Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 32 for “"Velocity shear"”.
-
Resistive instabilities in magnetically confined fusion plasmas with velocity shear and rotation
… magnetohydrodynamic stability with equilibrium velocity, the leading-order effects of velocity shear and rotation on linear tearing layer stability are studied for tokamak equilibria. The separation-of-time-scales formalism needed for a proper formulation of ideal and resistive stability …
-
Three-Dimensional Fluid Simulations of Mid-Latitude Ionospheric Processes with Hybrid Chebyshev/Fourier Pseudo-Spectral Methods
… the role of background electric fields and velocity shear in shaping turbulence. Using a fixed background density profile and varying latitudinal velocity profiles, the model explored how velocity shear location and neutral wind direction affect turbulence spectra of the GDI and their …
-
Examining Plasma Instabilities as Ionospheric Turbulence Generation Mechanisms Using Pseudo-Spectral Methods
… are used to examine the latitudinal density and velocity profiles of SAPS. It is found that the GDI is stabilized by velocity shear and therefore will only generate density irregularities in regions of low velocity shear. Furthermore, the density irregularities cannot extend through regions of …
-
Stratification on the Skagit Bay tidal flats
… of stratification by the depth-averaged velocity, straining of the horizontal density gradient by velocity shear, and turbulent mixing are shown to be the dominant processes. On the south-central flats (near the south fork river mouth) velocities are roughly rectilinear, and the largest …
-
Stratification on the Skagit Bay tidal flats
… of stratification by the depth-averaged velocity, straining of the horizontal density gradient by velocity shear, and turbulent mixing are shown to be the dominant processes. On the south-central flats (near the south fork river mouth) velocities are roughly rectilinear, and the largest …
-
Field and laboratory observations of small-scale dispersion in wetlands
… structure behind stems (hold-up dispersion), velocity deficits well downstream of stems (stem-wake dispersion), or transverse gradients in longitudinal velocity (shear dispersion). To better understand the relative magnitude of these various dispersive processes, measurements were taken of …
-
Experimental Investigation of Sheared Flow Stabilization of Z-pinches
… calculations of z-pinch stability with an axial velocity shear predict that a supersonic axial flow with a radial gradient is capable of stabilizing the MHD instabilities [3][4][5]. A sheared flow can be introduced to a pinch by using a conical wire array with a fine metallic wire on axis [6]. …
-
Numerical analysis and visualization of the ionospheric Kelvin-Helmholtz instability
… density and electric potential. The transverse velocity is also monitored, as well as the density power spectrum. The simulation is performed for different velocity shear scale lengths to observe how varying the shear length effects the development of the KHI. The simulation results agree with …
-
The gravity wave-critical level interaction
… large, prevent the formation of unstable velocity shears. A Viscous Stability Criterion is obtained and its predictions are found to be consistent with observations in a number of laboratory, atmospheric, and oceanic critical level flows. Nonlinear and time dependent effects are found to …
-
A granular flow model of an annular shear cell
… stress model of a horizontal annular shear cell is developed. This shear stress model was used in an athermal energy balance to develop a description of the power dissipation, which drives the communition purpose of the IsaMillTM. The key ingredients (velocity, shear rate and volume …
-
The vertical structure of the wind-driven circulation
… is conserved, the wave enstrophy. In chapter 5 shear dispersion in an oscillatory velocity field, similar to that of an inertial oscillation, is discussed. The goal of this section is to develop intuition about the role of internal waves in horizontal ocean mixing. The problem is examined using …
-
Teleseismic imaging of the Slave craton and implications for the assembly of cratonic lithosphere
… the depth dependence of Rayleigh wave phase velocity, shear wave velocity, and azimuthal anisotropy of the Slave cratonic lithosphere. The tomographic images reveal high shear wave velocities associated with a particularly depleted, cold, and unperturbed Archean cratonic lithosphere. …
-
H (sub) alpha & Neutral Density Scaling in the Maryland Centrifugal eXperiment
… test the concepts of centrifugal confinement and velocity shear stabilization which may allow scaleability to a fusion reactor. These two concepts, however, rely on supersonic plasma fluid velocities, which, apart from possible plasma instabilities, could be greatly reduced by fluid drag with …
-
Aspects of southern ocean transport and mixing
… for estimating diffusivity from profiles of velocity shear acquired by moored acoustic Doppler current profilers. An 18-month time series of diffusivity estimates is derived with a median of 3.3 × 10−4 m2 s−1 and a range of 0.5 × 10−4 m2 s−1 to 57 × 10−4 m2 s−1. There is no significant signal …
-
Thermocapillary Convection During Laser Surface Heating (Surface Tension)
… first solved. It is found that the recirculating velocity is much higher than the scanning speed. A perturbation solution is therefore sought for the three-dimensional case. The basic solution corresponds to the stationary axisymmetric case. The scanning case is obtained by perturbing the basic …
-
Photoelastic study of dense granular free-surface flow rheology and size segregation
… coarse-grained profiles for packing fraction, velocity, shear rate, inertial number, and stress tensor components, as well as statistical observations drawn from the measurable forces. Despite the highly fluctuating and seemingly random nature of the force network, we draw analogies between …
-
Edge radial electric field studies via charge exchange recombination spectroscopy on the Alcator C-Mod Tokamak
It is commonly accepted that ExB velocity shear is responsible for the suppression of edge turbulence, which reduces the losses of both energy and particles across magnetic field lines and results in the formation of edge transport barriers and high-confinement mode (H-mode) in tokamak plasmas. …
-
Full-Scale Shake Table Cyclic Simple Shear Testing of Liquefiable Soil
… works towards comparing large-scale simple-shear liquefaction testing to small-scale simple-shear liquefaction testing of a #2/16 Monterey sand specimen. The bucket top was modified in order to apply a vertical load to the soil skeleton to replicate overburden soil conditions. Access ports …
-
Granular flow modelling of rotating drum flows using positron emission particle tracking
… (PEPT) data we recover the key ingredients (velocity, shear rate, volume concentration, bed depth) for developing, testing and calibrating granular flow models. In this regard, 5 mm and 8 mm glass beads are rotated within a 476 mm diameter mill, fitted with angled lifter bars along the inner …
-
Solar Wind-Magnetosphere-Ionosphere Coupling: Multiscale Study with Computational Models
… hybrid (EIH) instability could relax the velocity shear within the DF via emitting lower hybrid waves. The velocity inhomogeneity driven instability is highlighted as an important mechanism for energy conversion and wave emission during the solar wind-magnetosphere coupling, which has been …
Page 1 of 2