Drag of bluff body immersed in a rough wall boundary layer.

Reports experiments carried out in a wind tunnel on two kinds of two-dimensional roughness arrays and on one array of three-dimensional roughness with a turbulent boundary layer growing over the arrays. Drag coefficient on an individual element was measured by pressure tapping as its height was varied relative to the average height of the array. Some general forms for the drag coefficients are found for the two-dimensional case. Results for the three dimensional case show some general trends but more work is needed.