First normal stress difference and crystallization in a dense sheared granular fluid
The first normal stress difference (1) and the microstructure in a dense sheared granular fluid of smooth inelastic hard-disks are probed using event-driven simulations. While the anisotropy in the se...
The first normal stress difference (1) and the microstructure in a dense sheared granular fluid of smooth inelastic hard-disks are probed using event-driven simulations. While the anisotropy in the se...
Velocity-scalar filtered density function for large eddy simulation of turbulent flows
A methodology termed the "velocity-scalar filtered density function" (VSFDF) is developed and implemented for large eddy simulation (LES) of turbulent flows. In this methodology, the effects...
A methodology termed the "velocity-scalar filtered density function" (VSFDF) is developed and implemented for large eddy simulation (LES) of turbulent flows. In this methodology, the effects...
Is the turbulent wind in convective flows driven by fluctuations?
Phys. Fluids 15, 2313 (2003); doi:10.1063/1.1588638
Published 1 July 2003
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In this paper, a direct check is presented whether the turbulent wind in Rayleigh–Bénard convection is driven by turbulent Reynolds stresses, associated with the tilting plumes at the upper and the lower horizontal walls. This is done by evaluation of experimental data obtained from particle image velocimetry measurements in the centerplane of a cubic convection cell and two-dimensional solution of the Navier–Stokes equations in a square domain. Although, in both, there are regions of negative turbulent energy production P = –
uiuj
![[partial-derivative]](http://scitation.aip.org/stockgif2/part.gif)
Ui/xj, meaning that, locally, energy is transferred from velocity fluctuations to the mean flow, the integral of turbulent energy production over the whole flow field is essentially positive. This implies that the turbulent wind is not driven by the turbulent Reynolds stresses. It is demonstrated from the numerical results that once the mean flow is established, the temperature of the fluid is larger at one side wall and smaller at the other and therefore, the mean flow is driven by the mean buoyant force at the side walls. ©2003 American Institute of Physics.
uiujUi/xj, meaning that, locally, energy is transferred from velocity fluctuations to the mean flow, the integral of turbulent energy production over the whole flow field is essentially positive. This implies that the turbulent wind is not driven by the turbulent Reynolds stresses. It is demonstrated from the numerical results that once the mean flow is established, the temperature of the fluid is larger at one side wall and smaller at the other and therefore, the mean flow is driven by the mean buoyant force at the side walls. ©2003 American Institute of Physics.
| History: | Received 22 October 2002; accepted 13 May 2003; published 1 July 2003 |
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REFERENCES (15)
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- Such flow situations are denoted by the term negative eddy viscosity emphasizing that the turbulent transport of momentum occurs against the mean velocity gradient, i.e., from regions with low momentum to regions with high momentum, with concomitant transfer of kinetic energy in the opposite direction too, i.e., from fluctuations to the mean flow. Among other things this means that the mean flow can be driven by turbulent fluctuations as was assumed by Krishnamurti and Howard. Such situations are possible in the presence of some energy supply other than the mean strain and are observed both in laboratory experiments and in large scale flows in geo- and astrophysics (Refs. 10 and 11).
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- A. Tsinober, An Informal Introduction to Turbulence (Kluwer, Berlin, 2001).
- Krishnamurti and Howard (Ref. 13) attempted to make such measurements in a different geometry, in a cylindrical annular tank of fluid uniformly heated below and cooled above. We return to this matter below.
- R. Krishnamurti and L. N. Howard, "Large scale flow in turbulent convection: laboratory experiments and a mathematical model," Papers Meteorological Research, A Journal of the Meteorological Soc. of the Republic of China 6, 143 (1983).
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- T. Elperin, N. Keeorin, I. Rogachevskii, and S. Zilitinkevich, "Formation of large-scale semi-organized structures in turbulent convection," Phys. Rev. E 66, 066305 (2002).
