Numerical and experimental studies on the aerodynamics of a 5:1 rectangular cylinder at angles of attack

Abstract

The aerodynamic behavior of a 5:1 rectangular cylinder at angles of attack (AoA) up to 15° is investigated based on Three-dimensional Large-Eddy Simulations (3D LES) and instantaneous pressure measurements. The numerical results indicate that the separated flow is highly sensitive to AoA and involves two patterns: (i) the flow reattaches to the bottom surface and the length reduces as AoA increases, (ii) the separation bubble around the top surface grows with AoA and does not reattach as AoA≥4°. The relationships between flow topology and the pressure statistics are obtained numerically by addressing their distributions in different flow regimes. With respect to these relationships, the differences between the separated-reattached and fully separated flows are determined. On the basis of these relationships, the influence of AoA on the mean, fluctuation, phase difference and, chordwise and spanwise correlations of pressures are studied experimentally. There is a close correspondence between each parameter and the length of the separation bubble, which involves different fluid phenomena in the chordwise and spanwise directions. Furthermore, a weak low-frequency flapping motion is observed in the separation bubble at large AoAs when the main vortex center behind the tail corner. Finally, the influences of AoA on the unsteady and spanwise features of the total forces are analyzed.