The role of added mass in the dispersion of bubble clouds

29th IAHR Symposium on Hydraulic Machinery and Systems

Zoghlami, S.^1 ; Béguin, C.^1 ; Etienne, S.^1 ; Scott, D.^2 ; Bornard, L.^2

Polytechnique Montréal, Mechanical Engineering Departement, Canada^1

Hydrodynamics Engineering, Hydro Solutions, GE Renewable Energy, Canada^2

关键词: Added mass tensors;    Bubble dispersion;    Bubble-bubble interaction;    Dissolved oxygen contents;    Euler-euler model;    Euler-lagrange models;    Industrial processs;    Two phase flow model;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/240/6/062050/pdf
DOI  :  10.1088/1755-1315/240/6/062050

来源: IOP

【 摘 要 】

The mechanics of bubble clouds are essential to many industrial processes in the energy and chemical realms. In the specific case of hydroelectric turbines, bubble clouds are present when air is injected into the flow to increase dissolved oxygen content in the water flowing through the power plant. Modeling water flows through hydroelectric turbines already presents many difficulties; adding two-phase flows increases the complexity of the models. In particular, modeling the physics of the phenomena driving the mixing of bubbles in turbines is still a challenge. One important factor in existing two-phase flow models is modeling bubble dispersion. In two-phase flows, bubble dispersion comes from different sources such as turbulence, local pressure conditions and bubble-bubble interactions. In this study, we investigate the effect of added mass on the dispersion of bubbles. In the Euler-Lagrange modeling, the contribution of the added mass force in bubbly flow dispersion was quantified by the development of a repulsive force. This force is a consequence of the added mass variation. We called it the Meshchersky force. For the Euler-Euler model, the dispersion due to the added mass variation was not observed. In fact, the added mass coefficient used in this work was developed as a scalar. It was calculated in the acceleration direction. Thus, the resulting Meshchersky force has the same direction as the velocity. A better modeling would consider the added mass as a tensor rather than a scalar. Therefore, taking into account the void fraction gradient dependency to develop a correlation for the added mass tensor would be a solution to adequately model the added mass and Meshchersky forces, and hence bubble dispersion.