Surface Roughness and Reynolds Number Effects on the Aerodynamic Forces and Pressures Acting on a Semicylindrical Roof in Smooth Flow

AbstractThe effects of surface roughness and Reynolds number on the characteristics of aerodynamic forces and pressures on a semicylindrical roof have been investigated in a wind tunnel. Simultaneous pressure measurements on smooth and rough roofs were obtained under the smooth flow condition. The Reynolds number, based on the cylinder diameter D, was varied from 6.90×104 to 8.28×105 for the smooth roof and from 6.90×104 to 3.31×105 for rough roofs. The surface of the rough roof had a mean relative roughness of k/D=3.0×10−4 to 7.5×10−4 (k is the roughness height). The results indicated that, for a smooth roof, the transition of the separated shear layer occurs in-between R=6.90×104−4.14×105; for rough roofs, the transitional regime is observed at lower Reynolds numbers (in the case of k/D=7.5×10−4, R