Abstract |
Flow Regimes Induced by Pulsating Gas
Bubbles in Living Tissues
B.Krasovitski, E.Kimmel (Agricultural
Engineering and Biomedical Engineering, Technion, Haifa, Israel)
e-mail:
agboris@tx.technion.ac.il
Gas
bubbles in living tissues, when subjected to therapeutic ultrasound (TUS), may
be found in relatively large cavities such as blood vessels, in intercellular
spaces and within cells. In the case of low intensity TUS, bubble close to a
rigid wall in relatively large cavity undergoes steady pulsations. Laplace
equation for potential flow is solved employing existing models for
microstreaming and rectified diffusion to yield the steady shear stress on the
surface. Significant values of localized shear are predicted when the distance
of the bubble from the surface is comparable to bubble size. For greater TUS
intensity, when bubble might collapse near a surface, we study bubble behavior
in confined space that simulates a tiny cavity such as intercellular space. A
numerical model is developed for a bubble in the middle of a liquid layer,
between two rigid, parallel walls. The solution ia based on boundary integral
method and consider surface tension effects. In some cases, the bubble divides
into two symmetrical bubbles that collapse while high velocity jets are
generated, aiming at the walls. The velocity of the jets strongly depends on
the surface tension. Two new parameters define under what conditions the
formation of jets is expected.
Section
: 5