Velocity fluctuations for bubbly flows at small Re

Abstract

We experimentally investigate the effect of Reynolds number (Re) on the turbulence induced by the motion of bubbles in a quiescent Newtonian fluid at small Re. The energy spectra, $E(k)$, is determined from the decaying turbulence behind the bubble swarm obtained using particle image velocimetry (PIV). We show that when Re $\sim$ $O$(100), the slope of the normalized energy spectra is no longer independent on the gas volume fraction and the $k^{-3}$ subrange is significantly narrower, where $k$ is the wavenumber. This is further corroborated using second-order longitudinal velocity structure function and spatial correlation of the velocity vector behind the bubble swarm. On further decreasing the bubble Reynolds number ($O(1)<$ Re $<O(10)$), the signature $k^{-3}$ of the energy spectra for the bubble induced turbulence is replaced by $k^{-5/3}$ scaling. Thus, we provide experimental evidence to the claim by \citet{mazzitelli2003effect} that at low Reynolds numbers the normalized energy spectra of the bubble induced turbulence will no longer show the $k^{-3}$ scaling because of the absence of bubble wake and that the energy spectra will depend on the number of bubbles, thus non-universal.

9 pages, 4 figures

References in corpus (5)

• Energy spectra in turbulent bubbly flows
• Experimental investigation of the turbulence induced by a bubble swarm rising within an incident turbulence
• The evolution of energy in flow driven by rising bubbles
• An experimental study on the multiscale properties of turbulence in bubble-laden flows
• Hydrodynamic interaction of a bubble pair in viscoelastic shear-thinning fluids

Cited by in corpus (2)

• Scale-by-scale energy transfers in bubbly flows
• Elastic Pseudoturbulence in Polymer Solutions