CFD simulation of bubbly two-phase flow in horizontal pipes

The internal phase distribution of co-current, air-water bubbly flow in a 50.3 mm i.d. horizontal pipeline has been modeled using the volume averaged multiphase flow equations. Liquid and gas volumetric superficial velocities varied in the range from 3.8 to 5.1 m/s and 0.2–1.0 m/s, respectively, and average gas volume fraction varied in the range from 4 to 16%. The predicted gas volume fraction and the mean liquid velocity are compared with the experimental data of Kocamustafaogullari and Wang [G. Kocamustafaogullari, Z. Wang, An experimental study on local interfacial parameters in a horizontal bubbly two-phase flow, Int. J. Multiphase Flow 17 (1991) 553–572], Kocamustafaogullari and Huang [G. Kocamustafaogullari, W.D. Huang, Internal structure and interfacial velocity development for bubbly two-phase flow, Nucl. Eng. Des. 151 (1994) 79–101] and Iskandrani and Kojasoy [A. Iskandrani, G. Kojasoy, Local void fraction and velocity field description in horizontal bubbly flow, Nucl. Eng. Des. 204 (2001) 117–128]. Good quantitative agreement with the experimental data is obtained with two different models (i.e., k–ɛ with constant bubble size and k–ɛ with population balance model). The model prediction shows better agreement with the experimental data with population balance than the constant bubble size predictions. The results indicate that the volume fraction has a maximum near the upper pipe wall, and the profiles tend to flatten with increasing liquid flow rate. It was found that increasing the gas flow rate at fixed liquid flow rate would increase the local volume fraction. The axial liquid mean velocity showed a relatively uniform distribution except near the upper pipe wall. An interesting feature of the liquid velocity distribution is that it tends to form a fully developed turbulent pipe-flow profile at the lower part of the pipe irrespective of the liquid and gas superficial velocities.