Turbulent near-wakes of periodic array of square blocks on a plate

This paper describes the experimental study of the flow structure past square blocks located on a ground plate with various spacings. The experiment was carried out in a circuit type wind tunnel of a 200 × 200 mm working section and 2000 mm in length at a Reynolds number of 990, which is based on the free-stream velocity and the height of block. The test blocks, side length D = 23 mm and height H = 5 mm, were aligned at a regular spacing S in a square array on the lower wall of the test section, and the spacing was systematically varied to provide S/H = 2, 3, 5, 7, 10, and 13. The mean velocity and turbulence intensities were measured by a laser Doppler velocimeter (LDV). It was found that the spacing ratio S/H = 7 is optimum to augment the turbulence intensity near the ground plate when the repeated blocks are aligned in a square array.