Abstract
The motion of single bubbles in turbulent flow field in vertical ducts was calculated using a two-way bubble tracking method, in which Eulerian and Lagrangian descriptions are used for continuous liquid phase and individual bubbles, respectively. It is considered in the present flow condition that the oscillatory motion of bubbles is caused by the interaction between the bubble and shear-induced turbulent eddy produced in the surrounding liquid; furthermore, it has been experimentally observed even in stagnant liquid that the oscillation of bubble rise path is induced by the fluctuation of wake structure formed behind the bubble. For these reasons, in the calculations, the fluctuating components associated with the shear-induced turbulence and the wake structure behind the rising bubble were added to the mean velocity of liquid phase in a stochastic manner, which enabled to express the oscillatory motion of bubbles. Since these fluctuating components are associated with different mechanisms, their amplitudes and time scales were estimated separately. As a result of several numerical calculations, it was demonstrated that the statistical features of the motion of single bubbles observed in several experiments are to be reasonably predicted with the present method.
