Abstracts - KTH Mechanics

174
BUBBLE DYNAMICS IN A CYLINDRICAL LAMINAR COUETTE
FLOW
Y. Juaneda, C. Colin a
Some results concerning bubble dynamics and migration at low and moderate
bubble Reynolds numbers ReB in a laminar shear flow are presented. Experiments are
performed in normal gravity in laboratory and also in microgravity conditions in
parabolic flights. An experimental device is especially designed to create a shear flow
between two rotating horizontal cylinders of 12 cm and 20 cm diameter. Isolated
bubbles of a few millimeters diameter are injected in the gap between the two
cylinders. In normal gravity, the bubbles may have a stable equilibrium position, which
is used to determine the drag and lift coefficients from a force balance on the bubble.
The effect of bubble deformation and wall vicinity is highlighted. For spherical
bubbles far from the wall, the experimental results (Figure 1) are in agreement with
those of the litterature 1. Near the wall of one cylinder, the lift coefficient drops. The
experimental results are compared to the theoretical study of Magnaudet et al. 2 at low
ReB. For the drag coefficient a good agreement is found between theory and
measurements even for ReB values greater than 1. For the lift coefficients some
discrepancies are oberved close to the wall with the theoretical results at low ReB.
The bubble migration is also investigated. Experiments performed in normal and
microgravity conditions with bubbles of different sizes cover a wide range of bubble
Reynolds numbers ReB from 0.001 to 10. The migration of the bubbles at low ReB has
been theoretically studied in a previous paper 3 and the experimental results are
compared to this study.
Figure 1: Drag coefficients (left) and Lift coefficients (right).
a Institut de Mécanique des Fluides de Toulouse, France
1 Legendre, D., Magnaudet, J., J. Fluid Mech. 368, 81 (1998).
2 Magnaudet et al., J. Fluid Mech., 476, 115 (2003)
3 Juaneda, Y., Colin, C., Mécanique et Industries, 5, 565 (2004).