Friction drag reduction achievable by near-wall turbulence manipulation at high Reynolds numbers

2005 ◽  
Vol 17 (1) ◽  
pp. 011702-011702-4 ◽  
Author(s):  
Kaoru Iwamoto ◽  
Koji Fukagata ◽  
Nobuhide Kasagi ◽  
Yuji Suzuki
Keyword(s):  
Drag Reduction ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Friction Drag ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Friction Drag Reduction ◽  
Near Wall Turbulence ◽  
Turbulence Manipulation ◽  
Near Wall

Perspective: Flow at High Reynolds Number and Over Rough Surfaces—Achilles Heel of CFD

1998 ◽  
Vol 120 (3) ◽  
pp. 434-444 ◽  
Author(s):  
V. C. Patel
Keyword(s):  
Numerical Solutions ◽  
Practical Importance ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Law Of The Wall ◽  
High Reynolds Numbers ◽  
Wall Flow ◽  
High Reynolds ◽  
Near Wall

The law of the wall and related correlations underpin much of current computational fluid dynamics (CFD) software, either directly through use of so-called wall functions or indirectly in near-wall turbulence models. The correlations for near-wall flow become crucial in solution of two problems of great practical importance, namely, in prediction of flow at high Reynolds numbers and in modeling the effects of surface roughness. Although the two problems may appear vastly different from a physical point of view, they share common numerical features. Some results from the ’superpipe’ experiment at Princeton University are analyzed along with those of previous experiments on the boundary layer on an axisymmetric body to identify features of near-wall flow at high Reynolds numbers that are useful in modeling. The study is complemented by a review of some computations in simple and complex flows to reveal the strengths and weaknesses of turbulence models used in modern CFD methods. Similarly, principal results of classical experiments on the effects of sand-grain roughness are reviewed, along with various models proposed to account for these effects in numerical solutions. Models that claim to resolve the near-wall flow are applied to the flow in rough-wall pipes and channels to illustrate their power and limitations. The need for further laboratory and numerical experiments is clarified as a result of this study.

High-Reynolds-number turbulent boundary layer friction drag reduction from wall-injected polymer solutions

2009 ◽  
Vol 621 ◽  
pp. 259-288 ◽  
Author(s):  
E. S. WINKEL ◽  
G. F. OWEIS ◽  
S. A. VANAPALLI ◽  
D. R. DOWLING ◽  
M. PERLIN ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Free Stream ◽  
Polymer Concentration ◽  
Friction Drag ◽  
Molecular Weights ◽  
Development Region ◽  
High Reynolds ◽  
Friction Drag Reduction ◽  
Near Wall

A set of controlled high-Reynolds-number experiments has been conducted at the William B. Morgan Large Cavitation Channel (LCC) in Memphis, Tennessee to investigate the friction drag reduction achieved by injecting aqueous poly(ethylene oxide) (PEO) solutions at three different mean molecular weights into the near-zero-pressure-gradient turbulent boundary layer that forms on a smooth flat test surface having a length of nearly 11m. The test model spanned the 3.05m width of the LCC test section and had an overall length of 12.9m. Skin-friction drag was measured with six floating-plate force balances at downstream-distance-based Reynolds numbers as high as 220 million and free stream speeds up to 20ms−1. For a given polymer type, the level of drag reduction was measured for a range of free stream speeds, polymer injection rates and concentrations of the injected solution. Polymer concentration fields in the near-wall region (0 < y+ < ~103) were examined at three locations downstream of the injector using near-wall planar laser-induced-fluorescence imaging. The development and extent of drag reduction and polymer mixing are compared to previously reported results using the traditional K-factor scaling. Unlike smaller scale and lower speed experiments, speed dependence is observed in the K-scaled results for the higher molecular weight polymers and it is postulated that this dependence is caused by molecular aggregation and/or flow-induced polymer degradation (chain scission). The evolution of near-wall polymer concentration is divided into three regimes: (i) the development region near the injector where drag reduction increases with downstream distance and the polymer is highly inhomogeneous forming filaments near the wall, (ii) the transitional mixing region where drag reduction starts to decrease as the polymer mixes across the boundary layer and where filaments are less pronounced and (iii) the final region where the polymer mixing and dilution is set by the rate of boundary layer growth. Unlike pipe-flow friction-drag reduction, the asymptotic maximum drag reduction (MDR) either was not reached or did not persist in these experiments. Instead, the nearest approach to MDR was transitory and occurred between the development and transitional regions. The length of the development region was observed to increase monotonically with increasing polymer molecular weight, injection rate, concentration and decreasing free stream speed. And finally, the near-wall polymer concentration is correlated to the measured drag reduction for the three polymer molecular weights in the form of a proposed empirical drag-reduction curve.

scholarly journals Reynolds number trend of hierarchies and scale interactions in turbulent boundary layers

2017 ◽  
Vol 375 (2089) ◽  
pp. 20160077 ◽  
Author(s):  
W. J. Baars ◽  
N. Hutchins ◽  
I. Marusic
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Shear Layers ◽  
Wall Turbulence ◽  
Small Scale ◽  
Velocity Fluctuations ◽  
Scale Interaction ◽  
High Reynolds ◽  
Near Wall

Small-scale velocity fluctuations in turbulent boundary layers are often coupled with the larger-scale motions. Studying the nature and extent of this scale interaction allows for a statistically representative description of the small scales over a time scale of the larger, coherent scales. In this study, we consider temporal data from hot-wire anemometry at Reynolds numbers ranging from Re τ ≈2800 to 22 800, in order to reveal how the scale interaction varies with Reynolds number. Large-scale conditional views of the representative amplitude and frequency of the small-scale turbulence, relative to the large-scale features, complement the existing consensus on large-scale modulation of the small-scale dynamics in the near-wall region. Modulation is a type of scale interaction, where the amplitude of the small-scale fluctuations is continuously proportional to the near-wall footprint of the large-scale velocity fluctuations. Aside from this amplitude modulation phenomenon, we reveal the influence of the large-scale motions on the characteristic frequency of the small scales, known as frequency modulation. From the wall-normal trends in the conditional averages of the small-scale properties, it is revealed how the near-wall modulation transitions to an intermittent-type scale arrangement in the log-region. On average, the amplitude of the small-scale velocity fluctuations only deviates from its mean value in a confined temporal domain, the duration of which is fixed in terms of the local Taylor time scale. These concentrated temporal regions are centred on the internal shear layers of the large-scale uniform momentum zones, which exhibit regions of positive and negative streamwise velocity fluctuations. With an increasing scale separation at high Reynolds numbers, this interaction pattern encompasses the features found in studies on internal shear layers and concentrated vorticity fluctuations in high-Reynolds-number wall turbulence. This article is part of the themed issue ‘Toward the development of high-fidelity models of wall turbulence at large Reynolds number’.

The autonomous cycle of near-wall turbulence

1999 ◽  
Vol 389 ◽  
pp. 335-359 ◽  
Author(s):  
JAVIER JIMÉNEZ ◽  
ALFREDO PINELLI
Keyword(s):  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Wall Region ◽  
Streamwise Vortices ◽  
Outer Flow ◽  
Turbulent Fluctuations ◽  
The Mean ◽  
Turbulence Generation ◽  
Near Wall Turbulence ◽  
Near Wall

Numerical experiments on modified turbulent channels at moderate Reynolds numbers are used to differentiate between several possible regeneration cycles for the turbulent fluctuations in wall-bounded flows. It is shown that a cycle exists which is local to the near-wall region and does not depend on the outer flow. It involves the formation of velocity streaks from the advection of the mean profile by streamwise vortices, and the generation of the vortices from the instability of the streaks. Interrupting any of those processes leads to laminarization. The presence of the wall seems to be only necessary to maintain the mean shear. The generation of secondary vorticity at the wall is shown to be of little importance in turbulence generation under natural circumstances. Inhibiting its production increases turbulence intensity and drag.

Bubble friction drag reduction in a high-Reynolds-number flat-plate turbulent boundary layer

2006 ◽  
Vol 552 (-1) ◽  
pp. 353 ◽  
Author(s):  
WENDY C. SANDERS ◽  
ERIC S. WINKEL ◽  
DAVID R. DOWLING ◽  
MARC PERLIN ◽  
STEVEN L. CECCIO
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Flat Plate ◽  
High Reynolds Number ◽  
Friction Drag ◽  
High Reynolds ◽  
Friction Drag Reduction

0605 Visualization of Fluorescently-Labeled Polymer inducing Friction-Drag Reduction Effect in Wall Turbulence

2015 ◽  
Vol 2015 (0) ◽  
pp. _0605-1_-_0605-3_
Author(s):  
Takara ATSUMI ◽  
Hiroya MAMORI ◽  
Kaoru IWAMOTO ◽  
Akira MURATA ◽  
Hirotomo ANDO ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Wall Turbulence ◽  
Friction Drag ◽  
Reduction Effect ◽  
Friction Drag Reduction
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