# A time-resolved hot-wire shear stress probe for turbulent flow: use of laminar flow calibration

## Abstract

A specially-designed rotating rig for producing near Couette flow was used in the calibration of a marginally elevated hot-wire shear stress probe. The probe was then used for measurements in both the turbulent boundary layer and pipe flows. Results showed that the mean wall shear stress can be accurately predicted and the near wall statistical quantities of intensity, skewness and flatness of shear stress fluctuations concurred well with previous works, thereby supporting the notion of a time-resolved shear stress probe for turbulent flows.

## Keywords

Boundary Layer Shear Stress Fluid Dynamics Laminar Flow Wall Shear Stress## List of Symbols

*A*Calibration constant in Eq. (4)

*B*Calibration constant in Eq. (4)

*F*Flatness of the shear stress (or velocity) fluctuations

*n*Calibration constant in Eq. (4)

*r*radial coordinate

*Re*_{s}Reynolds number ( ≡

*ωδ*^{2}/*v*)*S*Skewness of the shear stress (or velocity) fluctuations

*u*streamwise velocity

- ū
mean streamwise velocity

*u*_{τ}mean shear velocity,\((\overline {\mathbf{\tau }} / \rho )^{0.5} \)

*y*^{+}height in wall units,

*u*_{τ}y/v*z*vertical coordinate

## Greek symbols

*δ*Gap between the top rotating disk and the bottom stationary disk

*ɛ*dimensionless coordinate,

*z/δ**v*kinematic viscosity

*ϱ*density

*τ*wall shear stress

- τ
mean wall shear stress

*μ*dynamic viscosity

*ω*angular velocity of the top rotating disk

## Subscript

- rms
root-mean-square

*m*independently measured quantities

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## References

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