Particles in Flows

0476911 - ÚT 2018 RIV CH eng M - Monography Chapter
Tesař, Václav
Microbubbles: Properties, Mechanisms of Their Generation.
Particles in Flows. Basel: Birkhäuser Basel, 2017 - (Bodnár, T.; Galdi, G.; Nečasová, Š.), s. 453-519. ISBN 978-3-319-60281-3
R&D Projects: GA ČR GA13-23046S
Institutional support: RVO:61388998
Keywords : conjunction * fluidic oscillators * fluidics
OECD category: Fluids and plasma physics (including surface physics)

This chapter discusses microbubbles—small gas bubbles in liquid medium of diameter less than 1 mm. Although they were known to offer a number of advantages, until recently they could be generate only by energetically inefficient methods. New horizons became open by the discovery of generation by aerators provided with an oscillator in their gas supply. Chapter provides in particular an information about no-moving-part fluidic oscillators, recently already almost forgotten but now demonstrated to offer benefits like low manufacturing cost, reliability, long life and absence of maintenance. The empirical fact that small bubbles cannot be obtained simply by making small passages in the aerator is here explained by conjunction of several microbubbles. Because the velocity of bubble motion decreases with decreasing size, small microbubbles tend to dwell near the aerator exits. They then coalesce there into a much larger bubble (the trend supported by the latter possessing lower surface energy). The fact that the oscillator prevents this conjunction and thus keeps the microbubbles small has been explained by high-speed camera images which show the effect of oscillatory motions.
Permanent Link: http://hdl.handle.net/11104/0276810