Effects of turbulence intensity and integral length scale on the surface pressure on a rectangular 5:1 cylinder

This paper presents the LES of the turbulence effects on the flow over a two-dimensional rectangular 5:1 cylinder. The homogeneous and isotropic inflow turbulence fields are generated by the Iterating-Reshaping based Consistent Discrete Random Flow Generation (IRCDRFG) technique. A total of nine numerical cases with the inflow turbulence intensity equal to 5.0%, 7.5%, and 10.0%, and the ratio of integral length scale to cylinder depth (L/D) equal to 1, 2, and 4 are simulated respectively. The LES tool well reproduces both the instantaneous and time-averaged flow structures in the near cylinder area. The sizes of the mean separation bubble on the cylinder surface are noticed to decrease and be closer to the leading edge with the higher turbulence intensity and the lower L/D, which contributes to the shift of location with the minimum mean value and that with the maximum RMS value of the surface pressure. Besides, the consistent drag force results with different inflow conditions are obtained, which have strong connection with the following correlation results of surface pressure in different directions. Additionally, the PSD analysis shows that the low-frequency energy of the fluctuating pressure is significantly increased with the presence of the incoming large-scale turbulence field.