Unsteady flow characteristics behind a triangular-shaped bluff body were experimentally investigated in a water flow of the Reynolds number range ReD = 500∼3000. The effect of changing the blockage ratio, BR, from BR = 0.2 to 0.6, was investigated. The experimental data of the velocity were obtained by using cinematic particle image velocimetry (PIV) to map the unsteady velocity field around the vortex-generating region. Based on the measured data, influences of the blockage on time-averaged velocities, turbulence intensity distributions and Strouhal number were examined. Moreover, proper orthogonal decomposition (POD) was performed on fluctuating vorticity fields to identify the most energetic parts of the vorticity fluctuations.

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