Microbubble generator excited by fluidic oscillator's third harmonic frequency

•Oscillator and aerator form an integral bubble-generator unit.•Unit is excited by oscillator's 3rd harmonic frequency.•The very high frequency is the main gained advantage. Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation.