CFD for multiphase flow in vertical risers

Simulation tools are used extensively for the design and for the improved operations of oil and gas production systems. Most of these simulations are carried out with steady and transient one-dimensional tools, such as PIPESIM, OLGA and LedaFlow. For some applications, however, such as flow in bends, flow in splitters, flow in headers to facilities etc. the one-dimensional assumption limits the prediction accuracy. As an alternative, Computational Fluid Dynamics (CFD) can be used, either for twodimensional and three-dimensional configurations. The study as presented in this paper is focused on the verification and validation of CFD results for multiphase flow of gas and liquid through vertical pipe sections. The open source CFD framework OpenFOAM has been used for this purpose, employing two different multiphase flow methods. The Volume of Fluid method can be used for the capturing of the liquid-gas interfaces, while the two fluid model approach is typically used for dispersed phases. In the present study these two models were combined in a hybrid model and validated using two representative test cases for the vertical pipe. For these two test cases CFD and experimental results are available in the literature, particularly results with Fluent, as presented at a previous BHR conference [1], and with Star-CCM+ as presented in [2].