Amin Hassanvand - Polymer engineering department, Faculty of engineering, Lorestan university, khorramabad, lorestan,Iran
S. H. Hashemabadi - Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran, ۱۶۸۴۶, Iran

In this paper, hydrodynamics of the Bubble Train Flows (BTF) in circular capillaries has been investigated by Direct Numerical Simulation (DNS).The volume of fluid based (VOF) interface tracking method and streamwise direction periodic boundary conditions has been applied. In thisapproach the gas volume fraction in unit cell must be set at the beginning of the simulation, this volume fraction remains constant during the simulation and the two phase flow hydrodynamics is affected by this value. The results show that at high gas volume fraction the initial shape of gas bubble may leads to wrong results. For such a condition when the initial bubble shape consists of rectangle and two caps, the desired flow regime is obtained. Our numerical simulations show that for low gas volume fraction (less than 0.5) the rectangular initial bubble shape also leads to good results. The results depict that there exists an appropriate agreement between DNS and experimental correlation results.

Bubble Train Flows (BTF), Direct Numerical Simulation (DNS), Volume of fluid (VOF), Circular Capillaries