CFD investigation of fluid flow within elbow pipes

Elbow pipes are crucial parts of many fluid transport systems, including ones used in the oil and gas industry. The curved shape of such pipes induces centrifugal forces on the internal flow, ultimately affecting the flow velocity and creating pressure differences within the elbow. The present study is an investigation of the effects of elbow pipes on the flow, and how changing the curvature ratio of an elbow pipe affects the internal flow. The study entails three-dimensional numerical simulations and analysis for laminar internal flows within pipes of varying curvature ratios. For laminar flows, the simulations are based in 4 Reynolds numbers ranging from 200 to 2000 and 3 curvature ratios Ro = 2.8, 5.6 and 11.2. A mesh convergence study is carried out for 3 meshes of increasing resolution. The optimal mesh is then compared to published experimental and numerical results for validation. Once the validation is confirmed, further simulation and analysis is performed for each combination of curvature ratio and Reynolds number. The results reveal that the flow separates due to the centrifugal forces induced by the curved shape. They also show that secondary flows consisting of symmetrical helical vortices called Dean vortices are generated. The intensity of this secondary flow is shown to increase as the Dean number increases