Mean Wind Loading on Rough-Walled Cooling Towers

Abstract

Mean pressure distributions were measured on a cooling tower model in uniform wind for several longitudinal-rib configurations and two uniformly distributed roughnesses. The base pressure coefficient is shown to be fairly constant along the cooling-tower height and independent of roughness in the range of Reynolds number independence. The difference between the base and minimum pressure coefficients, on the other hand, is shown to decrease with increasing relative roughness or decreasing relative rib spacing if there is not interaction between the flow patterns around consecutive ribs. This results in significant reductions in the magnitude of the negative mean side pressures on the structure and supports the use of strakes on prototypes for the purpose of reducing the mean side sections. The physical mechanisms responsible for the surface roughness effects are identified in the light of the boundary-layer theory. Possible choices as roughness configurations are examined within the limits of the available data.