Perturbation of a Turbulent Channel Flow by a two-dimensional Triangular Ripple

2017 ◽  
Author(s):  
Fernando Cúñez ◽  
Erick de Moraes Franklin
Keyword(s):  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Two Dimensional

scholarly journals Streaky structure in a two-dimensional turbulent channel flow.

1985 ◽  
Vol 51 (470) ◽  
pp. 3092-3101 ◽  
Author(s):  
Yoichiro IRITANI ◽  
Nobuhide KASAGI ◽  
Masaru HIRATA
Keyword(s):  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Two Dimensional ◽  
Streaky Structure

An Analytical Study of the Standard k–ε Model

1990 ◽  
Vol 112 (2) ◽  
pp. 192-198 ◽  
Author(s):  
N. Takemitsu
Keyword(s):  
Experimental Data ◽  
Asymptotic Solution ◽  
Channel Flow ◽  
Analytical Study ◽  
Turbulent Channel Flow ◽  
Second Order ◽  
Two Dimensional ◽  
Ill Posed ◽  
Leading Term ◽  
Logarithmic Law

An asymptotic solution of the standard k–ε model for two-dimensional turbulent channel flow is found. Using this solution, five model constants in the model are all determined reasonably with the aid of experimental data. If an asymptotic solution with the logarithmic law as the leading term is sought for, the standard k–ε model is shown to be ill-posed since the second-order solution has divergent terms.

Wavelet analysis on the drag-reducing characteristics of turbulent channel flow with surfactant additive based on experimental data

2017 ◽  
Vol 95 (11) ◽  
pp. 1115-1121 ◽  
Author(s):  
Lu Wang ◽  
Zhi-Ying Zheng ◽  
Jia-Qi Bao ◽  
Tong-Zhou Wei ◽  
Wei-Hua Cai ◽  
...  
Keyword(s):  
Channel Flow ◽  
Coherent Structures ◽  
Turbulent Channel Flow ◽  
Discrete Wavelet ◽  
Two Dimensional ◽  
Solution Flow ◽  
Multi Scale ◽  
Turbulent Channel Flows ◽  
Scale Characteristics ◽  
Cetyltrimethyl Ammonium

Two-dimensional velocity fields for turbulent channel flows of water and 50 ppm CTAC/NaSal (cetyltrimethyl ammonium chloride/sodium salicylate) solution were experimentally obtained by particle image velocimetry. Multi-scale decompositions of the fluctuating velocity signals were performed by two-dimensional binary orthogonal discrete wavelet to analyze the influence of surfactant additives on the multi-scale characteristics of turbulent channel flow. From the results of wavelet multi-scale decompositions, it can be observed that the quantity of coherent structures near the wall in CTAC solution flow is decreased obviously. The results of the flatness factor show that the addition of drag-reducing additives inhibits the intermittency in turbulence. By analyzing the distribution of local intermittence measure and local Reynolds shear measure, it is found that the intermittency mainly concentrates near the wall, and the intermittent region distinctly reduces in CTAC solution flow compared with that in water flow. By combining the analysis of the motion of coherent structures in turbulent channel flow, it is shown that surfactant additives mainly and distinctly impact the coherent structures near the wall, especially in the viscous layer.

scholarly journals Simultaneous Stereo PIV and MPS3 Wall-Shear Stress Measurements in Turbulent Channel Flow

Optics ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 40-51
Author(s):  
Esther Mäteling ◽  
Michael Klaas ◽  
Wolfgang Schröder
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Channel Flow ◽  
Inclination Angle ◽  
Large Scale ◽  
Turbulent Channel Flow ◽  
Two Dimensional ◽  
Velocity Fluctuations ◽  
Wall Shear ◽  
Near Wall

An extended experimental method is presented in which the micro-pillar shear-stress sensor (MPS 3 ) and high-speed stereo particle-image velocimetry measurements are simultaneously performed in turbulent channel flow to conduct concurrent time-resolved measurements of the two-dimensional wall-shear stress (WSS) distribution and the velocity field in the outer flow. The extended experimental setup, which involves a modified MPS 3 measurement setup and data evaluation compared to the standard method, is presented and used to investigate the footprint of the outer, large-scale motions (LSM) onto the near-wall small-scale motions. The measurements were performed in a fully developed, turbulent channel flow at a friction Reynolds number R e τ = 969 . A separation between large and small scales of the velocity fluctuations and the WSS fluctuations was performed by two-dimensional empirical mode decomposition. A subsequent cross-correlation analysis between the large-scale velocity fluctuations and the large-scale WSS fluctuations shows that the streamwise inclination angle between the LSM in the outer layer and the large-scale footprint imposed onto the near-wall dynamics has a mean value of Θ ¯ x = 16.53 ∘ , which is consistent with the literature relying on direct numerical simulations and hot-wire anemometry data. When also considering the spatial shift in the spanwise direction, the mean inclination angle reduces to Θ ¯ x z = 13.92 ∘ .

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