Numerical simulation of three-dimensional two-phase pipe flows with GPU-accelerated Riemann-based smoothed particle hydrodynamics

The complex interfacial interactions between air and water in pipe drainage process largely affect the pipe flow development and hence becomes a hot topic in urban sewerage engineering. However, current modelling of the air–water interaction behaviour under free flow situations only achieves limited success. While three-dimensional (3D) numerical simulations are highly recommended, they have been seldomly used. This study performs 3D Lagrangian numerical simulations of air–water two-phase pipe flows by adopting a multi-phase smoothed particle hydrodynamics (SPH) method based on the Riemann solver to provide a more realistic description. To enforce the wall boundary conditions a free-slip and no-slip boundary treatment method is presented. As the 3D multi-phase computation demands a massively parallel framework, a GPU implementation is employed to accelerate the massive numerical simulations. Several main aspects of the pipe flow development influenced by the air under different pipe parameters are analysed. The obtained results provide deeper insights into the interaction dynamics of air and water in pipe draining.