Wind tunnel experiment on effect of shape of an obstacle on total drag force of regular array

Drag coefficients (Cd) and vertical wind profiles for regular arrays were measured in a systematic series of wind tunnel experiment to investigate Hie shape effect of roughness element on Cd and air flow dynamics, and following results were presented. 1) Cd of an array consists of miniature vehicles was compared with that of an array consists of a combination of two different blocks, and the former is 10% to 20% lower than the latter due to the effect of the curved surface, in spite of their similar external scale. 2) The staggered array consists of elements with higher ratio shows larger peak of Cd against roughness density because of the less bluff-body character of a slender obstacle. 3) Turbulent characteristics within canopy layer of an array with high aspect ratio is similar to that of plant canopy.