BBAA VI International Colloquium on: Bluff Bodies Aerodynamics & Applications Milano, Italy, July, 20–24 2008 DETACHED-EDDY SIMULATION OF FLOW AROUND A 1:5 RECTANGULAR CYLINDER Claudio Mannini ⋆ , Ante Soda † and G ¨ unter Schewe ◦ ⋆ CRIACIV/Department of Civil and Environmental Engineering University of Florence, Via S. Marta 3, 50139 Firenze, Italy e-mail: claudio.mannini@dicea.unifi.it † Faculty of Mechanical and Naval Engineering University of Zagreb, Ivana Lucica 5, HR-10000 Zagreb, Croatia e-mail: ante.soda@fsb.hr ◦ Institute of Aeroelasticity German Aerospace Center (DLR), Bunsenstraße 10, 37073 G¨ ottingen, Germany e-mails: Guenter.Schewe@dlr.de Keywords: Rectangular Cylinder, Unsteady Aerodynamics, Computational Fluid Dynamics, Turbulence Modelling, DES 1 INTRODUCTION The simulation of unsteady separated flows around bluff bodies is still a challenging issue due to complex physical phenomena such as massive separation and reattachment, laminar-to- turbulent transition and alternating detachment of large eddies. In addition, the flow field is usually three-dimensional, even for simple two-dimensional geometries. The strategy of turbu- lence modelling is particularly important for the simulation of such flows. The employment of unsteady Reynolds-Averaged Navier-Stokes (URANS) equations represent a reasonable choice, given that two-dimensional geometries can be modelled with 2-D meshes and that the required grid resolution is still affordable. Nevertheless, this approach, even when the most advanced turbulence models are used, shows limited accuracy when massive separation and strong curva- ture of streamlines occur (e.g. Ref. [1]). The alternative is to use Large-Eddy Simulation (LES) approach, which is expected to perform better for this type of flows. However, LES requires full three-dimensional grids and it becomes unaffordable when high-Reynolds-number turbulent boundary layers have to be resolved due to the necessary grid refinement (e.g. Ref. [2]). In order to overcome this limit, Detached-Eddy Simulation (DES) was introduced in 1997 (Ref. [2]). It is a hybrid technique based on a definition of the turbulent length scale which allows to switch between RANS approach near solid walls and LES at a certain distance from them, where large vortices can be properly resolved. However, 3-D meshes are needed and consequently the com- putational cost becomes very high, limiting so far the use of this technique to research more than industrial applications. 1