  Data from Direct Numerical Simulations of disperse bubbly flows in a vertical
channel are used to study the effect of the bubbles on the carrier-phase
turbulence. A new method is developed, based on the barycentric map approach,
that allows to quantify the anisotropy and componentiality of the flow at any
scale. Using this the bubbles are found to significantly enhance flow
anisotropy at all scales compared with the unladen case, and for some bubble
cases, very strong anisotropy persists down to the smallest flow scales. The
strongest anisotropy observed was for the cases involving small bubbles.
Concerning the inter-scale energy transfer, our results indicate that for the
bubble-laden cases, the energy transfer is from large to small scales, just as
for the unladen case. However, there is evidence of an upscale transfer when
considering the transfer of energy associated with particular components of the
velocity field. Although the direction of the energy transfer is the same with
and without the bubbles, the transfer is much stronger for the bubble-laden
cases, suggesting that the bubbles play a strong role in enhancing the activity
of the nonlinear term in the flow. The normalized forms of the fourth and
sixth-order structure functions are also considered, and reveal that the
introduction of bubbles into the flow strongly enhances intermittency in the
dissipation range, but suppresses it at larger scales. This strong enhancement
of the dissipation scale intermittency has significant implications for
understanding how the bubbles might modify the mixing properties of turbulent
flows.
