A study of the dynamics of a single cavitation bubble is fundamental for understanding a wide range of applications in science and engineering. Underwater electrical discharge is a widely used method for generating cavitation bubbles to study their inception, subsequent dynamics, and collapse. In this work, an existing underwater low-voltage discharge circuit for generating cavitation bubbles is improved further to get a wider range of maximum bubble radius. In this novel electric circuit design, the operating voltage can be varied (up to 420 V in steps of 60 V) by connecting a network of capacitors in different series-parallel combinations with the help of relay-based control. Therefore, this device can generate oscillating cavitation bubbles up to a maximum radius of 14 mm by adjusting the available discharge energy. A voltage sensor circuit is included in this design to measure the drop in voltage during the sparking event, and a correlation between the delivered energy and the potential energy of the bubble is established. The dependence of bubble radius on circuit resistance, electrode resistance, and electrode material is studied for the entire voltage range. A suitably rated semiconductor field effect transistor is used as a switch that enables the generation of bubbles of a consistent maximum radius and ensures the repeatability of the experiment. A high-speed imaging system is used to estimate the bubble radius and nucleation period, which are compared with the existing theoretical models based on empty cavity collapse. Results show that delaying the oxidation of electrodes with a protective layer influences the collapse phase and the average pressure inside the spark-generated bubble.
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Sci Rep
January 2025
Udmurt Federal Research Center of the Ural Branch of RAS, Baramzina str. 34, Izhevsk, 426067, Russia.
Ultrasound can improve the quality of finished products by reducing porosity and enhancing microstructure in selective laser melting, directed energy deposition, and laser beam welding. This study evaluates the efficiency of ultrasound produced by a pulsed laser via the optoacoustic effect. A quantitative model of collapse of vapor-gas bubbles has been developed under the conditions of ultrasonic treatment at near resonance frequencies.
View Article and Find Full Text PDFACS Mater Au
January 2025
Department of Biomedical Engineering, Tel Aviv University, Tel Aviv 6997801, Israel.
Gas bubbles, commonly used in medical ultrasound (US), witness advancements with nanobubbles (NB), providing improved capabilities over microbubbles (MB). NBs offer enhanced penetration into capillaries and the ability to extravasate into tumors following systemic injection, alongside prolonged circulation and persistent acoustic contrast. Low-frequency insonation (<1 MHz) with NBs holds great potential in inducing significant bioeffects, making the monitoring of their acoustic response critical to achieving therapeutic goals.
View Article and Find Full Text PDFMicromachines (Basel)
December 2024
Department of Mechanical Engineering, The University of Memphis, Memphis, TN 38152, USA.
Microbubbles, acting as cavitation nuclei, undergo cycles of expansion, contraction, and collapse. This collapse generates shockwaves, alters local shear forces, and increases local temperature. Cavitation causes severe changes in pressure and temperature, resulting in surface erosion.
View Article and Find Full Text PDFUltrason Sonochem
January 2025
School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China; MOE Key Laboratory of Cryogenic Technology and Equipment, Xi'an Jiaotong University, Xi'an 710049, China.
Cavitation plays a crucial role in the reliability of components in refrigeration systems. The properties of refrigerants change significantly with temperature, thereby amplifying the impact of thermodynamic effects. This study, based on the Large Eddy Simulation (LES) method and the Schnerr-Sauer (S-S) cavitation model, investigates the transient cavitating flow characteristics of the R134a refrigerant in a Venturi tube (VT).
View Article and Find Full Text PDFUltrason Sonochem
January 2025
School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350, China; Tianjin Key Laboratory of Chemical process safety and equipment technology, Tianjin 300350, China. Electronic address:
Ultrasonic reactors, widely applied in process intensification, face limitations in their industrial application due to a lack of theoretical support for their structural design and optimization, particularly concerning the uniformity of the cavitation zone. Addressing this gap, our study introduces a novel approach to design a multi-frequency octagonal ultrasonic reactor of capacity 9.5 L through numerical simulation and spectrum analysis.
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