closed-loop water tunnel equipped with a Venturi test section. The post-processing techniques such as Fast Fourier Transform (FFT), Power Spectral Density (PSD), temporal/spatial Grey Level distribution and mean value grey level distribution are employed to analyse the experimental observations and measurement. The URANS numerical method is modified based on the Density Corrected-Based Model (DCM) to be more adaptable for flows with high differences in density. The results approve the remarkable effect of dissolved air on the configuration of the cavity, its evolution process, and transient/averaged characteristics. It is observed that the incipient point and ratio of sheet cavity length to cloud cavity length are changed. Furthermore, the flow velocity inside of the sheet and cloud cavities is different; as well as, the higher content of dissolved air leads to slower flow velocity inside the cloud cavity. In addition, the shedding frequency is significantly reduced in case of higher level of air content.