It is the energy cascade that explains the origin of Kolmogorov’s similarity hypothesis. The recent direct numerical simulations have revealed that the energy cascade in developed turbulence is caused by the creation of smaller-scale coherent vortices in straining regions around larger-scale coherent vortices. This concrete picture of the energy cascade in terms of coherent structures, however, denies the local equilibrium hypothesis, which is the basis of the Kolmogorov theory.
In this article, we review recent progresses in the understanding of the transition from laminar flow to turbulence in shear flows. We describe why and how the idea of nonequilibrium phase transition can be applied to these transitions in different flows.
Recently, it has gradually been an interest for the granular community that the typical phenomena well-known in the fluid turbulence systems, such as vortex structure, cascade mechanism and the statistical law of the spatial spectra, were found in the study of typical granular systems. In this review, we focus on these topics from the viewpoint of how the dissipative multi-body dynamics system composed of elements affect the spatiotemporal structure of the macroscopic systems. We address the results of two typical prototype model systems with the novel methodology of molecular dynamics simulation, where the rarified granular gas system and dense granular jamming systems were studied. Finally, we would like to remark the future perspective.
We review the recent research developments of quantum turbulence. Quantum turbulence refers to turbulence in quantum condensed systems like superfluid helium and atomic Bose-Einstein condensates. Hydrodynamics of quantum condensed systems is characterized by the appearance of order parameters, leading to inviscid superflow and topological defects such as quantized vortices. These characteristics make quantum turbulence a prototype of turbulence more easily accessible than conventional one.
Plasma turbulence possesses unique properties different from those of the neutral fluid turbulence, such that it is driven by instabilities with a variety of spatiotemporal scales, is coupled with electromagnetic fluctuations, and generates perturbations of the distribution function on the phase space. The low-frequency turbulence in magnetized plasmas with strong anisotropy is also related to various transport phenomena. Here, we describe the theoretical background with introduction of recent applications to space and fusion plasmas.
Recent observations have revealed that there are various kinds of high energy astrophysical phenomena. They are considered to be high Reynolds number plasma due to their large spatial scale and high temperature, and it is natural to assume those plasma are in a turbulent state. It is expected that turbulence plays an important role in those phenomena, such as dissipation of back ground magnetic field and acceleration of electrons emitting non-thermal photons.
In this article, we explain several recent results of relativistic turbulence researches. Relativistic turbulence usually includes very high velocity close to that of light, and relativistic turbulence research should treat many effects neglected in non-relativistic turbulence. We introduce those results obtained mainly by numerical simulations. In particular, we introduce the recent study of effects from relativistic electromagnetic field, which results in a new strong-coupling regime of relativistic magnetohydrodynamic turbulence.
We focus on turbulence in high-energy astronomical objects and review its excitation mechanism and role in the activity of high-energy phenomena. The excitation process and property of turbulence are still unclear, but turbulence may play an important role in accelerating particles, which emit wide band electromagnetic wave or high-energy neutrinos.