Effect of Wind-Tunnel Walls on the Flow Past Circular Cylinders and Cooling Tower Models

The effect of wind tunnel walls on the mean pressure distributions on rough-walled circular cylinders and on cooling tower models fitted with longitudinal ribs is studied experimentally in the range of Reynolds-number independence. For circular cylinders the results are compared with analytical corrections based on formulae of Allen and Vincenti, and of Maskell, which are found to be generally applicable in this Reynolds number range. For cooling towers, a correction procedure is proposed using the base pressure coefficient, C_pb, and the dimensionless pressure rise to separation, C_pb–C_pm, where C_pm is the minimum value of the pressure coefficient. The base pressure coefficient C_pb for cooling towers is (in the Reynolds-number-independent range) a function of the boundary geometry: model shape, tunnel type (open or closed jet) and blockage, and is independent of surface roughness. The difference C_pb–C_pm, on the other hand, is mainly a function of surface roughness for both cylinders and cooling towers and is very little, if at all, affected by tunnel blockage for blockages less than, say, 15 percent.