Vorticity, defects and correlations in active turbulence.

Active and passive fields face to face

The statistical properties of active and passive scalar fields transported by the same turbulent flow are investigated. Four examples of active scalar have been considered: temperature in thermal convection, magnetic potential in two-dimensional magnetohydrodynamics, vorticity in two-dimensional Ekman turbulence and potential temperature in surface flows. In the cases of temperature and vortici...

Characteristics of Momentum Sources and Sinks in Turbulent Channel Flow

The wall-normal gradient of Reynolds shear stress, denoted ∂T+/∂y+, may be thought of as a momentum source or sink term (depending on its sign). This quantity represents a critical driver of the dynamics of wall-turbulence that give rise to the mean velocity distribution. While there have been a number of studies concerning the statistics of ∂T+/∂y+, there remains much to discover regarding the...

The Structure of the Vorticity Field in Turbulent Channel Flow Part 1 : Analysis of Instantaneous Fields and Statistical Correlations

On the Breaking of Mirror Symmetry in Homogeneous Isotropic Turbulence-Helicity Effect

In homogeneous isotropic turbulence when reflexional (or mirror) symmetry breaks down, it becomes necessary to take accounts of the additional fundamental invariants in constructing forms for correlation tensors of different orders that characterize the flow. It is helicity which plays its role in such a situation. Attention is paid here, in particular to the construction of appropriate invaria...

A Vorticity-magnetic Field Dynamo Instability

We generalize the mean field magnetic dynamo to include local evolution of the mean vorticity in addition to the mean magnetic field. The coupled equations exhibit a general mean field dynamo instability that enables the transfer of turbulent energy to the magnetic field and vorticity on larger scales. The growth of the vorticity and magnetic field both require helical turbulence which can be s...