Intermediate Scaling of Turbulent Momentum and Heat Transfer in a Transitional Rough Channel

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Abu Seena ◽  
Noor Afzal
Keyword(s):  
Surface Roughness ◽  
Channel Flow ◽  
Intermediate Layer ◽  
Reynolds Shear Stress ◽  
Strong Support ◽  
Turbulent Channel Flow ◽  
Quality Data ◽  
Order Effects ◽  
Scaling Properties ◽  
Turbulent Wall

The properties of the mean momentum and thermal balance in fully developed turbulent channel flow on transitional rough surface have been explored by method of matched asymptotic expansions. Available high quality data support a dynamically relevant three-layer description that is a departure from two-layer traditional description of turbulent wall flows. The scaling properties of the intermediate layer are determined. The analysis shows the existence of an intermediate layer, with its own characteristic of mesolayer scaling, between the traditional inner and outer layers. Our predictions of the peak values of the Reynolds shear stress and Reynolds heat flux and their locations in the intermediate layer are well supported by the experimental and direct numerical simulation (DNS) data. The inflectional surface roughness data in a turbulent channel flow provide strong support to our proposed universal log law in the intermediate layer, that is, explicitly independent transitional surface roughness. There is no universality of scalings in traditional variables and different expressions are needed for various types of roughness, as suggested, for example, with inflectional type roughness, Colebrook–Moody monotonic roughness, etc. In traditional variables, the roughness scale for inflectional roughness is supported very well by experimental and DNS data. The higher order effects are also presented, which show the implications of the low Reynolds-number flows, where the intermediate layer provides the uniformly valid solutions in terms of generalized logarithmic laws for the velocity and the temperature distributions.

Logarithmic Expansions for Reynolds Shear Stress and Reynolds Heat Flux in a Turbulent Channel Flow

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
Abu Seena ◽  
A. Bushra ◽  
Noor Afzal
Keyword(s):  
Heat Flux ◽  
Shear Stress ◽  
Channel Flow ◽  
Intermediate Layer ◽  
Reynolds Shear Stress ◽  
Turbulent Channel Flow ◽  
Closure Models ◽  
Fully Developed Turbulent Flow ◽  
Logarithmic Functions ◽  
Heat And Fluid Flow

The heat and fluid flow in a fully developed turbulent channel flow have been investigated. The closure model of Reynolds shear stress and Reynolds heat flux as a function of a series of logarithmic functions in the mesolayer variable have been adopted. The interaction between inner and outer layers in the mesolayer (intermediate layer) arising from the balance of viscous effect, pressure gradient and Reynolds shear stress (containing the maxima of Reynolds shear stress) was first proposed by Afzal (1982, “Fully Developed Turbulent Flow in a Pipe: An Intermediate Layer,” Arch. Appl. Mech., 53, 355–377). The unknown constants in the closure models for Reynolds shear stress and Reynolds heat flux have been estimated from the prescribed boundary conditions near the axis and surface of channel. The predictions are compared with the DNS data Iwamoto et al. and Abe et al. for Reynolds shear stress and velocity profile and Abe et al. data of Reynolds heat flux and temperature profile. The limitations of the closure models are presented.

Direct numerical simulation of a turbulent channel flow by an improved vortex in cell method

2013 ◽  
Vol 24 (1) ◽  
pp. 103-123 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Yutaro Yoshii ◽  
Hirotaka Hamada
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Channel Flow ◽  
Staggered Grid ◽  
Wall Region ◽  
Content Type ◽  
The Mean

Purpose – This study is concerned with the direct numerical simulation (DNS) of a turbulent channel flow by an improved vortex in cell (VIC) method. The paper aims to discuss these issues. Design/methodology/approach – First, two improvements for VIC method are proposed to heighten the numerical accuracy and efficiency. A discretization method employing a staggered grid is presented to ensure the consistency among the discretized equations as well as to prevent the numerical oscillation of the solution. A correction method for vorticity is also proposed to compute the vorticity field satisfying the solenoidal condition. Second, the DNS for a turbulent channel flow is conducted by the improved VIC method. The Reynolds number based on the friction velocity and the channel half width is 180. Findings – It is highlighted that the simulated turbulence statistics, such as the mean velocity, the Reynolds shear stress and the budget of the mean enstrophy, agree well with the existing DNS results. It is also shown that the organized flow structures in the near-wall region, such as the streaks and the streamwise vortices, are favourably captured. These demonstrate the high applicability of the improved VIC method to the DNS for wall turbulent flows. Originality/value – This study enables the VIC method to perform the DNS for wall turbulent flows.

Effects of Surfactant Additives on Flow Characteristics at Different Wall-Normal Locations in Turbulent Channel Flow

2016 ◽  
Author(s):  
Lu Wang ◽  
Zhi-Ying Zheng ◽  
Ping-An Liu ◽  
Yue Wang ◽  
Wei-Hua Cai ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Channel Flow ◽  
Viscoelastic Fluid ◽  
Reynolds Shear Stress ◽  
Scaling Law ◽  
Flow Characteristics ◽  
Turbulent Channel Flow ◽  
Flow Properties ◽  
Substrate Layer ◽  
Turbulent Drag

Large eddy simulation (LES) was performed for turbulent channel flow with and without surfactant additives at Reτ = 590. Since turbulent channel flow can be divided into linear substrate layer, buffer layer, logarithm layer and outer layer along the wall-normal direction, so study on the flow properties at different layers in turbulent channel flow of viscoelastic fluid is significant for investigating turbulent drag-reducing mechanism and realizing the control of turbulent drag-reducing flow in the future. In this present work, the influences of surfactant additives on flow properties at different y locations were analyzed by researching the mean streamwise velocity, the root-mean-square velocity fluctuations, Reynolds shear stress and the contributions of different parts to turbulent kinetic energy, as well as the scaling law for four layers by two-dimensional wavelet transform. From the viewpoint of the above results, it is showed that the buffer layer tends to get wider in viscoelastic fluid and it is also demonstrated that viscoelastic effect mainly inhibits the coherent structures in the buffer layer, which are ejected from the linear substrate layer.

Deformation of a compliant wall in a turbulent channel flow

2017 ◽  
Vol 823 ◽  
pp. 345-390 ◽  
Author(s):  
Cao Zhang ◽  
Jin Wang ◽  
William Blake ◽  
Joseph Katz
Keyword(s):  
Channel Flow ◽  
Surface Deformation ◽  
Reynolds Shear Stress ◽  
Pressure Fluctuations ◽  
Turbulent Channel Flow ◽  
Positive Pressure ◽  
Channel Height ◽  
Phase Lag ◽  
Frequency Spectra ◽  
Compliant Wall

Interaction of a compliant wall with a turbulent channel flow is investigated experimentally by simultaneously measuring the time-resolved, three-dimensional (3D) flow field and the two-dimensional (2D) surface deformation. The optical set-up integrates tomographic particle image velocimetry to measure the flow with Mach–Zehnder interferometry to map the deformation. The Reynolds number is $Re_{\unicode[STIX]{x1D70F}}=2300$, and the Young’s modulus of the wall is 0.93 MPa, resulting in a ratio of shear speed to the centreline velocity ($U_{0}$) of 6.8. The wavenumber–frequency spectra of deformation show the surface motions consist of a non-advected low-frequency component and advected modes, some travelling downstream at approximately $U_{0}$ and others at ${\sim}0.72U_{0}$. The r.m.s. values of the advected and non-advected modes are $0.04~\unicode[STIX]{x03BC}\text{m}$$(0.004\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}})$ and $0.2~\unicode[STIX]{x03BC}\text{m}$ ($0.02\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}$), respectively, much smaller than the wall unit ($\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}$), hence they do not affect the flow. Trends in the wall dynamics are elucidated by correlating the deformation with flow variables, including the 3D pressure distribution calculated by spatially integrating the material acceleration. Predictions by the Chase [J. Acoust. Soc. Am., vol. 89 (6), pp. 2589–2596] linear model are also calculated and compared to the measured trends. The spatial deformation–pressure correlations peak at $y/h\approx 0.12$ ($h$ is half channel height), the elevation of Reynolds shear stress maximum in the log-layer. Streamwise lagging of the deformation behind the pressure is caused in part by phase lag of the pressure with decreasing distance from the wall, and in part by material damping. Positive deformations (bumps) caused by negative pressure fluctuations are preferentially associated with ejections involving spanwise vortices located downstream and quasi-streamwise vortices with spanwise offset. Results of conditional correlations are consistent with the presence of hairpin-like structures. The negative deformations (dimples) are preferentially associated with positive pressure fluctuations at the transition between an upstream sweep to a downstream ejection.

Fluid particle dynamics and the non-local origin of the Reynolds shear stress

2018 ◽  
Vol 847 ◽  
pp. 520-551 ◽  
Author(s):  
Peter S. Bernard ◽  
Martin A. Erinin
Keyword(s):  
Shear Stress ◽  
Channel Flow ◽  
Reynolds Shear Stress ◽  
Mixing Time ◽  
Turbulent Channel Flow ◽  
Structural Features ◽  
Fluid Particle ◽  
Normal Velocity ◽  
Mean Velocity ◽  
Non Local

The causative factors leading to the Reynolds shear stress distribution in turbulent channel flow are analysed via a backward particle path analysis. It is found that the classical displacement transport mechanism, by which changes in the mean velocity field over a mixing time correlate with the wall-normal velocity, is the dominant source of Reynolds shear stress. Approximately 20 % of channel flow at any given time contains fluid motions that contribute to displacement transport. Much rarer events provide a small but non-negligible contribution to the Reynolds shear stress due to fluid particle accelerations and long-lived correlations deriving from structural features of the near-wall flow. The Reynolds shear stress in channel flow is shown to be a non-local phenomenon that is not conducive to description via a local model and particularly one depending directly on the local mean velocity gradient.

Direct numerical simulation of turbulent channel flow with permeable walls

2002 ◽  
Vol 450 ◽  
pp. 259-285 ◽  
Author(s):  
SEONGHYEON HAHN ◽  
JONGDOO JE ◽  
HAECHEON CHOI
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Channel Flow ◽  
Permeable Wall ◽  
Brinkman Equation ◽  
Navier Stokes Equation ◽  
Permeable Walls

The main objectives of this study are to suggest a proper boundary condition at the interface between a permeable block and turbulent channel flow and to investigate the characteristics of turbulent channel flow with permeable walls. The boundary condition suggested is an extended version of that applied to laminar channel flow by Beavers & Joseph (1967) and describes the behaviour of slip velocities in the streamwise and spanwise directions at the interface between the permeable block and turbulent channel flow. With the proposed boundary condition, direct numerical simulations of turbulent channel flow that is bounded by the permeable wall are performed and significant skin-friction reductions at the permeable wall are obtained with modification of overall flow structures. The viscous sublayer thickness is decreased and the near-wall vortical structures are significantly weakened by the permeable wall. The permeable wall also reduces the turbulence intensities, Reynolds shear stress, and pressure and vorticity fluctuations throughout the channel except very near the wall. The increase of some turbulence quantities there is due to the slip-velocity fluctuations at the wall. The boundary condition proposed for the permeable wall is validated by comparing solutions with those obtained from a separate direct numerical simulation using both the Brinkman equation for the interior of a permeable block and the Navier–Stokes equation for the main channel bounded by a permeable block.

scholarly journals Optimal bursts in turbulent channel flow

2017 ◽  
Vol 817 ◽  
pp. 35-60 ◽  
Author(s):  
Mirko Farano ◽  
Stefania Cherubini ◽  
Jean-Christophe Robinet ◽  
Pietro De Palma
Keyword(s):  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Reynolds Numbers ◽  
High Amplitude ◽  
Optimization Strategy ◽  
Hairpin Vortices ◽  
Bursting Events ◽  
Turbulent Wall ◽  
Spatial Spectra

Bursts are recurrent, transient, highly energetic events characterized by localized variations of velocity and vorticity in turbulent wall-bounded flows. In this work, a nonlinear energy optimization strategy is employed to investigate whether the origin of such bursting events in a turbulent channel flow can be related to the presence of high-amplitude coherent structures. The results show that bursting events correspond to optimal energy flow structures embedded in the fully turbulent flow. In particular, optimal structures inducing energy peaks at short time are initially composed of highly oscillating vortices and streaks near the wall. At moderate friction Reynolds numbers, through the bursts, energy is exchanged between the streaks and packets of hairpin vortices of different sizes reaching the outer scale. Such an optimal flow configuration reproduces well the spatial spectra as well as the probability density function typical of turbulent flows, recovering the mechanism of direct-inverse energy cascade. These results represent an important step towards understanding the dynamics of turbulence at moderate Reynolds numbers and pave the way to new nonlinear techniques to manipulate and control the self-sustained turbulence dynamics.

scholarly journals Large-eddy simulation and wall modelling of turbulent channel flow

2009 ◽  
Vol 631 ◽  
pp. 281-309 ◽  
Author(s):  
D. CHUNG ◽  
D. I. PULLIN
Keyword(s):  
Shear Stress ◽  
Large Eddy Simulation ◽  
Channel Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Wall Region ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Near Wall

We report large-eddy simulation (LES) of turbulent channel flow. This LES neither resolves nor partially resolves the near-wall region. Instead, we develop a special near-wall subgrid-scale (SGS) model based on wall-parallel filtering and wall-normal averaging of the streamwise momentum equation, with an assumption of local inner scaling used to reduce the unsteady term. This gives an ordinary differential equation (ODE) for the wall shear stress at every wall location that is coupled with the LES. An extended form of the stretched-vortex SGS model, which incorporates the production of near-wall Reynolds shear stress due to the winding of streamwise momentum by near-wall attached SGS vortices, then provides a log relation for the streamwise velocity at the top boundary of the near-wall averaged domain. This allows calculation of an instantaneous slip velocity that is then used as a ‘virtual-wall’ boundary condition for the LES. A Kármán-like constant is calculated dynamically as part of the LES. With this closure we perform LES of turbulent channel flow for Reynolds numbers Reτ based on the friction velocity uτ and the channel half-width δ in the range 2 × 103 to 2 × 107. Results, including SGS-extended longitudinal spectra, compare favourably with the direct numerical simulation (DNS) data of Hoyas & Jiménez (2006) at Reτ = 2003 and maintain an O(1) grid dependence on Reτ.

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