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 ex periment was carried out in a circuit type wind tunnel of a 200 x 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. Th e 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 tes t section, and the spacing was systematically varied to provide S/H = 2, 3, 5, 7, 10, and 13. The mean velocity and turbulence intensities w ere measured by a laser Doppler velocimeter (LDV). It was found that t he spacing ratio S/H = 7 is optimum to augment the turbulence intensit y near the ground plate when the repeated blocks are aligned in a squa re array.