The challenging case of the turbulent flow around a thin plate wind deflector, and its numerical prediction by LES and RANS models

• LES and RANS models prediction of flow over a thin wind deflector plate at small incident angle.
• Mean velocity and pressure were compared to experimental data.
• Second order statistics were evaluated and compared to LES results.
• Error estimate for the anisotropic part of the RANS Reynolds tensor.
• Error estimate for the RANS turbulence force.

The long recirculation bubble found in many industrial applications, mostly involving thin airfoils and thin plate wind deflectors, presents a challenging case for numerical models based on RANS methodology. A deeper understanding of this methodology and its limitations is gained through a series of numerical simulations of the incompressible flow around a thin flat plate of infinite wingspan at small incidences. In this numerically challenging flow, a thin recirculation zone with highly anisotropic turbulent structures is formed close to the leading edge after boundary layer separation. The importance of capturing anisotropy is thoroughly examined and quantitatively assessed in this paper, through a number of simulations employing both large eddy simulations (LES) and Reynolds average Navier–Stokes (RANS) approaches. The former is validated against previous wind tunnel experiment. Since the experimental data does not provide all tensor components to fully assess RANS quality, and LES results can be considered as a reliable source, they are employed in the full characterization of turbulence and in the assessment of the several RANS models predictions presented in this paper. Quantitative results are shown for the errors in capturing the anisotropy part of the Reynolds stress tensor for several RANS models, including Spalart–Almaras, κ−ω SST and transition k−ω SST.