(577i) On the Influence of Spanwise Boundary Conditions on the Large Eddy Simulation of the Flow Past a Single Cylinder

The flow past a single cylinder has been the focus of scientific investigations due to two major reasons: first, it is a simplified model to study unsteady forces and consequent flow-induced vibrations in many practical applications, for example marine petroleum risers, offshore structures, chimneys and as a component of tubular heat exchangers. Second, as in other bluff body flows, complex phenomena such as shear layer separation and transition to turbulence take place, which make it a classical benchmarking case for the validation of mathematical models. The tridimensional solution of turbulent flows past a single cylinder usually requires approaches of higher computational costs, such as the Large Eddy Simulation (LES). Therefore, simplifications are commonly adopted in the computational domain to allow for reasonable simulation times. One of these simplifications is the use of periodic conditions in the spanwise boundaries of the domain, limiting the spanwise length into an arbitrary value, sometimes guided by the estimated wavelength of the flow structures. This study aims to investigate the validity of the periodic simplification, comparing it to other spanwise boundary conditions and confronting the resulting velocity profiles with experimental data obtained by a two-component Laser Doppler Anemometry system. Simulations were carried out in a commercial Computational Fluid Dynamics (CFD) code with the LES approach at a subcritical Reynolds number. Force and pressure coefficients and the Strouhal number were also compared between the investigated cases, revealing that periodic boundary conditions have considerable influence in the evaluated parameters. Preliminary results show that a symmetry boundary condition is more appropriate than the periodic one in the investigated case, and it should be prioritized in other cases if computational and time resources allow for it.