Coherent Structure of Surface Pressures on 2-D Rectangular Cylinders in Turbulent Flow

The aerodynamic forces due to wind turbulence indicate higher span-wise coherence as reported in the literature. To develop the buffeting response analysis method with more accuracy, and to understand the effect of turbulence on the aerodynamic forces, it is necessary to observe the coherent structure of surface pressures on a bluff body, systematically. In this study, surface pressures on a 2-D rectangular cylinder in grid turbulence were measured simultaneously at many pressure taps. Side ratio of the model cross section was selected from B/D=0.5 to 5.0 (B: stream-wise width of rectangular cross section, D: lateral height of rectangular cross section). The coherent structure of surface pressures is to be discussed. As for the relatively slender cross section, the span-wise correlation length of the lift force is found to be proportional to that of approaching wind velocity. While, the span-wise coherence of surface pressures for the side ratio B/D=0.5, the significant increase in the coherence due to the Karman vortex was observed. Temporal variation of the span-wise correlation is to be discussed as well.