Hybrid Eulerian Eulerian Discrete Phase Model of Turbulent Bubbly Flow

The Eulerian-Eulerian two-fluid model [1] (EE) is the most general model in multiphase flow computations. One limitation of the EE model is that it has no ability to estimate the local bubble sizes by itself. Thus, it must be complemented either by measurements of bubble size distribution or by additional models such as population balance theory or interfacial area concentration to get the local bubble size information. In this work, we have combined the Discrete Phase model (DPM) [2,8] to estimate the evolution of bubble sizes with the Eulerian-Eulerian model. The bubbles are tracked individually as point masses, and the change of bubble size distribution is estimated by additional coalescence and breakup modeling of the bubbles. The time varying bubble distribution is used to compute the local interface area between gas and liquid phase, which is used to estimate the momentum interactions such as drag, lift, wall lubrication and turbulent dispersion forces. This model is applied to compute an upward flowing bubbly flow in a vertical pipe and the results are compared with previous experimental work of Hibiki et al. [3]. The newly developed hybrid model (EEDPM) is able to reasonably predict the locally different bubble sizes and the velocity and void fraction fields. On the other hand, the standard EE model without the DPM shows good comparison with measurements only when the prescribed constant initial bubble size is accurate and does not change much.