Impact of Polymer Degradation on Past Studies of the Mean Velocity Profile in Turbulent Boundary Layers

Abstract

This study reexamines past studies of how drag-reducing polymer solutions modify the log-region of a developing turbulent boundary layer (TBL). The classical view was that the polymers modify the intercept constant without impacting the von Kármán coefficient, which results in the log-region being unaltered though shifted outward from the wall. However, recent work has shown this to be not accurate, especially at high drag reduction (HDR) (>40%). While the deviations to the von Kármán coefficient were conjectured to be related to polymeric properties, this had not been explored. This work examines the scatter in both log-region parameters and estimates the local polymeric properties. This shows that the scatter of the von Kármán coefficient between studies is related to the inner variable based Weissenberg number. In addition, recent polymer ocean results are included that support the implicit assumption in past studies that the maximum wall concentration should be used to define the local polymeric properties.