Mechanism Study on Bubble Dynamics in Rectangular Pipes Based on CFD Method

Numerical simulation on the movement of a single bubble as well as double bubbles was conducted with the VOF model based on computed fluid dynamics（CFD）. The simulation results agree well with the experimental observations. For a single bubble, the rising process includes accelerating vertically and swinging up. At the later stage, the trajectory is sinusoidal. The bubble’s stable velocity is determined by Eo number. For the two bubbles, coalescence may occur with an up-and-down structure. On the other hand, with a horizontal distribution, the two bubbles will separate and draw near regularly. The latter two decide the radial distribution of bubbles. From the results, the CFD method can well simulate the movement of bubbles, which is the basis of further study on bubble distribution with different buoyancies in natural circulation.