The nature of bubble-induced turbulence in polymeric fluids for Re ~ Ο(1)

Recent experimental evidence on bubble-induced turbulence showed that the k ^-3 scaling of the energy spectra of velocity fluctuations is replaced by a steeper k ^-6.8 scaling when polymeric additives are present at a moderate Reynolds number. In the present study, we investigate the homogeneous bubble swarm rising at a low Reynolds number in the polymeric fluid. Using particle image velocimetry (PIV), the liquid velocity fluctuations are determined from the decaying turbulence behind the bubble swarm. In the case of viscous Newtonian fluids (Re ~ Ο(1)), the energy spectrum depends on the gas volume fraction (i.e. the number of bubbles). The present talk addresses an intriguing question of how elasticity affects the energy spectrum in bubble-induced turbulence at a low Reynolds number.