The spherical torus edge region is among the most challenging regimes for plasma turbulence simulations. Here, we measure the spatial and temporal properties of ion-scale turbulence in the steep gradient region of H-mode pedestals during edge localized mode-free, MHD quiescent periods in the National Spherical Torus Experiment. Poloidal correlation lengths are about 10 qi, and decorrelation tim...

in this paper, effects of the cross shore and groyne wall slopes on flow parameters around an impermeable groyne were considered using a three-dimensional numerical cfd model (i.e., fluent). the k-ε turbulence model was used to evaluate the reynolds stresses. the model was first applied to a vertical groyne on a flat bed and the model results were compared with the relevant experimental data. t...

We study weak Alfvenic turbulence of an incompressible, magnetized fluid in some detail, with a view to developing a firm theoretical basis for the dynamics of small-scale turbulence in the interstellar medium. We prove that resonant 3-wave interactions are absent. We also show that the Iroshnikov-Kraichnan theory of incompressible, magnetohydrodynamic turbulence-which is widely accepted--descr...

The prediction of the entropy generation rate in laminar shear layers is treated as steady, even in the presence of high levels of free stream turbulence. Here we highlight the deficiencies of this approach by quantifying the magnitude of entropy generation rate fluctuations in the laminar boundary layer subjected to free stream turbulence. We find fluctuation levels in excess of 100% in the ne...

This paper surveys the basic ideas and results on fundamental models of drift wave turbulence, the formation of zonal flows, shear suppression of turbulence and transport, coupled drift wave and zonal flow dynamics, and application to transport bifurcations and transitions. Application to vortex dynamics and zonal flow phenomena in EMHD systems are discussed, as well. These are relevant to aspe...

Relaxation oscillations of transport barriers are studied by three dimensional turbulence simulations. Barriers generated by an imposed ExB shear flow are found to relax intermittently on confinement time scales, even when fluctuations of the ExB shear flow are suppressed. A relaxation event has a complex dynamical behavior, characterized by the intermittent growth of a mode at the barrier cent...

Particle Image Velocimetry (PIV) measurements for six separate flow bypass ratio five nozzle configurations have recently been obtained in the NASA Langley Jet Noise Laboratory. The six configurations include a baseline configuration with round core and fan nozzles, an eight-chevron core nozzle at two different clocking positions, and repeats of these configurations with a pylon included. One r...

Two-dimensional measurements of density fluctuations in the DIII-D tokamak, obtained with the Beam Emission Spectroscopy diagnostic, have allowed for construction of images and movies of plasma turbulence which are greatly aiding an understanding of tokamak turbulence phenomena. The measurements are obtained in the radial and poloidal plane at a spatial resolution of near 1 cm (about five ion g...

One of the scientific success stories of fusion research over the past decade is the development of the E3B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L ~low! to H ~high! transition. This concept has the universality ...