Long-term effect of nanobubbles generated by turbulent flow through diamond-pattern notches on liquid properties

Abstract

In this work, we generated submicron bubbles (nanobubbles) using nanobubble generating nozzles (NBGNs) with diamond pattern notches. NBGNs are of great interest because they can generate nanobubbles within vortices at high flow rates without any external energy supply. However, the mechanism that generates nanobubbles has not been fully understood due to the lack of characterization of nanobubbles and quantitative evaluation of nanobubble effects. Here, we revealed the presence of nanobubbles generated by NBGNs in turbulent flow using a high-speed camera with a high magnification lens and found the optimal flow conditions to generate nanobubbles. In addition, using a dynamic light scattering system, we confirmed the size distribution of nanobubbles. Furthermore, based on the type and material of NBGNs, the effect of nanobubbles was experimentally investigated. As a result, we found that the working fluid with nanobubbles produced by the NBGNs had low viscosity and high antibacterial properties due to the effect of nanobubbles. Moreover, the nanobubble effect was persisted or intensified for at least one day. As a result, we showed that NBGNs generated nanobubbles with a long-term effect on bacterial viability and liquid viscosity.