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.

A Quantitative Study on the Decreased Diameter of Bubbles Generated from a Submerged Orifice with an Oscillatory Air Supply

“…Replacing a steady air supply with an oscillatory air supply could drive the initial bubble detachment at an earlier stage and thus decrease bubble diameter to some extent. However, the bubble diameter reduction is mainly determined by coalescence depression while increasing the switching frequency, consistent with the report by Tesař …”

“…However, the bubble diameter reduction is mainly determined by coalescence depression while increasing the switching frequency, consistent with the report by Tesar. 31 3.2.2. Bubble Formation under Different On/Off Time Ratios.…”

Editorial for the Special Issue on “Fluidic Oscillators—Devices and Applications”

“…The range of potential applications for fluidic oscillators is rounded off by the topic of air bubble generation, as discussed by Tesař [25]. Creating air bubbles with defined diameters is of high interest not only for scientific observations but also for several practical applications such as waste water treatment or oxygen supply at fish farms.…”

Microbubble generation driven by the oscillation in a self‐excited fluidic oscillator

“…In order to prevent these conjunctions, Zimmerman et al 8 and Tesař 9 carried out a seminal research by oscillating the fluid flow upstream from an aerator. They started a whole range of new applications of the microbubbles generated by oscillating air flow into water in the reactor.…”