Aerodynamic characteristics of a 5:1 rectangular cylinder at Reynolds numbers of 3.12 × 105 to 1.01 × 106

Rectangular cylinders with a ratio of 5:1 are extensively applied in engineering structures. Their aerodynamic characteristics, especially at high Reynolds numbers (Re), remain unclear. A series of force and wind pressure measurement tests at high Reynolds numbers are conducted on a 5:1 rectangular cylinder, with angles of attack ranging from 0° to 8°. The results show that the mean drag coefficient, moment coefficient, and Strouhal number exhibit significant Reynolds number effects, with noticeable angle of attack variations. At nonzero angles of attack, the probability density function curve of the lift coefficient changes from bimodal to unimodal with increasing Reynolds number, and the transition Reynolds number decreases with the increase in angles of attack. As the angle of attack increases, the vortex core on the upper surface moves downstream, whereas the opposite occurs on the lower surface. When the angle of attack equals or exceeds 2°, the reattachment point on the upper surface disappears. The effect of the Reynolds number on the mean pressure coefficient is negligible, whereas the fluctuating pressure coefficient at the rear of the upper and lower surfaces notably decreases with the increasing Reynolds number. The overall shape of the mean and fluctuating pressure coefficient distributions is unaffected by the Reynolds number. Vortex shedding dominates fluctuations of pressure on top and bottom surfaces. As the angle of attack increases, the pressure coefficient spectra minimum peak amplitude distribution shifts backward on the top surface and forward on the bottom, likely due to the movement of the vortex core.