Spray formation under the effect of micro scale cavitation and its biomedical applications

Official URL: https://risc01.sabanciuniv.edu/record=b2553763 _(Table of contents)

Hydrodynamic cavitation is characterized by the formation of bubbles inside the flow due to local reduction of pressure below the vapor saturation pressure, growth, and violent collapse of bubbles leading to a huge amount of released energy. This energy is extensively studied and implemented in different fields, namely, surface cleaning, heat transfer enhancement, food industry, wastewater treatment, and chemical reactions. It is experimentally proven that hydrodynamic cavitation inside the nozzle enhances the atomization characteristics of the emerging spray. In this study, cavitating flows inside a transparent cylindrical nozzle with an inner diameter of 0.9 mm were visualized, and the effect of cavitation on atomization characteristics of emerging sprays was investigated by processing the captured images using a developed in-house code, the effect of cavitation on spray characteristics was investigated. By changing the working fluid from water to poly(vinyl alcohol) microbubbles (PVA MBs) suspension and roughening the inner wall of the nozzle, we were able to reduce the required injection pressure for cavitation inception. Moreover, the atomization characteristics of the emerging jet was enhanced considerably. A cystoscope, which houses a cavitation probe to exploit the energy released during cavitation bubble collapse for the treatment of urinary stones and cancer tissues, was designed and fabricated. The developed biomedical device utilizes a novel control system to locate the precise region and apply the cavitating flow. In vitro experiments showed that the device possesses a high capability of locating and ablating cancer tissues