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Full-Text Articles in Physics

Feasibility Of Electric Field Assisted Clogging Reduction In Cold Gas Spraying Nozzle, Hendric Tronsson Jun 2020

Feasibility Of Electric Field Assisted Clogging Reduction In Cold Gas Spraying Nozzle, Hendric Tronsson

ENGS 88 Honors Thesis (AB Students)

The relatively novel cold spraying process expands its range of applications constantly. In order to continue this trend, this process still has various hurdles that need to be overcome such as clogging. Clogging within the cold gas spraying process causes porous coatings with less material properties and lower durability; a solution is needed in order to reduce the clogging and so expand the cold gas spraying applications. This study aimed to explore the feasibility of using an electric field to reduce clogging. To do so a simplified channel was used to simulate charged particle trajectory shifts under the influence of …


Hydrodynamic And Magnetohydrodynamic Computations Inside A Rotating Sphere, P. D. Mininni, D. C. Montgomery, L. Turner Aug 2007

Hydrodynamic And Magnetohydrodynamic Computations Inside A Rotating Sphere, P. D. Mininni, D. C. Montgomery, L. Turner

Dartmouth Scholarship

Numerical solutions of the incompressible magnetohydrodynamic (MHD) equations are reported for the interior of a rotating, perfectly-conducting, rigid spherical shell that is insulator-coated on the inside. A previously-reported spectral method is used which relies on a Galerkin expansion in Chandrasekhar–Kendall vector eigenfunctions of the curl. The new ingredient in this set of computations is the rigid rotation of the sphere. After a few purely hydrodynamic examples are sampled (spin down, Ekman pumping, inertial waves), attention is focused on selective decay and the MHD dynamo problem. In dynamo runs, prescribed mechanical forcing excites a persistent velocity field, usually turbulent at modest …


Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery Nov 2005

Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery

Dartmouth Scholarship

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached. The critical magnetic Reynolds for dynamo action is found, and in the turbulent flow it is observed to be nearly independent on the magnetic Prandtl number in the range from ∼0.3 to ∼0.1. Also the dependence of this threshold with the amount of mechanical helicity in the flow is studied. For the different regimes found, the configuration of the magnetic and velocity …


Velocity Field Distributions Due To Ideal Line Vortices, Thomas D. Levi, David C. Montgomery Apr 2001

Velocity Field Distributions Due To Ideal Line Vortices, Thomas D. Levi, David C. Montgomery

Dartmouth Scholarship

We evaluate numerically the velocity field distributions produced by a bounded, two-dimensional fluid model consisting of a collection of parallel ideal line vortices. We sample at many spatial points inside a rigid circular boundary. We focus on “nearest-neighbor” contributions that result from vortices that fall (randomly) very close to the spatial points where the velocity is being sampled. We confirm that these events lead to a non-Gaussian high-velocity “tail” on an otherwise Gaussian distribution function for the Eulerian velocity field. We also investigate the behavior of distributions that do not have equilibrium mean-field probability distributions that are uniform inside the …


Selective Decay And Coherent Vortices In Two-Dimensional Incompressible Turbulence, William H. Matthaeus, W. Troy Stribling, Daniel Martinez, Sean Oughton, David Montgomery May 1991

Selective Decay And Coherent Vortices In Two-Dimensional Incompressible Turbulence, William H. Matthaeus, W. Troy Stribling, Daniel Martinez, Sean Oughton, David Montgomery

Dartmouth Scholarship

Numerical solution of two-dimensional incompressible hydrodynamics shows that states of a near-minimal ratio of enstrophy to energy can be attained in times short compared with the flow decay time, confirming the simplest turbulent selective decay conjecture, and suggesting that coherent vortex structures do not terminate nonlinear processes. After all possible vortex mergers occur, the vorticity attains a particlelike character, suggested by the late-time similarity of the streamlines to Ewald potential contours.