| الوصف: |
The mathematical up-scaling of gas-liquid bubbly flows was carried out under the framework of the volume averaging theory. A two-fluid model and its associated closure problem were deduced. The closure problem was solved for a case study: a liquid flow past an assembly of homogeneous and monodisperse distorted bubbles. To this end, a cylindrical unit cells with concentric bubbles was used as approach of a representative elementary volume. The following conditions were evaluated: 0 < Re <= 675, 0 < {\epsilon}g <= 0.2, 7.15 x 10-9 <= We <= 3.96 and Mo = 2.55 x 10-11. The interfacial force closure was analyzed in terms of the ratio between the interfacial force for bubbly flow and that existing for a single bubble with the equivalent Re (in an unbounded liquid). It was found that, for creeping regime (0.001 <= Re <= 0.1), the ratio between drag coefficients increases as {\epsilon}g increases independently of Re. For intermediate and inertial regimes (1 <= Re <= 650), the ratio also increases as {\epsilon}g increases; however, two different trends were observed with respect to Re: the ratio decreases for the intermediate regime (1 <= Re <= 50) and increases for the inertial regime (50 < Re <= 650). A transition point around Re = 50 was found, which could be related to the boundary layer formation. Similar trends with respect to existing data from direct numerical simulations of bubbly flows were obtained, showing that this approach represents a good alternative, in terms of computing efforts, to obtain closure laws for two-phase flow modeling. |
