Active Near-Wall Flow Control via a Cross Groove with Suction

2015 ◽  
pp. 353-367 ◽  
Author(s):  
I. M. Gorban ◽  
O. V. Khomenko
Keyword(s):  
Flow Control ◽  
Wall Flow ◽  
Near Wall

Entropy-based surface microprofiling for passive near-wall flow control

2007 ◽  
Vol 17 (10) ◽  
pp. 2138-2147 ◽  
Author(s):  
G F Naterer ◽  
S R Chomokovski
Keyword(s):  
Flow Control ◽  
Wall Flow ◽  
Near Wall

scholarly journals In Vitro Study of Near-Wall Flow in a Cerebral Aneurysm Model with and without Coils

2010 ◽  
Vol 31 (8) ◽  
pp. 1521-1528 ◽  
Author(s):  
L. Goubergrits ◽  
B. Thamsen ◽  
A. Berthe ◽  
J. Poethke ◽  
U. Kertzscher ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
In Vitro Study ◽  
Vitro Study ◽  
Wall Flow ◽  
Aneurysm Model ◽  
Near Wall

Highly resolved experimental results of the separated flow in a channel with streamwise periodic constrictions

2016 ◽  
Vol 796 ◽  
pp. 257-284 ◽  
Author(s):  
Christian J. Kähler ◽  
Sven Scharnowski ◽  
Christian Cierpka
Keyword(s):  
Turbulent Flow ◽  
Flow Separation ◽  
Flow Direction ◽  
Separated Flow ◽  
Mean Flow ◽  
Complex Flow ◽  
Flow Measurements ◽  
Flow Features ◽  
Wall Flow ◽  
Near Wall

The understanding and accurate prediction of turbulent flow separation on smooth surfaces is still a challenging task because the separation and the reattachment locations are not fixed in space and time. Consequently, reliable experimental data are essential for the validation of numerical flow simulations and the characterization and analysis of the complex flow physics. However, the uncertainty of the existing near-wall flow measurements make a precise analysis of the near-wall flow features, such as separation/reattachment locations and other predicted near-wall flow features which are under debate, often impossible. Therefore, the periodic hill experiment at TU Munich (ERCOFTAC test case 81) was repeated using high resolution particle image velocimetry and particle tracking velocimetry. The results confirm the strong effect of the spatial resolution on the near-wall flow statistics. Furthermore, it is shown that statistically stable values of the turbulent flow variables can only be obtained for averaging times which are challenging to realize with highly resolved large eddy simulation and direct numerical simulation techniques. Additionally, the analysis implies that regions of correlated velocity fluctuations with rather uniform streamwise momentum exist in the flow. Their size in the mean flow direction can be larger than the hill spacing. The possible impact of the correlated turbulent motion on the wake region is discussed, as this interaction might be important for the understanding and control of the flow separation dynamics on smooth bodies.

The Significance of Flow Unsteadiness on the Near-Wall Flow of a Stented Artery

2009 ◽  
pp. 1947-1950
Author(s):  
Juan Mejia ◽  
Rosaire Mongrain ◽  
Richard Leask ◽  
Josep Cabau-Rodes ◽  
Olivier F. Bertrand
Keyword(s):  
Flow Unsteadiness ◽  
Wall Flow ◽  
Near Wall

Modelling smooth- and transitionally rough-wall turbulent channel flow by leveraging inner–outer interactions and principal component analysis

2019 ◽  
Vol 863 ◽  
pp. 407-453 ◽  
Author(s):  
Sicong Wu ◽  
Kenneth T. Christensen ◽  
Carlos Pantano
Keyword(s):  
Principal Component Analysis ◽  
Outer Layer ◽  
Principal Component ◽  
Turbulent Channel Flow ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Rough Wall ◽  
Smooth Wall ◽  
Wall Flow ◽  
Near Wall

Direct numerical simulations (DNS) of turbulent channel flow over rough surfaces, formed from hexagonally packed arrays of hemispheres on both walls, were performed at friction Reynolds numbers $Re_{\unicode[STIX]{x1D70F}}=200$, $400$ and $600$. The inner normalized roughness height $k^{+}=20$ was maintained for all Reynolds numbers, meaning all flows were classified as transitionally rough. The spacing between hemispheres was varied within $d/k=2$–$4$. The statistical properties of the rough-wall flows were contrasted against a complementary smooth-wall DNS at $Re_{\unicode[STIX]{x1D70F}}=400$ and literature data at $Re_{\unicode[STIX]{x1D70F}}=2003$ revealing strong modifications of the near-wall turbulence, although the outer-layer structure was found to be qualitatively consistent with smooth-wall flow. Amplitude modulation (AM) analysis was used to explore the degree of interaction between the flow in the roughness sublayer and that of the outer layer utilizing all velocity components. This analysis revealed stronger modulation effects, compared to smooth-wall flow, on the near-wall small-scale fluctuations by the larger-scale structures residing in the outer layer irrespective of roughness arrangement and Reynolds number. A predictive inner–outer model based on these interactions, and exploiting principal component analysis (PCA), was developed to predict the statistics of higher-order moments of all velocity fluctuations, thus addressing modelling of anisotropic effects introduced by roughness. The results show excellent agreement between the predicted near-wall statistics up to fourth-order moments compared to the original statistics from the DNS, which highlights the utility of the PCA-enhanced AM model in generating physics-based predictions in both smooth- and rough-wall turbulence.

A Comparison Between Experimental and Predicted Flow Profiles Beneath a Semi-Confined Axisymmetric Impinging Jet

2003 ◽  
Author(s):  
C. Y. Cheong ◽  
P. T. Ireland ◽  
S. Ashforth-Frost
Keyword(s):  
Viscous Flow ◽  
Flow Model ◽  
Three Dimensional ◽  
Impinging Jet ◽  
Theoretical Models ◽  
Velocity Profiles ◽  
Axisymmetric Case ◽  
Air Jet ◽  
Wall Flow ◽  
Near Wall

Theoretical predictions have been compared with experiment for a single semi-confined impinging jet. The turbulent air jet discharged at Re = 20 000 and impinged at nozzle-to-plate spacings (z/d) of 2 and 6.5. Experimental velocity profiles were obtained using hot-wire anemometry. Theoretical velocity profiles were derived using stagnation three-dimensional flow model and viscous flow model for an axisymmetric case. For z/d = 2, velocity profiles in the inviscid region of the near wall flow can be predicted accurately using the stagnation flow model. As the edge of the jet is approached, the flow becomes complex and, as expected, cannot be predicted using the model. Prediction of boundary layer profiles using the viscous flow solution for an axisymmetric case is also reasonable. For z/d = 6.5, the developing impinging jet is essentially turbulent on impact and consequently predictions of near wall flow field, using both the theoretical models, are inappropriate.

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