Fluidic Oscillators Mediating Generation of Microbubbles (Survey)

Abstract

If a gas volume is distributed into many microbubbles of a sub-millimetre size, the total gas/liquid surface becomes very large. This increases overall heat and/or mass transport across the sum of surfaces. The paper discusses several applications in which the use of microbubbles increases efficiency of various processes, especially in wastewater treatment and in growing microorganisms such as algae, yeast, bacteria, or primitive fungi. The problem of microbubble generation by percolation in aerator is their coalescence into larger bubbles, whatever small are the pores in the aerator in which the microbubbles are generated. The solution of this size discrepancy question was found in agitating the gas flow by a fluidic oscillator prior to its injection through the aerator. The oscillator is a no-moving-part device, simple, inexpensive, resistant to external effects like acceleration or heat, and with long maintenance-free working life.