Advances in the Fundamental Aspects of Turbulence: Energy Transfer, Interacting Scales, and Self-Preservation in Isotropic Decay

1998 ◽  
Vol 51 (4) ◽  
pp. 267-301 ◽  
Author(s):  
Ye Zhou ◽  
Charles G. Speziale

The fundamental aspects of isotropic turbulence are reviewed in order to gain a better insight into the physical processes of turbulence. After first reviewing the Kolmogorov energy spectrum and the energy cascade, the Kolmogorov hypothesis of local isotropy is discussed in depth. Then, the detailed physical processes involving energy transfer and interacting scales in isotropic turbulence, including triad interactions, are reviewed. The inertial range and self-similarity are also discussed along with the response of the small scales to large-scale anisotropy and the final stages of the decay process. Results from direct and large-eddy simulations of isotropic turbulence—including a discussion of subgrid scale modeling—are then discussed in detail to illustrate these points. The article closes with a review of self-preservation in isotropic turbulence and a discussion of the prospects for future research. It contains 155 references.

Author(s):  
V. Solovej ◽  
K. Gorbunov ◽  
V. Vereshchak ◽  
O. Gorbunova

A study has been mode of transport-controlled mass transfer-controlled to particles suspended in a stirred vessel. The motion of particle in a fluid was examined and a method of predicting relative velocities in terms of Kolmogoroff’s theory of local isotropic turbulence for mass transfer was outlined. To provide a more concrete visualization of complex wave form of turbulence, the concepts of eddies, of eddy velocity, scale (or wave number) and energy spectrum, have proved convenient. Large scale motions of scale contain almost all of the energy and they are directly responsible for energy diffusion throughout the stirring vessel by kinetic and pressure energies. However, almost no energy is dissipated by the large-scale energy-containing eddies. A scale of motion less than is responsible for convective energy transfer to even smaller eddy sires. At still smaller eddy scales, close to a characteristic microscale, both viscous energy dissipation and convection are the rule. The last range of eddies has been termed the universal equilibrium range. It has been further divided into a low eddy size region, the viscous dissipation subrange, and a larger eddy size region, the inertial convection subrange. Measurements of energy spectrum in mixing vessel are shown that there is a range, where the so called -(5/3) power law is effective. Accordingly, the theory of local isotropy of Kolmogoroff can be applied because existence of the internal subrange. As the integrated value of local energy dissipation rate agrees with the power per unit mass of liquid from the impeller, almost all energy from the impeller is viscous dissipated in eddies of microscale. The correlation for mass transfer to particles suspended in a stirred vessel is recommended. The results of experimental study are approximately 12 % above the predicted values.


2002 ◽  
Vol 455 ◽  
pp. 195-212 ◽  
Author(s):  
DANIELE CARATI ◽  
MICHAEL M. ROGERS ◽  
ALAN A. WRAY

A statistical ensemble of large-eddy simulations (LES) is run simultaneously for the same flow. The information provided by the different large-scale velocity fields is used in an ensemble-averaged version of the dynamic model. This produces local model parameters that only depend on the statistical properties of the flow. An important property of the ensemble-averaged dynamic procedure is that it does not require any spatial averaging and can thus be used in fully inhomogeneous flows. Also, the ensemble of LES provides statistics of the large-scale velocity that can be used for building new models for the subgrid-scale stress tensor. The ensemble-averaged dynamic procedure has been implemented with various models for three flows: decaying isotropic turbulence, forced isotropic turbulence, and the time-developing plane wake. It is found that the results are almost independent of the number of LES in the statistical ensemble provided that the ensemble contains at least 16 realizations.


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