Turbulent boundary layer on a cylinder in axial flow

RESEARCH on the turbulent boundary layer that develops on a cylinder in axial flow is reviewed in the report accompanying this synoptic. Experimental results indicate that the transverse curvature results in a higher coefficient of friction and a “fuller” velocity profile than for a planar boundary layer. However, appropriate scaling laws and nondimensional scaling parameters have been elusive. The few turbulence measurements such as Reynolds stress and intermittency that are available for a cylindrical boundary layer suggest that the distribution of turbulent quantities in the boundary layer is somewhat different from a planar boundary layer, particularly as the boundary layer becomes thick compared to the radius of the cylinder. This is most likely a result of the tendency for a cylindrical boundary layer to become wake-like as the cylinder becomes very small. Measurements of turbulence intensity and detection of turbulence-generating events in a cylindrical boundary layer suggest that the mechanism for the production of turbulence near the wall is similar to that for other wall-bounded flows. However, there is experimental evidence that the outer flow interacts with the nearwall flow to modify the mechanism for the generation of turbulence.