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.

scholarly journals Simulation of Rotating Channel Flow With Heat Transfer: Evaluation of Closure Models

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Alan S. Hsieh ◽  
Sedat Biringen ◽  
Alec Kucala
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Stress ◽  
Channel Flow ◽  
Turbulence Models ◽  
Turbulent Channel Flow ◽  
Turbulent Heat ◽  
Stress Distributions ◽  
Mean Velocity ◽  
Closure Models

A direct numerical simulation (DNS) of spanwise-rotating turbulent channel flow was conducted for four rotation numbers: Rob=0, 0.2, 0.5, and 0.9 at a Reynolds number of 8000 based on laminar centerline mean velocity and Prandtl number 0.71. The results obtained from these DNS simulations were utilized to evaluate several turbulence closure models for momentum and heat transfer transport in rotating turbulent channel flow. Four nonlinear eddy viscosity turbulence models were tested and among these, explicit algebraic Reynolds stress models (EARSM) obtained the Reynolds stress distributions in best agreement with DNS data for rotational flows. The modeled pressure–strain functions of EARSM were shown to have strong influence on the Reynolds stress distributions near the wall. Turbulent heat flux distributions obtained from two explicit algebraic heat flux models (EAHFM) consistently displayed increasing disagreement with DNS data with increasing rotation rate.

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.

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.

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.

scholarly journals Study on the Drag Reducing Channel Fluids by Experiments and DNS Using Giesekus Model

2014 ◽  
Vol 6 ◽  
pp. 175059 ◽  
Author(s):  
Weiguo Gu ◽  
Dezhong Wang ◽  
Yasuo Kawaguchi
Keyword(s):  
Shear Stress ◽  
Channel Flow ◽  
Mass Concentration ◽  
Reynolds Shear Stress ◽  
Surfactant Solution ◽  
Solution Flow ◽  
Velocity Fluctuations ◽  
Giesekus Model ◽  
Numerical Studies ◽  
Fluid Characteristics

Both experimental and numerical studies are simultaneously performed for fully developed water and surfactant solution channel flow. The comparison aims at the surfactant solution flow in experiment with mass concentration of 25 ppm at Re = 1000 and Giesekus model with Weissenberg numbers of 10 and 40 at Reτ = 150. Big differences are found between the experimental and DNS results by comparing the distributions of velocity fluctuations, Reynolds shear stress, and so on. Although large drag reduction appears in DNS, Giesekus model has some limitations in describing the fluid characteristics and viscoelasticity of the surfactant solution.

Evolution of wall shear stress with Reynolds number in fully developed turbulent channel flow experiments

2019 ◽  
Vol 4 (7) ◽  
Author(s):  
Pierre-Alain Gubian ◽  
Jordan Stoker ◽  
James Medvescek ◽  
Laurent Mydlarski ◽  
B. Rabi Baliga
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Wall Shear ◽  
Flow Experiments

Turbulent Statistics of Rarefield Flows in Microchannel Flow and Heat Transfer

2004 ◽  
Author(s):  
G. X. Li ◽  
W. Q. Tao ◽  
Z. Y. Li ◽  
B. Yu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Wall Region ◽  
Turbulent Heat ◽  
Time Step ◽  
Temperature Variance ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics

Direct numerical simulation has been carried out to investigate the effect of weak rarefaction on turbulent gas flow and heat transfer characteristics in mirochannel. The Reynolds number based on the friction velocity and the channel half width is 150. Grid number is 64×128×64. Fractional time step method is employed for the unsteady Navier-Stokes equations, and the governing equations are discretized with Finite Difference Method. Statistical quantities such as turbulent intensity, Reynolds shear stress, turbulent heat flux and temperature variance are obtained under various Knudsen number from 0 to 0.05. The results show that rarefaction can influence the turbulent flow and heat transfer statistics. The streamwise mean velocity and temperature increase with increase of Kn number. In the near wall region rarefaction can increase the turbulent intensities and temperature variance. The effect of rarefaction on Reynolds shear stress and wall-normal heat flux are presented. The instantaneous velocity fluctuations in the vicinity of the wall are visualized and the influence of Kn number on the flow structure is discussed.

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