Wall-shear-stress and near-wall turbulence measurements up to single pixel resolution by means of long-distance micro-PIV

2006 ◽  
Vol 41 (2) ◽  
pp. 327-341 ◽  
Author(s):  
C. J. Kähler ◽  
U. Scholz ◽  
J. Ortmanns
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Wall Turbulence ◽  
Long Distance ◽  
Pixel Resolution ◽  
Turbulence Measurements ◽  
Micro Piv ◽  
Near Wall Turbulence ◽  
Single Pixel ◽  
Near Wall

Shear stress-driven flow: the state space of near-wall turbulence as

2019 ◽  
Vol 874 ◽  
pp. 606-638 ◽  
Author(s):  
Patrick Doohan ◽  
Ashley P. Willis ◽  
Yongyun Hwang
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Couette Flow ◽  
Poiseuille Flow ◽  
Wall Turbulence ◽  
Phase Portraits ◽  
Wall Region ◽  
Velocity Statistics ◽  
Near Wall Turbulence ◽  
Near Wall

An inner-scaled, shear stress-driven flow is considered as a model of independent near-wall turbulence as the friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}\rightarrow \infty$. In this limit, the model is applicable to the near-wall region and the lower part of the logarithmic layer of various parallel shear flows, including turbulent Couette flow, Poiseuille flow and Hagen–Poiseuille flow. The model is validated against damped Couette flow and there is excellent agreement between the velocity statistics and spectra for the wall-normal height $y^{+}<40$. A near-wall flow domain of similar size to the minimal unit is analysed from a dynamical systems perspective. The edge and fifteen invariant solutions are computed, the first discovered for this flow configuration. Through continuation in the spanwise width $L_{z}^{+}$, the bifurcation behaviour of the solutions over the domain size is investigated. The physical properties of the solutions are explored through phase portraits, including the energy input and dissipation plane, and streak, roll and wave energy space. Finally, a Reynolds number is defined in outer units and the high-$Re$ asymptotic behaviour of the equilibria is studied. Three lower branch solutions are found to scale consistently with vortex–wave interaction (VWI) theory, with wave forcing localising around the critical layer.

On the method of determining instantaneous wall shear stress from near-wall velocity measurements in wall turbulence

2021 ◽  
Vol 33 (12) ◽  
pp. 125105
Author(s):  
Qigang Chen ◽  
Yanchong Duan ◽  
Qiang Zhong ◽  
Zhongxiang Wang ◽  
Lei Huang
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Wall Turbulence ◽  
Velocity Measurements ◽  
Wall Velocity ◽  
Wall Shear ◽  
Near Wall

scholarly journals Spectral Characteristics of the Near-Wall Turbulence in an Unsteady Channel Flow

2005 ◽  
Vol 74 (1) ◽  
pp. 172-175 ◽  
Author(s):  
Sedat F. Tardu
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Channel Flow ◽  
Spectral Characteristics ◽  
Time Lag ◽  
Wall Turbulence ◽  
Centerline Velocity ◽  
Wall Shear ◽  
Unsteady Channel Flow ◽  
Near Wall

The modulation characteristics of the turbulent wall shear stress and longitudinal intensities in the inner layer are experimentally investigated in an unsteady channel flow wherein the centerline velocity varies in time in a sinusoidal manner. The fluctuating wall shear stress and velocity signals are temporally filtered and subsequently phase averaged. It is shown that the outer structures corresponding to the low spectrum range have a constant time lag with respect to the centerline velocity modulation. The inner active structures, in particular those with a frequency band containing the mean ejection frequency of the corresponding steady flow dominate the dynamics of the near-wall unsteady turbulence. The structures respond to the imposed shear oscillations in a complex way, depending both on their characteristic scales and the thickness of the oscillating shear zone in which they are embedded.

Mechanism of control of the near-wall turbulence using a micro-cavity array

2021 ◽  
Vol 33 (7) ◽  
pp. 075114
Author(s):  
S. S. Bhat ◽  
A. Silvestri ◽  
B. S. Cazzolato ◽  
M. Arjomandi
Keyword(s):  
Wall Turbulence ◽  
Micro Cavity ◽  
Near Wall Turbulence ◽  
Cavity Array ◽  
Near Wall

scholarly journals Minimal multi-scale dynamics of near-wall turbulence

2021 ◽  
Vol 913 ◽  
Author(s):  
Patrick Doohan ◽  
Ashley P. Willis ◽  
Yongyun Hwang
Keyword(s):  
Wall Turbulence ◽  
Multi Scale ◽  
Near Wall Turbulence ◽  
Near Wall

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