Author(s): Stephane Etienne

Linked Author(s):

Keywords: Two phase flow; Dispersion; Added mass; Euler-Euler; Interface forces;

Abstract: The mechanics of bubble clouds are essential to develop more efficient and ecological aerating turbines. Due to the complexity of the two-phase flow configurations, modeling the physics of the phenomena driving the mixing of bubbles in turbines is still a challenge. One important factor, in existing two-phase flowmodels, is understanding small bubble dispersion. This behavior comes from different sources such as turbulence, local pressure conditions and bubble to bubble interactions. In this study, we model the effect of added mass fluctuations on the dispersion of bubbles. It was proven that for the Euler-Euler approach, actual added mass models do not consider its local variations due to bubbles distribution. Thus, the dispersion effect of the added mass force cannot be captured. Therefore, we use models, previously developed in our group, solving the potential flow around N bubbles, to consider a complete representation of the added mass effects on bubble clouds. We propose a complete added mass model that includes local bubble configuration by introducing the void fraction gradient. In fact, we consider the added mass as a tensor rather than a scalar. The void fraction gradient allows us to account for the asymmetry of the bubble cloud around a single central bubble. This methodology results in a more consistent added mass effect as well as Meshchersky forces, to be included in hydrodynamic models. Thus, this approach can be implemented in an Euler-Euler model that considers the dispersion of small bubbles caused by the effect of addedmass.

DOI: https://doi.org/10.3850/38WC092019-1235

Year: 2019