TURBULENCE
| Collection | International Encyclopedia of Systems and Cybernetics |
|---|---|
| Year | 2004 |
| Vol. (num.) | 2(2) |
| ID | ◀ 3655 ▶ |
| Object type | Human sciences, Methodology or model |
The irregular motion of a fluid with local randomly fluctuating velocities and pressures.
D. RUELLE (1991, p.70) explains that turbulence appears in fluids to which a source provides growing quantities of energy. In that case, according to L.D. LANDAU, a growing number of flowing modes in the fluid become excited. Turbulence than results of the neighborhood of stable and unstable regions“. Turbulence was more recently described by F. TAKENS and D. RUELLE as a chaotic process that could appear even in a dynamic system with no more than three independent frequencies.
I. SINAI states that, in turbulence: “… the movement is so complex that the notion of individual trajectory loses its sense and the only possible description is in terms of average characteristics”. He moreover connects turbulence with ergodicity: “(in) ergodic theory, the fundamental problem is the analysis of the causes generating the emergence of statistical laws in dynamic systems” (1988, p.69).
At a limit, the movement even escapes from ergodic regularity and turbulence also becomes connected with the study of chaos and chaotic systems. K.DE GREENE states: “In systems evolution chaos and turbulence may well be prerequisite to structural change… Short-term turbulence can be part of long-term evolution toward a new structure”.
DE GREENE applies his views to “societal or ecological transition or transformation (when) perturbation of the environment by human actions may lead to the development of new pockets of order, or new autonomous systems, in the environment” (1990, p.52-53).
All this is coincident with the model of fractalization of vortexes (vortexes within vortexes, within vortexes, etc…).
Turbulence can be intermittent. This happens as stated by M. FARGE: “… when the most active regions are not homogeneously distributed in space and time, but on the contrary appear as turbulent and violent ”puffs“. Spatio-temporal intermittence does lead to questioning the homogeneity and stationary hypothesis basic to the statistical theory of turbulence” (1992, p.239).