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Simultaneous skin friction and velocity measurements in high Reynolds number pipe and boundary layer flows
- Publication Year :
- 2019
-
Abstract
- Streamwise velocity and wall-shear stress are acquired simultaneously with a hot-wire and an array of azimuthal/spanwise-spaced skin friction sensors in large-scale pipe and boundary layer flow facilities at high Reynolds numbers. These allow for a correlation analysis on a per-scale basis between the velocity and reference skin friction signals to reveal which velocity-based turbulent motions are stochastically coherent with turbulent skin friction. In the logarithmic region, the wall-attached structures in both the pipe and boundary layers show evidence of self-similarity, and the range of scales over which the self-similarity is observed decreases with an increasing azimuthal/spanwise offset between the velocity and the reference skin friction signals. The present empirical observations support the existence of a self-similar range of wall-attached turbulence, which in turn are used to extend the model of Baarset al.(J. Fluid Mech., vol. 823, p. R2) to include the azimuthal/spanwise trends. Furthermore, the region where the self-similarity is observed correspond with the wall height where the mean momentum equation formally admits a self-similar invariant form, and simultaneously where the mean and variance profiles of the streamwise velocity exhibit logarithmic dependence. The experimental observations suggest that the self-similar wall-attached structures follow an aspect ratio of$7:1:1$in the streamwise, spanwise and wall-normal directions, respectively.
- Subjects :
- Physics
Offset (computer science)
Logarithm
Turbulence
Mechanical Engineering
Reynolds number
Mechanics
pipe flow boundary layer
Condensed Matter Physics
boundary layer structure
Azimuth
Physics::Fluid Dynamics
Boundary layer
symbols.namesake
turbulent boundary layers
Mechanics of Materials
Parasitic drag
symbols
Image resolution
Subjects
Details
- Language :
- English
- ISSN :
- 00221120
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....c3f395da00065fd4d1a51749e1f0ace3