Turbulence Modeling and Compressibility.

Compressibility in solar wind plasma turbulence.

Incompressible magnetohydrodynamics is often assumed to describe solar wind turbulence. We use extended self-similarity to reveal scaling in the structure functions of density fluctuations in the solar wind. The obtained scaling is then compared with that found in the inertial range of quantities identified as passive scalars in other turbulent systems. We find that these are not coincident. Th...

Weak compressibility of surface wave turbulence

We study the growth of small-scale inhomogeneities of the density of particles floating in weakly nonlinear, small-amplitude, surface waves. Despite the amplitude smallness, the accumulated effect of the long-time evolution may produce strongly inhomogeneous distribution of the floaters: density fluctuations grow exponentially with a small but finite exponent. We show that the exponent is of si...

Compressibility effects on the scalar mixing in reacting homogeneous turbulence

The compressibility and heat of reaction influence on the scalar mixing in decaying isotropic turbulence and homogeneous shear flow are examined via data generated by direct numerical simulations (DNS). The reaction is modeled as one-step, exothermic, irreversible and Arrhenius type. For the shear flow simulations, the scalar dissipation rate, as well as the time scale ratio of mechanical to sc...

Compressibility effects on turbulence structures of axisymmetric mixing layers

A real-time flow visualization system that produces 17 images over a time span of 150 ms is used to visualize the mixing layers of Mach 1.3 (M c50.59) and Mach 2.0 (M c50.87) ideally expanded high Reynolds number axisymmetric jets. These image sequences reveal details about the influence of compressibility on the dynamics of turbulence structures. In general, the behavior observed in axisymmetr...

Turbulence Modeling