Influence of Working Fluid on the Mean Flow Vortex Structure in Industrial Flow Pipelines of Arbitrary Bend Angle via RANS Simulation

Numerical simulations of flow through industrial pipelines is important for design purposes in commercial and domestic transport of oil and gas. In this paper we use steady Computational Fluid Dynamics (CFD) to investigate the effect of different working fluids and streamwise bend angle on the spatial distribution, wall shear stress and turbulence kinetic energy of the fully-developed Dean vortex. Using Ansys Fluent, steady Reynolds-Averaged Navier Stokes (RANS) simulations are performed in a parametric study for various gas flows (air, methane and carbon dioxide) and pipe elbow bend angles (90°,60°,45°,30°,0°). Our results show the flow properties (velocity streamlines, turbulence kinetic energy and induced wall shear stress) of the Dean vortex for inflow velocities ranging from 5 to 15 m/s at Dean numbers of O(104) corresponding to working fluids having the same inflow mass flux. Reducing the pipe bend angle was found to minimize the wall shear stress and subsequent vortex magnitude for all gas flows types. We discuss these results quantitatively in terms of turbulent kinetic energy/the degree of secondary flow comparing to experimental literature. Reference to pipeline longevity is made.