Rare backflow and extreme wall-normal velocity fluctuations in near-wall turbulence

2012 ◽  
Vol 24 (3) ◽  
pp. 035110 ◽  
Author(s):  
Peter Lenaers ◽  
Qiang Li ◽  
Geert Brethouwer ◽  
Philipp Schlatter ◽  
Ramis Örlü
Keyword(s):  
Wall Turbulence ◽  
Normal Velocity ◽  
Velocity Fluctuations ◽  
Near Wall Turbulence ◽  
Near Wall

Prediction of near-wall turbulence using minimal flow unit

2018 ◽  
Vol 841 ◽  
pp. 654-673 ◽  
Author(s):  
Guang Yin ◽  
Wei-Xi Huang ◽  
Chun-Xiao Xu
Keyword(s):  
Joint Probability ◽  
Flow Unit ◽  
Wall Turbulence ◽  
Minimal Flow ◽  
Velocity Fluctuations ◽  
Wall Velocity ◽  
Near Wall Turbulence ◽  
Joint Probability Density ◽  
Good Agreement ◽  
Near Wall

In the present study, direct numerical simulation (DNS) is carried out in a minimal channel at $Re_{\unicode[STIX]{x1D70F}}=2000$ to sustain healthy turbulence below $y^{+}=100$. Turbulence intensities are compared with those of the motions at the same scales as the minimal channel in the full-sized channel at $Re_{\unicode[STIX]{x1D70F}}=2003$ (Hoyas & Jiménez, Phys. Fluids, vol. 20 (10), 2008, article 101511). They show good agreement in $y^{+}<100$. The universal signals for the three velocity components similar to that in the predictive model of Marusic et al. (Science, vol. 329 (5988), 2010, pp. 193–196) are extracted from the DNS data of the full-sized channel. They correspond well to the near-wall velocity fluctuations in the minimal flow unit (MFU). The predictive models for the three components of near-wall velocity fluctuations are proposed based on the MFU data. The predicted turbulence intensities as well as the joint probability density functions of velocity fluctuations agree well with the DNS results of the full-sized channel turbulence.

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

Abstract

Non-universal scaling transition of momentum cascade in wall turbulence

2019 ◽  
Vol 871 ◽  
Author(s):  
Xi Chen ◽  
Fazle Hussain ◽  
Zhen-Su She
Keyword(s):  
Wall Turbulence ◽  
Normal Velocity ◽  
Large Set ◽  
Flow State ◽  
Energy Cascades ◽  
Full Coupling ◽  
Turbulent Momentum ◽  
Analytic Prediction ◽  
Prevailing View ◽  
Near Wall

As a counterpart of energy cascade, turbulent momentum cascade (TMC) in the wall-normal direction is important for understanding wall turbulence. Here, we report an analytic prediction of non-universal Reynolds number ($Re_{\unicode[STIX]{x1D70F}}$) scaling transition of the maximum TMC located at $y_{p}$. We show that in viscous units,$y_{p}^{+}$(and$1+\overline{u^{\prime }v^{\prime }}_{p}^{+}$) displays a scaling transition from$Re_{\unicode[STIX]{x1D70F}}^{3/7}$($Re_{\unicode[STIX]{x1D70F}}^{-6/7}$) to$Re_{\unicode[STIX]{x1D70F}}^{3/5}$($Re_{\unicode[STIX]{x1D70F}}^{-3/5}$) in turbulent boundary layer, in sharp contrast to that from$Re_{\unicode[STIX]{x1D70F}}^{1/3}$($Re_{\unicode[STIX]{x1D70F}}^{-2/3}$) to$Re_{\unicode[STIX]{x1D70F}}^{1/2}$($Re_{\unicode[STIX]{x1D70F}}^{-1/2}$) in a channel/pipe, countering the prevailing view of a single universal near-wall scaling. This scaling transition reflects different near-wall motions in the buffer layer for small$Re_{\unicode[STIX]{x1D70F}}$and log layer for large $Re_{\unicode[STIX]{x1D70F}}$, with the non-universality being ascribed to the presence/absence of mean wall-normal velocity $V$. Our predictions are validated by a large set of data, and a probable flow state with a full coupling between momentum and energy cascades beyond a critical$Re_{\unicode[STIX]{x1D70F}}$is envisaged.

Nonlinear analysis of near-wall turbulence time series

1996 ◽  
Vol 57 (3-4) ◽  
pp. 235-261 ◽  
Author(s):  
A. Porporato ◽  
L. Ridolfi
Keyword(s):  
Time Series ◽  
Nonlinear Analysis ◽  
Wall Turbulence ◽  
Near Wall Turbulence ◽  
Near Wall
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