A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation

2016 ◽  
Vol 54 (6) ◽  
pp. 663-677 ◽  
Author(s):  
Farzad Ferdos ◽  
Bijan Dargahi
Keyword(s):  
Porous Media ◽  
Turbulent Flow ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Numerical Validation ◽  
High Reynolds Numbers ◽  
High Reynolds

Turbulent flow between counter-rotating concentric cylinders: a direct numerical simulation study

2008 ◽  
Vol 615 ◽  
pp. 371-399 ◽  
Author(s):  
S. DONG
Keyword(s):  
Turbulent Flow ◽  
Large Scale ◽  
Outer Cylinder ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Taylor Vortex ◽  
Small Scale ◽  
Mean Flow ◽  
Concentric Cylinders ◽  
High Reynolds

We report three-dimensional direct numerical simulations of the turbulent flow between counter-rotating concentric cylinders with a radius ratio 0.5. The inner- and outer-cylinder Reynolds numbers have the same magnitude, which ranges from 500 to 4000 in the simulations. We show that with the increase of Reynolds number, the prevailing structures in the flow are azimuthal vortices with scales much smaller than the cylinder gap. At high Reynolds numbers, while the instantaneous small-scale vortices permeate the entire domain, the large-scale Taylor vortex motions manifested by the time-averaged field do not penetrate a layer of fluid near the outer cylinder. Comparisons between the standard Taylor–Couette system (rotating inner cylinder, fixed outer cylinder) and the counter-rotating system demonstrate the profound effects of the Coriolis force on the mean flow and other statistical quantities. The dynamical and statistical features of the flow have been investigated in detail.

Vorticity Field and Acoustic Sources in a Turbulent Flow at Very Low Mach and High Reynolds Numbers

2005 ◽  
Author(s):  
Jean Brac ◽  
Pierre-Yves Lanfrey ◽  
Pierre Sagaut
Keyword(s):  
Turbulent Flow ◽  
Shear Layer ◽  
Reynolds Numbers ◽  
Complex Problem ◽  
New Method ◽  
Vorticity Field ◽  
High Reynolds Numbers ◽  
Acoustic Sources ◽  
High Reynolds ◽  
Vortex Definition

Vortex or eddy identification is still a complex problem from both the experimental and the theoretical standpoints. The different intuitive and mathematical criteria used to identify vortices are reviewed and observations are made about the weaknesses of most of the criteria. Jeong & Hussain [10] define a new method based on a mathematical criterion. We propose improving this method to yield a simple, accurate and suitable vortex definition. It is successfully applied to an unstable shear layer over a cavity in a pipe. In addition, a link between the vortex criterion and acoustic sources as defined by Lighthill is emphasized.

The Kolmogorov spectrum and its oceanic cousins: a review

1991 ◽  
Vol 434 (1890) ◽  
pp. 125-138 ◽  
Keyword(s):  
Internal Waves ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Constant Density ◽  
Spectral Measurements ◽  
Local Isotropy ◽  
High Reynolds Numbers ◽  
Temperature Spectra ◽  
High Reynolds ◽  
Dissipation Range

Kolmogorov’s theory of turbulence in an incompressible fluid of constant density at high Reynolds numbers has provided a cornerstone for the interpretation of oceanic spectral measurements of turbulence. The most convincing verification of the theory came from observations by Grant, Stewart and Moilliet under conditions that clearly satisfy the basic premises of the theory, but subsequent measurements have explored the influence of ambient stratification and shear on both the energy and temperature spectra. As the turbulence decays, the larger scales of motion interact more weakly as do internal waves, so that Kolmogorov’s cascade becomes disrupted. It has long been known that the existence of a k -5/3 region in the spectrum does not require local isotropy and it is indicated that the success of Kolmogorov scaling in collapsing measured spectra in the dissipation range, does not require a continuing energy cascade from larger scales. Several questions remain unresolved, particularly the reasons for the shape of temperature spectra that have been measured in turbulence generated by large-scale internal waves in a tidal channel.

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