Numerical Investigation of 3D Flow around Two Tandem Cylinders

Abstract

Circular cylinders in tandem arrangement are frequently encountered in marine applications, for example as dual pipelines and dual risers. Complex flows arise around tandem cylinders, inducing large fluctuating forces on them. In this study, 3D flow around two tandem circular cylinders is numerically simulated using Large Eddy Simulations (LES) with Smagorinsky subgrid scale model: through the open-source code OpenFOAM. The cylinders are immersed in an infinite fluid and a steady current at intermediate subcritical Reynolds number (Re = 1.31 x 104 ). The center-to-center spacing between the cylinders is 5 diameters (S/D=5). The results are presented through the vorticity distribution, the mean velocity distributions, the root-mean-square (RMS) pressure distribution and the time series of the drag- and the lift coefficients. Special attention is given to explaining the physics of the flow in the spacing region. Surface streamlines are used to visualize the flow separation on both cylinders and the impingement location on the downstream cylinder. This representation has, to the knowledge of these authors, not been published before. The results of the drag and lift coefficients and the RMS pressure coefficient are compared with the previously published experimental measurements and comparable numerical simulations. A good agreement with previous research is accomplished. The flow for the given spacing proved to be in the coshedding regime, where the vortices form and shed behind the upstream cylinder: and impinge the downstream cylinder. Synchronized with the impingement, the vortices are shed behind the downstream cylinder.