Quantitative characterization of coherent structures in the buffer layer of near-wall turbulence. Part 1: streaks

2008 ◽  
Vol 45 (6) ◽  
pp. 999-1013 ◽  
Author(s):  
J. Lin ◽  
J. P. Laval ◽  
J. M. Foucaut ◽  
M. Stanislas
Keyword(s):  
Buffer Layer ◽  
Coherent Structures ◽  
Wall Turbulence ◽  
Quantitative Characterization ◽  
Near Wall Turbulence ◽  
Near Wall

Validation of Turbulence Models for the Superlaminar Flows in Journal Bearings

2017 ◽  
Author(s):  
Aoshuang Ding ◽  
Xiaodong Ren
Keyword(s):  
Buffer Layer ◽  
Turbulence Models ◽  
Journal Bearings ◽  
Wall Turbulence ◽  
Fully Developed Turbulence ◽  
Developed Turbulence ◽  
Sst Model ◽  
Oil Flow ◽  
Near Wall Turbulence ◽  
Near Wall

With the development of high speed rotating machinery, the flow regime in bearings changes from laminar to superlaminar, that is, the flow is between laminar and fully developed turbulent. The superlaminar oil flow in an oil–lubricated tilting–pad journal bearing is analyzed in this study. A three–dimensional model for the oil domain is established and the CFD results obtained using laminar and seventeen turbulence models are compared with the experimental results obtained by S.Taniguchi. The seventeen turbulence models are divided into three groups, namely, classical fully developed turbulence models, transition turbulence models, and turbulence models with low–Re correction. The laminar and classical turbulence models cannot simulate the superlaminar flow correctly; accordingly, corrections should be applied to classical fully developed turbulence models for superlaminar flows to consider the turbulent effect properly. However, not all corrections are suitable. Among all the compared turbulence models, the SST model with low–Re correction performs the best. Furthermore, this model can capture the turbulent effect in superlaminar oil flow, as indicated in the analysis of turbulent viscosity ratio. A comparison of the velocity profiles shows that the mechanism of the superlaminar flow in journal bearings is near–wall turbulence. The buffer layer plays an important role in superlaminar flows. The SST model with low–Re correction can likewise capture the characteristics of the buffer layer and simulate the near–wall turbulence properly in superlaminar flows. Thus in superlaminar journal bearings, the low–Re correction is the most suitable correction for the SST turbulence model for simulating oil flows.

scholarly journals Characterization of near-wall turbulence in terms of equilibrium and “bursting” solutions

2005 ◽  
Vol 17 (1) ◽  
pp. 015105 ◽  
Author(s):  
Javier Jiménez ◽  
Genta Kawahara ◽  
Mark P. Simens ◽  
Masato Nagata ◽  
Makoto Shiba
Keyword(s):  
Wall Turbulence ◽  
Near Wall Turbulence ◽  
Near Wall

scholarly journals Extracting Coherent Structures in Near-Wall Turbulence Based on Wavelet Analysis

2020 ◽  
Author(s):  
Peng Du ◽  
Haibao Hu ◽  
Xiao Huang
Keyword(s):  
Boundary Layer ◽  
Coherent Structures ◽  
Extraction Method ◽  
Extraction Procedure ◽  
Probability Density Functions ◽  
Wall Turbulence ◽  
Spectrum Density ◽  
Hot Film ◽  
Near Wall Turbulence ◽  
Near Wall

To analyze the properties of the coherent structures in near-wall turbulence, an extraction method based on wavelet transform (WT) and a verification procedure based on correlation analysis are proposed in this work. The flow field of the turbulent boundary layer is measured using the hot-film anemometer in a gravitational low-speed water tunnel. The obtained velocity profile and turbulence intensity are validated with traditional boundary layer theory. The fluctuating velocities at three testing positions are analyzed. Using the power spectrum density (PSD) and WT, coherent and incoherent parts of the near-wall turbulence are extracted and analyzed. The probability density functions (PDFs) of the extracted signals indicate that the incoherent structures of turbulence obey the Gaussian distribution, while the coherent structures deviate from it. The PDFs of coherent structures and original turbulence signals are similar, which means that coherent structures make the most contributions to the turbulence entrainment. A correlation parameter is defined at last to prove the validity of our extraction procedure.

Extraction and verification of coherent structures in near-wall turbulence

2013 ◽  
Vol 22 (7) ◽  
pp. 074703 ◽  
Author(s):  
Hai-Bao Hu ◽  
Peng Du ◽  
Su-He Huang ◽  
Ying Wang
Keyword(s):  
Coherent Structures ◽  
Wall Turbulence ◽  
Near Wall Turbulence ◽  
Near Wall

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
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