In this paper, the effect of the flow direction on the bubble distribution and the liquid turbulence was deeply investigated with the developed numerical method. The investigated bubbly flow runs in the vertical channel. For the present numerical method, the liquid-phase velocity field was solved by direct numerical simulations and the microbubble trajectories were tracked by Newtonian equations of motion. The present investigations show the flow direction has the key influence on the phase

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... ribution and the liquidphase turbulence modulation. For the bubbly upflow, the overwhelming majority of microbubbles accumulate near the channel wall, the phase distribution shows approximately the double-peaked distribution pattern, and the liquid-phase turbulence is suppressed. For the bubby downflow, however, microbubbles are far away from the channel wall but move towards the channel centre, the phase distribution shows roughly the offcenter-peaked distribution pattern, and the liquid-phase turbulence is enhanced.