Low-Reynolds-Number Turbulent Boundary Layers

This paper presents experimental wind-tunnel data that show the universal logarithmic velocity profile for zero-pressure-gradient turbulent boundary layer flows is valid for values of momentum-deficit Reynolds numbers R_θ as low as 600. However, for values of R_θ between 425 and 600, the von Ka´rma´n and additive constants vary and are shown to be functions of R_θ and shape factor H. Furthermore, the viscous sublayer in the range 425<R_θ<600 can no longer maintain its characteristically small size. It is forced to grow, due to viscous effects, into a super sublayer (6-9 percent of the boundary layer height) that greatly exceeds conventional predictions of sublayer heights.