The effect of a background rotation on the decay of homogeneous turbulence produced by a grid is experimentally investigated. Experiments have been performed in a channel mounted in the large-scale ’Coriolis’ rotating platform, and measurements have been carried out in the planes normal and parallel to the rotation axis using particle image velocimetry. After a short period of about 0.4 tank ro...

We simulate incompressible, MHD turbulence using a pseudo-spectral code. Our major conclusions are as follows. 1) MHD turbulence is most conveniently described in terms of counter propagating shear Alfvén and slow waves. Shear Alfvén waves control the cascade dynamics. Slow waves play a passive role and adopt the spectrum set by the shear Alfvén waves. Cascades composed entirely of shear Alfvén...

The anisotropy of turbulence in the fast solar wind, between the ion and electron gyroscales, is directly observed using a multispacecraft analysis technique. Second order structure functions are calculated at different angles to the local magnetic field, for magnetic fluctuations both perpendicular and parallel to the mean field. In both components, the structure function value at large angles...

Turbulent fluctuations in magnetohydrodynamic flows are known to become anisotropic under the action of a sufficiently strong magnetic field. We investigate this phenomenon in the case of low magnetic Reynolds number using direct numerical simulations and large eddy simulations of a forced flow in a periodic box. A series of simulations is performed with different strengths of the magnetic fiel...

Local isotropy, or the statistical isotropy of small scales, is one of the basic assumptions underlying Kolmogorov’s theory of universality of small-scale turbulent motion. The literature is replete with studies purporting to examine its validity and limitations. While, until the midseventies or so, local isotropy was accepted as a plausible approximation at high enough Reynolds numbers, variou...

Visual representations of quantitative information have proven very useful in the context of fluids engineering. In experiments Schlieren imagery for compressible flows and dye/smoke streaks for low-speed flows (Van Dyke 1982) are vivid examples of how physical behaviors and important system dynamics can be observed, giving the analyst a better understanding of the flow structures. Computationa...

McCaffrey, Katherine (PhD, Atmospheric and Oceanic Sciences) Characterizing Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data Thesis directed by: Baylor Fox-Kemper, Assistant Professor, Department of Geological Sciences, Brown University, and the Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder Turbulence is inherently chaotic and u...

Abstract We explore the multifaceted important features of turbulence (e.g., anisotropy, dispersion, and diffusion) in three-dimensional (3D) wavenumber domain ( k ∥ , ⊥,1 ⊥,2 ), by employing k-filtering technique to high-quality measurements fields particles from Magnetospheric Multiscale Mission (MMS) multi-spacecraft constellation. compute 3D power spectral densities (PSDs) magnetic electric...

The shear viscosity of the quark-gluon plasma is predicted to be lower than the collisional viscosity for weak coupling. The estimated ratio of the shear viscosity to entropy density is rather close to the ratio calculated by N = 4 super Yang–Mills theory for strong coupling, which indicates that the quark-gluon plasma might be strongly coupled. However, in the presence of momentum anisotropy, ...

Several two-equation turbulence models using isotropic eddy viscosity and wall functions are assessed by solution of the neutral atmospheric boundary layer over a flat surface and wind flow over twoand three-dimensional models and real terrain. Calculations are presented for wind flow over the Sirhowy Valley in Wales, an embankment along the Rhine in Germany and the Askervein Hill in Scotland. ...