Large-Scale Vortex Instability in Helical Convective Turbulence
Various structures that can be observed in convective flows have recently become a subject of active research (see, e.g., Westfried and Zaleski, 1984). Convection has turned into a sort of laboratory for investigation of structures and structural transitions. Here we discuss a new principal possibility typical of the turbulent convection with non-vanishing mean helicity, i.e. with non-vanishing correlation <v·∇×v> ≠ 0. We show that in turbulent convection there exists a new type of instability that leads to generation of large-scale vortex structures with non-trivial topology of streamlines (see also Moiseev et al., 1988). Such structures can be called topological solitons. Below we consider a simplified version of the problem which, however, preserves all principal physical characteristics of this phenomenon. We consider the helical turbulence created by a random external force and weak deviations from linearity in equations of motion. From physical point of view, non-zero helicity means that turbulence is non-invariant with respect to reflec-tion, i.e. the number of vortices with right-handed screwedness is not equal to the number of vortices with the left-handed one. This is the case when the random external force Fi is an axial vector.
Unable to display preview. Download preview PDF.
- Westfreid, J.E.. and Zaleski. S. (eds.), 1984. “Cellular Structures in Instabilities. Lecture Notes in Physics, v. 210”, Springer-Verlag, Berlin.Google Scholar
- Moiseev, S.S., Rutkevich, P.B., Tur, A.V., and Yanovskii, V.V., 1988, Vortex Dynamo in a Convective medium with Helical Turbulence. Sov. Phys. JEW, 67 (2): 294.Google Scholar
- Monin, A.S.. and Yaglom, A.m., 1975, “Statistical Fluid mechanics”, v. 2, Cambridge, mass., mIT Press.Google Scholar
- Chandrasekhar, S., 1981, “Hydrodynamic and Hydromagnetic Stability”, Dover.Google Scholar
- Gershuni. C.Z., and Zhukhovitskii. E.m., 1976. “Convective Stability of Incompressible Fluids”, keter PublishingHouse, Jerusalem.Google Scholar