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Experiments in Fluids

, Volume 37, Issue 3, pp 323–330 | Cite as

Pulsed-wire measurements in the near-wall layer in a reattaching separated flow

  • P. E. HancockEmail author
Original

Abstract

Pulsed-wire velocity measurements have been made in the near-wall layer, including the viscous sublayer, beneath a separated flow. A method for correcting the error caused by fluctuations in velocity gradient is given, extending the work of Schober et al. (1998). The measurements show that the r.m.s. of the streamwise velocity fluctuations scale closely in accordance with an inner-layer scaling, where the velocity scale, \({u}\ifmmode{'}\else$'$\fi_{\tau } \), is based on the r.m.s. of the wall shear stress fluctuations (measured by means of a pulsed-wire shear stress probe), rather than the mean wall shear stress. The effects of velocity gradient are only significant beneath \({{u}\ifmmode{'}\else$'$\fi_{\tau } y} \mathord{\left/ {\vphantom {{{u}\ifmmode{'}\else$'$\fi_{\tau } y} \nu }} \right. \kern-\nulldelimiterspace} \nu \) of 10 or less.

Keywords

Wall Shear Stress Velocity Gradient Laminar Boundary Layer Viscous Sublayer Splitter Plate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

C

Calibration constant

f

Function representing mean velocity

hf

Height of fence above splitter plate surface

L

Length scale of outer-layer structures

s

Distance between pulsed and sensor wires

u

r.m.s. of U

\({u}\ifmmode{'}\else$'$\fi_{\tau } \)

Velocity scale based on r.m.s of wall shear stress fluctuation

U

Instantaneous velocity in x-direction

Um

Instantaneous measured velocity in x-direction

Ur

Free-stream reference velocity

x

Streamwise direction from separation point

y

Distance from splitter plate surface, in normal direction

Xr

Length of separation bubble

δ0

Thickness scale in oscillating layer

η

Blasius laminar boundary layer parameter

ρ

Density

τ

Wall shear stress

τ

r.m.s. of wall shear stress fluctuation

ω

Frequency of oscillating layer

ν

Kinematic viscosity

\({} \)

Overbar denotes time average

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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.School of Engineering, Fluids Research CentreUniversity of SurreyGuildfordUK

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