DNS Study of Transitional Channel Flow Accompanied by Turbulent-Stripe Structures

2010 ◽  
Author(s):  
Shizuma Kaneko ◽  
Takahiro Tsukahara ◽  
Yasuo Kawaguchi
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Transport Process ◽  
Energy Transport ◽  
Fluid Motion ◽  
Turbulent Energy ◽  
Regular Pattern ◽  
Plane Poiseuille Flow ◽  
Reynolds Stresses ◽  
Turbulent Region

A regular pattern of turbulent and quasi-laminar fluid motion is known to appear in plane Poiseuille flow near the lowest Reynolds number for which turbulence can be sustained. We focused on this transitional structure called the turbulent stripe and investigated its energy transport process, using a direct numerical simulation. We obtained the budget for Reynolds stresses including v′w′ and w′u′. The spatial outline of the energy transport with respect to the turbulent stripe is proposed. The turbulent energy is produced in both the turbulent region and the quasi-laminar region, and the energy transfer between these two regions is found to be small.

Direct Numerical Simulation of a Fully Developed Turbulent Channel Flow With Respect to the Reynolds Number Dependence

2001 ◽  
Vol 123 (2) ◽  
pp. 382-393 ◽  
Author(s):  
Hiroyuki Abe ◽  
Hiroshi Kawamura ◽  
Yuichi Matsuo
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Correlation Coefficients ◽  
Turbulent Channel Flow ◽  
Reynolds Numbers ◽  
Reynolds Stresses ◽  
Point Correlation ◽  
Reynolds Number Dependence

Direct numerical simulation (DNS) of a fully developed turbulent channel flow for various Reynolds numbers has been carried out to investigate the Reynolds number dependence. The Reynolds number is set to be Reτ=180, 395, and 640, where Reτ is the Reynolds number based on the friction velocity and the channel half width. The computation has been executed with the use of the finite difference method. Various turbulence statistics such as turbulence intensities, vorticity fluctuations, Reynolds stresses, their budget terms, two-point correlation coefficients, and energy spectra are obtained and discussed. The present results are compared with the ones of the DNSs for the turbulent boundary layer and the plane turbulent Poiseuille flow and the experiments for the channel flow. The closure models are also tested using the present results for the dissipation rate of the Reynolds normal stresses. In addition, the instantaneous flow field is visualized in order to examine the Reynolds number dependence for the quasi-coherent structures such as the vortices and streaks.

scholarly journals The dissipation tensor in wall turbulence

2016 ◽  
Vol 807 ◽  
pp. 386-418 ◽  
Author(s):  
G. A. Gerolymos ◽  
I. Vallet
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Plane Channel ◽  
Transport Equations ◽  
Wall Turbulence ◽  
Reynolds Stresses ◽  
Turbulent Plane ◽  
Plane Channel Flow ◽  
Derivatives Of

The paper investigates the dissipation tensor$\unicode[STIX]{x1D700}_{ij}$in wall turbulence. Available direct numerical simulation (DNS) data are examined to illustrate the differences in the anisotropy of the dissipation tensor$\unicode[STIX]{x1D700}_{ij}$with respect to the anisotropy of the Reynolds stresses$\unicode[STIX]{x1D633}_{ij}$. The budgets of the transport equations of the dissipation tensor$\unicode[STIX]{x1D700}_{ij}$are studied using novel DNS data of low Reynolds number turbulent plane channel flow with spatial resolution sufficiently fine to accurately determine the correlations of products of two-derivatives of fluctuating velocities$u_{i}^{\prime }$and pressure$p^{\prime }$which appear in various terms. Finally, the influence of the Reynolds number on the diagonal components of$\unicode[STIX]{x1D700}_{ij}$($\unicode[STIX]{x1D700}_{xx}$,$\unicode[STIX]{x1D700}_{yy}$,$\unicode[STIX]{x1D700}_{zz}$) and on the various terms in their transport equations is studied using available DNS data of Vreman and Kuerten (Phys. Fluids, vol. 26, 2014b, 085103).

scholarly journals The Turbulent Flow over the BARC Rectangular Cylinder: A DNS Study

2021 ◽  
Author(s):  
Alessandro Chiarini ◽  
Maurizio Quadrio
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Finite Differences ◽  
Turbulence Models ◽  
Fine Tuning ◽  
Rectangular Cylinder ◽  
Budget Equation ◽  
Complete Set ◽  
First Time

AbstractA direct numerical simulation (DNS) of the incompressible flow around a rectangular cylinder with chord-to-thickness ratio 5:1 (also known as the BARC benchmark) is presented. The work replicates the first DNS of this kind recently presented by Cimarelli et al. (J Wind Eng Ind Aerodyn 174:39–495, 2018), and intends to contribute to a solid numerical benchmark, albeit at a relatively low value of the Reynolds number. The study differentiates from previous work by using an in-house finite-differences solver instead of the finite-volumes toolbox OpenFOAM, and by employing finer spatial discretization and longer temporal average. The main features of the flow are described, and quantitative differences with the existing results are highlighted. The complete set of terms appearing in the budget equation for the components of the Reynolds stress tensor is provided for the first time. The different regions of the flow where production, redistribution and dissipation of each component take place are identified, and the anisotropic and inhomogeneous nature of the flow is discussed. Such information is valuable for the verification and fine-tuning of turbulence models in this complex separating and reattaching flow.

scholarly journals Fibre-induced drag reduction

2008 ◽  
Vol 602 ◽  
pp. 209-218 ◽  
Author(s):  
J. J. J. GILLISSEN ◽  
B. J. BOERSMA ◽  
P. H. MORTENSEN ◽  
H. I. ANDERSSON
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Reduction ◽  
Elastic Layer ◽  
Turbulent Drag Reduction ◽  
Rigid Polymer ◽  
Fibre Concentration ◽  
Induced Drag ◽  
Turbulent Drag

We use direct numerical simulation to study turbulent drag reduction by rigid polymer additives, referred to as fibres. The simulations agree with experimental data from the literature in terms of friction factor dependence on Reynolds number and fibre concentration. An expression for drag reduction is derived by adopting the concept of the elastic layer.

Numerical Simulation on the Regular Pattern of the Lateral Friction Transmission of the Pile in the Incline under the Pulling Force

2014 ◽  
Vol 501-504 ◽  
pp. 248-253
Author(s):  
Liu Yong Cheng ◽  
Shan Xiong Chen ◽  
Xi Chang Xu ◽  
Xiao Jie Chu ◽  
Tong Bing Lei
Keyword(s):  
Numerical Simulation ◽  
Bearing Capacity ◽  
Pile Foundation ◽  
Influence Factors ◽  
Great Influence ◽  
Regular Pattern ◽  
Slope Gradient ◽  
Pulling Force ◽  
Lateral Friction

The regular pattern of the lateral friction transmission is one of the most critical influences on the ultimate uplift bearing capacity. The pile foundation in the incline under the pulling force has a wide variety of characteristics which is different with the normal pile. Numerical simulation is done by the use of FLAC3D in this paper. The regular pattern of the lateral friction transmission of the pile in the incline under the pulling force is studied. And the influence factors on the lateral friction transmission such as the slope gradient, the length and location of piles are discussed. The results show that the incline has a great influence on the lateral friction transmission. The lateral friction which is away from the incline-side is about 30% to 50% bigger than the incline-side. The slope gradient and the location of piles all have a great influence on the lateral friction transmission.

scholarly journals Effects of Turbulent Reynolds Number on the Performance of Algebraic Flame Surface Density Models for Large Eddy Simulation in the Thin Reaction Zones Regime: A Direct Numerical Simulation Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mohit Katragadda ◽  
Nilanjan Chakraborty ◽  
R. S. Cant
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Fractal Dimension ◽  
Direct Numerical Simulation ◽  
Surface Density ◽  
Flame Surface ◽  
Algebraic Models ◽  
Flame Surface Density ◽  
Turbulent Reynolds Number ◽  
Reaction Zones

A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame surface density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Rethas been varied by modifying the Karlovitz number Ka and the Damköhler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Retand Ka before reaching an asymptotic value for large values of Retand Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thicknessηi/δzdoes not exhibit any significant dependence on Retfor the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.

Study of the Mixed Convection in a Horizontal Channel Heated from below

2015 ◽  
Vol 789-790 ◽  
pp. 398-402
Author(s):  
N. Mahfoud Sahraoui ◽  
Samir Houat ◽  
Nawal Saidi
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Lattice Boltzmann ◽  
Thermal Field ◽  
Lattice Boltzmann Model ◽  
Horizontal Channel ◽  
Comparison Of The Results ◽  
Stretching Ratio ◽  
Boltzmann Model

In this work, a contribution to the modeling and numerical simulation of mixed convection in a horizontal channel heated from below is presented. The lattice Boltzmann model with double thermal populations (TLBM) is used with the D2Q9 model for the dynamic field and D2Q5 for the thermal field. A comparison of the results obtained by the lattice Boltzmann model with those of the literature is presented for an area stretching ratio B = H / L = 20, a Reynolds number Re = 10, Rayleigh Ra = 104 and Peclet number Pe = 20/3. The streamlines and isotherms are presented for different periods of flow.

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