Void profiles of air-water bubbly two-phase flow in vertical circular pipe were numerically predicted. The Eulerian-Lagrangian model was used to track the bubble behavior; the interfacial forces acting on bubbles were represented by the constitutive models that were based on the motion of single bubbles. In the present flow condition, the maximum void fraction is often observed near the wall surface at moderate liquid velocity, but its location is shifted towards the pipe center and the peak becomes obscure as the liquid velocity increases. To test whether or not this interesting effect of liquid velocity on radial void distribution in bubbly two-phase flow is appropriately predicted by the present numerical models, the liquid velocity was parametrically changed and the calculated void profiles were compared with available experimental data. As a result, it was revealed that the effect of liquid velocity is successfully expressed by the present models. Since the interfacial lateral forces such as lift force depends on the bubble rise velocity relative to the liquid velocity, appropriate evaluation of the relative velocity was of particular importance in the calculations. For further improvement of the present numerical models, the inclusion of the interaction between bubbles is considered essential.
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