Reynolds-number effects on the structure of a turbulent channel flow

Wei, Tao; Willmarth, William W.

doi:10.1017/s0022112089001667

Cited by 390 publications

(268 citation statements)

References 28 publications

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“…7͑a͔͒, both with and without de-aliasing, show good agreement with the reference data, in this case experimental data by Wei and Willmarth. 33,34 The comparison with case 6 ͑no model, same grid resolution͒ shows the large influence of the model at this Reynolds number. The agreement of the LES estimates for the total rms velocities with the experimental data is not as good as for the mean velocities.…”

Section: Mean and Rms Quantities For Re ä1017mentioning

confidence: 92%

A physical-space version of the stretched-vortex subgrid-stress model for large-eddy simulation

2000

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A physical-space version of the stretched-vortex subgrid-stress model is presented and applied to large-eddy simulations of incompressible flows. This version estimates the subgrid-kinetic energy required for evaluation of the subgrid-stress tensor using local second-order structure-function information of the resolved velocity field at separations of order the local cell size. A relation between the structure function and the energy spectrum is derived using the kinematic assumptions of the stretched-vortex model for locally homogeneous anisotropic turbulence. Results of large-eddy simulations using this model are compared to experimental and direct numerical simulation data. Comparisons are shown for the decay of kinetic energy and energy spectra of decaying isotropic turbulence and for mean velocities, root-mean-square velocity fluctuations and turbulence-kinetic energy balances of channel flow at three different Reynolds numbers.

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Section: Mean and Rms Quantities For Re ä1017mentioning

confidence: 92%

A physical-space version of the stretched-vortex subgrid-stress model for large-eddy simulation

2000

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“…In fully developed turbulent flows all fluctuating velocities scale with u, (for recent reflections on this inner scaling, see e.g. [1,2]). …”

Section: The Velocity Profilementioning

confidence: 99%

Nonlocal stochastic mixing-length theory and the velocity profile in the turbulent boundary layer

Dekker

Leeuw²,

Brink

1995

Physica A: Statistical Mechanics and its Applications

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Nonlocal stochastic mixing-length theory and the velocity profile in the turbulent boundary layer Dekker, H.; de Leeuw, G.; Maassen van den Brin, A. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractTurbulence mixing by finite size eddies will be treated by means of a novel formulation of nonlocal K-theory, involving sample paths and a stochastic closure hypothesis, which implies a well defined recipe for the calculation of sampling and transition rates. The connection with the general theory of stochastic processes will be established. The relation with other nonlocal turbulence models (e.g. transilience and spectral diffusivity theory) is also discussed. Using an analytical sampling rate model (satisfying exchange) the theory is applied to the boundary layer (using a scaling hypothesis), which maps boundary layer turbulence mixing of scalar densities onto a nondiffusive (Kubo-Anderson or kangaroo) type stochastic process. The resulting transport equation for longitudinal momentum Px = ptJ is solved for a unified description of both the inertial and the viscous sublayer including the crossover. With a scaling exponent ~ 0.58 (while local turbulence would amount to s ~ oo) the velocity profile U+ =f(y+) is found to be in excellent agreement with the experimental data. Inter alia (i) the significance of e as a turbulence Cantor set dimension, (ii) the value of the integration constant in the logarithmic region (i.e. if y+ --* oo), (iii) linear timescaling, and (iv) finite Reynolds number effects will be investigated. The (analytical) predictions of the theory for near-wall behaviour (i.e. if y+ ~ 0) of fluctuating quantities also perfectly agree with recent direct numerical simulations. Introduction The velocity profileDimensional analysis of simple shear flow along an infinitely extended smooth surface immediately yields that the nondimensional mean velocity U+ = t J/u, (in the x-direction) must be a function of y+ = u,y/v, where u, is a reference (friction) velocity, y is the distance from the surface, and v is the kinematic viscosity. The friction * Corresponding author. Dekker et al./ Physica A 218 (1995) velocity is defined by means of the total stress z = pu2, in the boundary layer (p being the fluid mass density). In fully developed turbulent fl...

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“…As the aim of this part of the work is to assess the magnitude of the influences of the turbulent velocity fluctuations, the Reynolds-number dependence of the fluctuating quantities is disregarded. This assumption is expected to lead to an underestimation of the streamwise fluctuations and a (smaller) overestimation of the wall-normal fluctuations, as shown by Wei and Willmarth [3]. The use of RMS property correlations obtained at a fixed bulk Reynolds number will thus tend to produce conservative estimates.…”

Section: Methodsmentioning

confidence: 99%

“…This process forms the basis for the selective catalytic and non-catalytic reduction of nitrogen oxides (NO x ) using urea (urea-SCR and urea-SNCR), which are common methods to regulate the emissions of NO x from combustion processes onboard vehicles and in power plants. The primary aim is here to mix ammonia (NH 3 ) with the exhaust gases so that the NH 3 may react efficiently with the NO x . Because of safety issues, a urea-water solution is often preferred to pure NH 3 , as urea will form the NH 3 needed when undergoing thermolysis.…”

Section: Introductionmentioning

confidence: 99%

“…The primary aim is here to mix ammonia (NH 3 ) with the exhaust gases so that the NH 3 may react efficiently with the NO x . Because of safety issues, a urea-water solution is often preferred to pure NH 3 , as urea will form the NH 3 needed when undergoing thermolysis. Consequently, the task of optimizing urea-SCR and SNCR system implies ensuring fast and efficient mixing and heating of the urea-water spray with the hot exhaust gases.…”

Section: Introductionmentioning

confidence: 99%

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The effect of turbulent velocity fluctuations on the convective heat transfer to droplets subjected to evaporation and thermolysis

Guo¹,

Finnerman²,

Ström³

2016

AIP Conference Proceedings

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Abstract. The effect of turbulent velocity fluctuations on the convective heat transfer to single droplets in a turbulent channel flow are investigated numerically. It is found that for properties relevant to typical liquid spray applications, the convective heat transfer is enhanced with increasing droplet size and bulk Reynolds number. The combined effect of convective heat transfer enhancement and increased driving forces for heat and mass transfer due to droplet dispersion is thereafter investigated for a commercial spray application. The probability distribution functions of droplet properties in the spray are found to be significantly affected by the presence of turbulent velocity fluctuations in the carrier phase.

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Reynolds-number effects on the structure of a turbulent channel flow

Cited by 390 publications

References 28 publications

A physical-space version of the stretched-vortex subgrid-stress model for large-eddy simulation

A physical-space version of the stretched-vortex subgrid-stress model for large-eddy simulation

Nonlocal stochastic mixing-length theory and the velocity profile in the turbulent boundary layer

The effect of turbulent velocity fluctuations on the convective heat transfer to droplets subjected to evaporation and thermolysis

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