Cavitation characteristics and degradation capability of an annular slit rotating hydraulic cavitation generator

A groundbreaking and remarkably efficient strategy can be expected to be formulated for the mitigation of organic wastewater in recent years. In this study, an elaborate and all-encompassing investigation was implemented to determine the intricate mechanism behind the cavitation characteristics of a rotary hydraulic cavitation apparatus. A series of techniques were seamlessly integrated with cutting-edge and sophisticated high-speed photography along with precision-oriented pressure fluctuation testing. A systematic analysis aimed at the innermost cavitation flow dynamics within the confines of a circular narrow slit configuration. There was the very heart of a rotary hydraulic cavitation generator. This comprehensive experimental inquiry yielded an invaluable reservoir of insights across an array of dynamically varying flow conditions. An additional layer of depth was added to select methylene blue as the designated degradation reagent, thereby enabling an astute and comprehensive evaluation of the cavitation device's remarkable proficiency in breaking down and degrading recalcitrant organic substrates. The empirical revelations served to unveil a rich tapestry of cavitation manifestations, each weaving a unique narrative within the apparatus's intricate landscape. These manifestations encompassed the inception of cavitation at the forefront of the circular narrow slit structure, the subsequent propagation of cavitation within the confined precincts of blind holes, the remarkable emergence of cavitation formations at the trailing edge of these very same blind holes, and the subsequent ripple effect culminating in cavitation events at the trailing edge of the circular narrow slit structure. Two prominent modes were highlighted in this diverse panorama: the cavitation occurrences within the confines of the restricted blind holes and the eloquent cavitation events materializing at the trailing edge of the circular narrow slit structure. Furthermore, the cavitation unfolding at the trailing edge of the circular narrow slit structure exhibited an intriguingly rhythmic and quasi-periodic sequence of events. A cyclic progression was characterized by expansion, detachment, and ultimate collapse. This mesmerizing cycle resonated with a temporal cadence hovering around the 1.78 ms mark, indicating the inherent dynamics. Subsequently, some fluctuations were captured in the form of discernible pressure at the outlet of the intricate volute casing. This compelling cavitation generator was the nucleus of this elaborate investigation. An unparalleled performance was achieved for the fluid conveyance over an expansive spectrum of dynamic flow conditions. The landscape of cavitation underwent a transformative journey: transitioning from the nascent phase of incipient cavitation to the captivating allure of the cloud cavitation phenomenon, as the flow rates surged and surged further still. The cloud cavitation shared the unfurling across the circumferential realm with a regal length approximating 26 mm and then coupled with a radial span of around 14 mm at the notable juncture of 36 m³/h flow rate. An intensification of cavitation dynamics was obtained for the further surge in the flow intensity at 37.5 m³/h brought forth. There was the distinctive "V"-shaped cavitation pattern in the leading edge of the narrow-slit structure with a captivating. There was an intricately woven tapestry that partially enveloped the confines of the revered blind holes. The enhanced intensity of cavitation shared profound repercussions. The amplitude was amplified for the blade passing frequencies. Consequently, there were amplified and richly textured broadband pressure fluctuations. Furthermore, the cavitation generator demonstrated an optimally calibrated capacity for the degradation of methylene blue under meticulously tuned flow and initial solution concentrations. The zenith of the degradation potential (a crescendo of sorts) was discerned at the distinguished crossroads of a 36 m³/h flow rate in the initial solution concentration with a precise 1.5 mg/L. The finding can provide a strong reference for agricultural organic wastewater treatment.