Oscillating microbubbly flows generated by a fluidic oscillator: Flow behavior and mass transfer characteristics

Abstract

In this study, a Coanda-swept fluidic oscillator is used to generate oscillating microbubbly flows. Flow behavior measurements show that the generated microbubbly flows have periodic sweep characteristics. Massive microbubbles are generated by shear-off-induced breakup, dynamic erosion breakup, and wall-fluid-shear-induced breakup within the fluidic oscillator. Mass transfer measurements show that the generated microbubbly flows have a higher interfacial area (a) and volumetric liquid-side mass transfer coefficients (k_L) than the other comparison groups. Furthermore, the energy efficiency is assessed in terms of k_L per energy consumption (η) and energy consumption per a (ξ). For the fluidic oscillator group, the highest k_La is 0.089 s⁻¹, corresponding to (η = 0.63 m³/(kW·s), ξ = 2.6 J/m², a = 785 m²/m³). Although it has been reported that higher k_La is typically associated with lower energy efficiency, the results indicate that the fluidic oscillator is a promising microbubble generator.