scholarly journals Statistics and structure of spanwise rotating turbulent channel flow at moderate Reynolds numbers

2017 ◽  
Vol 828 ◽  
pp. 424-458 ◽  
Author(s):  
Geert Brethouwer
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Large Scale ◽  
Linear Part ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Reynolds Stresses ◽  
System Rotation ◽  
The Mean ◽  
Spanwise Rotation

A study of fully developed plane turbulent channel flow subject to spanwise system rotation through direct numerical simulations is presented. In order to study both the influence of the Reynolds number and spanwise rotation on channel flow, the Reynolds number $Re=U_{b}h/\unicode[STIX]{x1D708}$ is varied from a low 3000 to a moderate 31 600 and the rotation number $Ro=2\unicode[STIX]{x1D6FA}h/U_{b}$ is varied from 0 to 2.7, where $U_{b}$ is the mean bulk velocity, $h$ the channel half-gap, $\unicode[STIX]{x1D708}$ the viscosity and $\unicode[STIX]{x1D6FA}$ the system rotation rate. The mean streamwise velocity profile displays also at higher $Re$ a characteristic linear part with a slope near to $2\unicode[STIX]{x1D6FA}$, and a corresponding linear part in the profiles of the production and dissipation rate of turbulent kinetic energy appears. With increasing $Ro$, a distinct unstable side with large spanwise and wall-normal Reynolds stresses and a stable side with much weaker turbulence develops in the channel. The flow starts to relaminarize on the stable side of the channel and persisting turbulent–laminar patterns appear at higher $Re$. If $Ro$ is further increased, the flow on the stable side becomes laminar-like while at yet higher $Ro$ the whole flow relaminarizes, although the calm periods might be disrupted by repeating bursts of turbulence, as explained by Brethouwer (Phys. Rev. Fluids, vol. 1, 2016, 054404). The influence of the Reynolds number is considerable, in particular on the stable side of the channel where velocity fluctuations are stronger and the flow relaminarizes less quickly at higher $Re$. Visualizations and statistics show that, at $Ro=0.15$ and 0.45, large-scale structures and large counter-rotating streamwise roll cells develop on the unstable side. These become less noticeable and eventually vanish when $Ro$ rises, especially at higher $Re$. At high $Ro$, the largest energetic structures are larger at lower $Re$.

Direct numerical simulation of turbulent channel flow up to

2015 ◽  
Vol 774 ◽  
pp. 395-415 ◽  
Author(s):  
Myoungkyu Lee ◽  
Robert D. Moser
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Mean Velocity ◽  
Layer Structures ◽  
High Reynolds

A direct numerical simulation of incompressible channel flow at a friction Reynolds number ($\mathit{Re}_{{\it\tau}}$) of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant ${\it\kappa}=0.384\pm 0.004$. There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits $k^{-1}$ dependence over a short range in wavenumber $(k)$. Further, consistent with previous experimental observations, when these spectra are multiplied by $k$ (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the $k^{-1}$ range.

scholarly journals Coherent structures in the linearized impulse response of turbulent channel flow

2019 ◽  
Vol 863 ◽  
pp. 1190-1203 ◽  
Author(s):  
Sabarish B. Vadarevu ◽  
Sean Symon ◽  
Simon J. Illingworth ◽  
Ivan Marusic
Keyword(s):  
Channel Flow ◽  
Coherent Structures ◽  
Large Scale ◽  
Body Force ◽  
Stokes Equations ◽  
Turbulent Channel Flow ◽  
Kinetic Energy Density ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Velocity Fluctuations

We study the evolution of velocity fluctuations due to an isolated spatio-temporal impulse using the linearized Navier–Stokes equations. The impulse is introduced as an external body force in incompressible channel flow at $Re_{\unicode[STIX]{x1D70F}}=10\,000$. Velocity fluctuations are defined about the turbulent mean velocity profile. A turbulent eddy viscosity is added to the equations to fix the mean velocity as an exact solution, which also serves to model the dissipative effects of the background turbulence on large-scale fluctuations. An impulsive body force produces flow fields that evolve into coherent structures containing long streamwise velocity streaks that are flanked by quasi-streamwise vortices; some of these impulses produce hairpin vortices. As these vortex–streak structures evolve, they grow in size to be nominally self-similar geometrically with an aspect ratio (streamwise to wall-normal) of approximately 10, while their kinetic energy density decays monotonically. The topology of the vortex–streak structures is not sensitive to the location of the impulse, but is dependent on the direction of the impulsive body force. All of these vortex–streak structures are attached to the wall, and their Reynolds stresses collapse when scaled by distance from the wall, consistent with Townsend’s attached-eddy hypothesis.

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.

Isotropy of the small scales of turbulence at low Reynolds number

1993 ◽  
Vol 251 ◽  
pp. 219-238 ◽  
Author(s):  
J. Kim ◽  
R. A. Antonia
Keyword(s):  
Reynolds Number ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Small Reynolds Number ◽  
Simulation Data ◽  
Local Isotropy ◽  
Streamwise Velocity Fluctuation ◽  
The Mean ◽  
The Relationship ◽  
Mean Strain

Spectral local isotropy tests are applied to direct numerical simulation data, mainly at the centreline of a fully developed turbulent channel flow. Despite the small Reynolds number of the simulation, the high-wavenumber behaviour of velocity and vorticity spectra is consistent with local isotropy. This consistency is verified by the relationship between streamwise wavenumber spectra and spanwise wavenumber spectra. The high-wavenumber behaviour of the pressure spectrum is also consistent with local isotropy and compares favourably with the calculation of Batchelor (1951), which assumes isotropy and joint normality of the velocity field at two points in space. The latter assumption is validated by the shape but not the magnitude of the quadruple correlation of the streamwise velocity fluctuation at small separations. There is only partial support for local spectral isotropy away from the centreline as the magnitude of the mean strain rate increases.

Spatial organization of large- and very-large-scale motions in a turbulent channel flow

2014 ◽  
Vol 749 ◽  
pp. 818-840 ◽  
Author(s):  
Jin Lee ◽  
Jae Hwa Lee ◽  
Jung-Il Choi ◽  
Hyung Jin Sung
Keyword(s):  
Channel Flow ◽  
Large Scale ◽  
Spatial Organization ◽  
Outer Region ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Velocity Fluctuations ◽  
Spatial Features ◽  
Temporal Features ◽  
Low Speed Streaks

AbstractDirect numerical simulations were carried out to investigate the spatial features of large- and very-large-scale motions (LSMs and VLSMs) in a turbulent channel flow ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Re}_{\tau }=930$). A streak detection method based on the streamwise velocity fluctuations was used to individually trace the cores of LSMs and VLSMs. We found that both the LSM and VLSM populations were large. Several of the wall-attached LSMs stretched toward the outer regions of the channel. The VLSMs consisted of inclined outer LSMs and near-wall streaks. The number of outer LSMs increased linearly with the streamwise length of the VLSMs. The temporal features of the low-speed streaks in the outer region revealed that growing and merging events dominated the large-scale (1–$3\delta $) structures. The VLSMs $({>}3\delta )$ were primarily created by merging events, and the statistical analysis of these events supported that the merging of large-scale upstream structures contributed to the formation of VLSMs. Because the local convection velocity is proportional to the streamwise velocity fluctuations, the streamwise-aligned structures of the positive- and negative-$u$ patches suggested a primary mechanism underlying the merging events. The alignment of the positive- and negative-$u$ structures may be an essential prerequisite for the formation of VLSMs.

Very-large-scale fluctuations in turbulent channel flow at low Reynolds number

2016 ◽  
Vol 62 ◽  
pp. 593-597
Author(s):  
Masaharu Matsubara ◽  
Shun Horii ◽  
Yoshiyuki Sagawa ◽  
Yuta Takahashi ◽  
Daisuke Saito
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Large Scale ◽  
Low Reynolds Number ◽  
Turbulent Channel Flow ◽  
Low Reynolds

1519 Large-scale feature in two-dimensional turbulent channel flow in the wide range of Reynolds number

2016 ◽  
Vol 2016.53 (0) ◽  
pp. _1519-1_-_1519-5_
Author(s):  
Shun HORII ◽  
Yoshiyuki SAGAWA ◽  
Daisuke SAITO ◽  
Yuta TAKAHASHI ◽  
Masaharu MATSUBARA
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Large Scale ◽  
Turbulent Channel Flow ◽  
Two Dimensional ◽  
Scale Feature ◽  
Wide Range

On the universality of local dissipation scales in turbulent channel flow

2015 ◽  
Vol 786 ◽  
pp. 234-252 ◽  
Author(s):  
S. C. C. Bailey ◽  
B. M. Witte
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Turbulent Channel Flow ◽  
Reynolds Numbers ◽  
Small Scale ◽  
Length Scale ◽  
Scaling Behaviour ◽  
Sixth Moment

Well-resolved measurements of the small-scale dissipation statistics within turbulent channel flow are reported for a range of Reynolds numbers from $Re_{{\it\tau}}\approx 500$ to 4000. In this flow, the local large-scale Reynolds number based on the longitudinal integral length scale is found to poorly describe the Reynolds number dependence of the small-scale statistics. When a length scale based on Townsend’s attached-eddy hypothesis is used to define the local large-scale Reynolds number, the Reynolds number scaling behaviour was found to be more consistent with that observed in homogeneous, isotropic turbulence. The Reynolds number scaling of the dissipation moments up to the sixth moment was examined and the results were found to be in good agreement with predicted scaling behaviour (Schumacher et al., Proc. Natl Acad. Sci. USA, vol. 111, 2014, pp. 10961–10965). The probability density functions of the local dissipation scales (Yakhot, Physica D, vol. 215 (2), 2006, pp. 166–174) were also determined and, when the revised local large-scale Reynolds number is used for normalization, provide support for the existence of a universal distribution which scales differently for inner and outer regions.

Statistics of Particle Suspensions in Turbulent Channel Flow

2012 ◽  
Vol 11 (4) ◽  
pp. 1311-1322 ◽  
Author(s):  
Lihao Zhao ◽  
Helge I. Andersson
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Particle Concentration ◽  
Response Times ◽  
Turbulent Channel Flow ◽  
Reynolds Numbers ◽  
Channel Height ◽  
Velocity Statistics ◽  
The Mean ◽  
Particle Velocities

AbstractParticle dynamics in a turbulent channel flow is considered. The effects of particle concentration and Reynolds number on the particle velocity statistics are investigated. Four different particle response times, τ+=1, 5, 30 and 100, are examined for three different Reynolds numbers, Re*=200, 360 and 790 (based on channel height and friction velocity). The particle concentration evolves with time and statistics obtained during three different sampling periods might be distinctly different. The mean and fluctuating particle velocities are substantially affected both by the particle response time and by the Reynolds number of the flow.

The structure of the viscous sublayer and the adjacent wall region in a turbulent channel flow

1974 ◽  
Vol 65 (3) ◽  
pp. 439-459 ◽  
Author(s):  
Helmut Eckelmann
Keyword(s):  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Viscous Sublayer ◽  
Wall Region ◽  
Normal Velocity ◽  
Mean Velocity ◽  
Velocity Fluctuations ◽  
Mean Values ◽  
The Mean

Hot-film anemometer measurements have been carried out in a fully developed turbulent channel flow. An oil channel with a thick viscous sublayer was used, which permitted measurements very close to the wall. In the viscous sublayer between y+ ≃ 0·1 and y+ = 5, the streamwise velocity fluctuations decreased at a higher rate than the mean velocity; in the region y+ [lsim ] 0·1, these fluctuations vanished at the same rate as the mean velocity.The streamwise velocity fluctuations u observed in the viscous sublayer and the fluctuations (∂u/∂y)0 of the gradient at the wall were almost identical in form, but the fluctuations of the gradient at the wall were found to lag behind the velocity fluctuations with a lag time proportional to the distance from the wall. Probability density distributions of the streamwise velocity fluctuations were measured. Furthermore, measurements of the skewness and flatness factors made by Kreplin (1973) in the same flow channel are discussed. Measurements of the normal velocity fluctuations v at the wall and of the instantaneous Reynolds stress −ρuv were also made. Periods of quiescence in the − ρuv signal were observed in the viscous sublayer as well as very active periods where ratios of peak to mean values as high as 30:1 occurred.

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