• visualizzazione
• simulazione
• les
• fluidodinamica
• cilindro

The present work is a part of a computational contribution to the Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder, BARC. The problem is of interest not only for the purpose of fundamental research, but also to provide useful information on the aerodynamics of a wide range of bluff bodies of interest in civil engineering (e.g. tall buildings, towers and bridges) and for other engineering applications. The 5:1 aspect ratio is characterized by shear-layers detaching at the upstream cylinder corners and reattaching on the cylinder side rather close the downstream corners. This leads to a complex dynamics and topology of the flow on the cylinder side, which adds to the vortex shedding from the rear corners and to the unsteady dynamics of the wake.

Variational multiscale large-eddy simulation (VMS-LES)is used in the present thesis. Two different eddy-viscosity subgrid scale (SGS) models are adopted to close the VMS-LES equations, viz. the Smagorinsky model and the WALE models.
A proprietary research code is used, which is based on a mixed finite-volume/finite-element method applicable to unstructured grids for space discretization and on linearized implicit time advancing. Two different unstructured grids are considered; similarly two Reynolds numbers values are investigated (Re=20000 and 40000 based on the freestream velocity and on the cylinder depth).
The results obtained are assessed by comparison against other available numerical results and experimental data. The present thesis particularly focuses on the investigation of the vorticity dynamics on the cylinder lateral sides by means of instantaneous flow visualizations; typical vortex configurations are identified.