Researchers from the Laboratory for Hydraulic Machines (LVTS) investigated how both dissolved and undissolved gases influence cavitation, revealing an often-overlooked aspect of liquid quality. The results of the study were published in the journal Ultrasonics Sonochemistry (IF=9.7).
Cavitation plays a key role in many technologies, from ultrasonic cleaning to chemical processing, yet it can behave unpredictably due to liquid quality. This study shows that cavitation is shaped not only by dissolved gas, but also by tiny, undissolved gas bubbles, helping to improve the repeatability and efficiency of cavitation-based systems in industry and research.
The gas content of a liquid is a fundamental indicator of liquid quality and a key factor influencing cavitation behaviour. Despite its importance, gas-related effects are frequently overlooked in both cavitation research and industrial applications, where liquids are often assumed to be comparable. In practice, gas content is typically assessed only through dissolved gas measurements using sensors, while undissolved gas bubbles present in the liquid are often overlooked. This study highlights the limitations of relying solely on dissolved gas measurements in cavitation studies.
By comparing liquids with different dissolved gas levels, as well as liquids with identical dissolved gas levels but different concentrations of tiny air bubbles (<200 µm), this work demonstrates that gas content strongly affects both cavitation inception and its developed state. High-speed observations and acoustic measurements show that in undersaturated liquids, cavitation can initiate from a single nucleus and generate stronger collapse-related acoustic noise. In contrast, the presence of undissolved gas bubbles promotes earlier and more organised cavitation structures while reducing acoustic intensity. These effects disappear once the bubbles are removed, demonstrating that dissolved gas alone cannot fully represent gas-related influences on cavitation. The study therefore suggests that future cavitation research and industrial applications should consider both dissolved and undissolved gas content to achieve more reliable control and understanding of cavitation.