The thick turbulent boundary layer on a long fine cylinder in axial flow

Experimental and theoretical data on the transverse curvature appearing in axisymmetric flow on a circular cylinder are discussed. Most wind tunnel trials in the past 25 years focused on defining the law of the wall and its relationship to the two-dimensional flow. It has been found that for small boundary layer thickness/cylinder radius ratios (BLCR), the transverse curvature effects are small. Large values of the BLCR are associated with the formation of inner and outer perturbed layers in the flow around the cylinder. Wind tunnel pitot tube measurements of the flow around a wire are reported. No logarithmic profile was observed, although a highly turbulent region was detected close to the cylinder. It is suggested that the flow functions at two different length scales above an Re of 620.