Recent results from direct numerical simulations of deformable bubbles in turbulent flows in vertical channels are discussed. The results show that the lateral migration of the bubbles due to lift forces controls the flow. For upflow, nearly spherical bubbles form a dense bubbly wall-layer but more deformable bubbles stay away from the walls, resulting in very different flow structures and flow rates. The different flow regimes have a very simple structure, but to understand them it is necessary to examine the collective motion of many bubbles rather than individual ones. Here, the effect of bubble deformability and Reynolds number are discussed.

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