Biomedical Engineering Reference
In-Depth Information
Figure 1. Sequence of events for collision and attachment of a bubble rising in an aqueous solution
onto a large planar solid surface placed horizontally to gravity.
dissipating the kinetic energy into the potential energy of the bubble surface defor-
mation. The bubble-surface collision may undergo sequential oscillatory motion
until the momentum of the bubble rise is sufficiently lost. Finally, the bubble rests
at the surface to allow for the liquid drainage and rupture. The bubble oscillatory
motion and the deformation of the bubble surface due to collision and capillarity and
intermolecular interactions are described in Section C. Interfacial forces due to in-
termolecular interactions are specifically described in Section D. The film drainage
and rupture are described in Section E. After the film rupture, a three-phase contact
(TPC) area is formed, expands and relaxes. The dynamics of the TPC spreading and
relaxation is described in Section F. A summary and conclusions of the review are
giveninSectionG.
B. Motion of Bubbles Before Interacting with the Surface
As briefly highlighted in the Introduction, collision and attachment of a rising bub-
ble and a solid surface can be effectively described by splitting the interaction zone
into two small zones which are dominantly governed by the (long-range) hydro-
dynamic forces or (short-range) interfacial forces. In the long-range hydrodynamic
zone, which is far from the solid surface, the bubble is considered to freely rise in
the aqueous solution. At steady state, the bubble motion is governed by the bal-
ance between the fluid resistance and gravitational forces which leads to various
drag laws and predictions for the bubble rise velocity. Summarised below are many
important aspects of physiochemical hydrodynamics, interfacial rheology and the
terminal velocity of bubble rise.
1. Physiochemical Hydrodynamics and Interfacial Rheology of Bubble Rise
Bubble rise velocity is a complicated function of the bubble geometry, the physical
properties of the medium and the dynamic physicochemical properties of the gas-
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