Kolmogorov turbulence co-exists with pseudo-turbulence in buoyancy-driven bubbly flows*

Bubble laden flow appears in a variety of natural and industrial processes. A suspension of such bubbles at moderate volume fractions generates complex spatiotemporal flow patterns also known as pseudo-turbulence or bubble-induced agitation. We investigate the spectral properties of buoyancy-driven bubbly flows. We identify the relevant energy transfer mechanisms using high-resolution numerical simulations and phenomenology of homogeneous turbulence. At a high enough Galilei number (ratio of the buoyancy to viscous forces), the kinetic energy spectrum shows the Kolmogorov scaling with a power-law exponent -5/3 for the range of scales between the bubble diameter and the dissipation scale. For scales smaller than the dissipation range, the physics of pseudo-turbulence is recovered.