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 Publication
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Articles 1  10 of 10
FullText Articles in Physics
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Mechanical & Aerospace Engineering Theses & Dissertations
At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible NavierStokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe fluxdifference splitting, finite volume scheme is used for the numerical computations. Both locallyconical and threedimensional solutions of the NavierStokes equations are obtained.
The asymmetric flow over fivedegree semiapex angle ...
Dosimetry Of HighEnergy HeavyIon Beams Using EnergyDependent Green's Functions, Sang Yull Chun
Dosimetry Of HighEnergy HeavyIon Beams Using EnergyDependent Green's Functions, Sang Yull Chun
Physics Theses & Dissertations
A theoretical description of the transport of highcharge and highenergy (HZE) ion bombardment of biological tissue is developed. The energydependent Green’s functions and particle fluxes are obtained for two boundary distributions  the monoenergetic and the Gaussian. Approximate energydependent Green’s functions for the collision terms are obtained for computational simplicity. As an application of the energydependent Green’s function method, dosimetric quantities, such as dose, doseequivalent, and average quality factor, for 600A MeV^{56}Fe , 517A MeV ^{40}Ar, and 625A MeV ^{20}Ne ion beams incident on a water target are obtained and compared with the values obtained ...
Strong Magnetic Field Effects And Molecular Processes With Applications To White Dwarfs, Phillip C. Stancil
Strong Magnetic Field Effects And Molecular Processes With Applications To White Dwarfs, Phillip C. Stancil
Physics Theses & Dissertations
Radiative transitions of hydrogenlike atoms in external magnetic fields of strength applicable to magnetic white dwarfs, i.e. B < 10^{3} megagauss, have been investigated for fieldfree principal quantum numbers n < 6. Finite proton mass corrections are included. Relativistic corrections are also investigated. Transition probabilities are determined using the length, velocity, and acceleration forms of the electric dipole operator. Discrepancies between previous calculations and magnetic white dwarf observations of lowlying boundbound transitions have been studied. New results for highlying transitions are also obtained.
The transition probability for the hydrogenlike 2s twophoton decay has been investigated and shown to increase substantially with field strength. The computed twophoton spectra show resonances and interference minima. Anomalous Zeeman depolarization features are found in computed twophoton polarization spectra of alkali atoms in laboratory strength magnetic fields. A previously observed fine structure depolarization feature is shown to decay with decreasing field strength.
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Mechanical & Aerospace Engineering Theses & Dissertations
The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex threedimensional configurations as well as unsteady moving boundary ...
Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, GuanWei Yen
Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, GuanWei Yen
Mechanical & Aerospace Engineering Theses & Dissertations
A computational method is developed to solve the coupled governing equations of an unsteady flowfield and those of rigidbody dynamics in six degreesoffreedom (6DOF). This method is capable of simulating the unsteady flowfields around multiple component configurations with at least one of the components in relative motion with respect to the others. Two of the important phenomena that such analyses can help us to understand are the unsteady aerodynamic interference and the boundaryinduced component of such a flowfield. By hybridizing two dynamic domain decomposition techniques, the grid generation task is simplified, the computer memory requirement is reduced, and the governing ...
High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin
High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin
Physics Theses & Dissertations
The problem of energetic nucleon transport through extended bulk matter is considered in the context of the 'straight ahead' approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes 'coupling' of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks ...
Prediction Of The Stochastic Behavior Of Nonlinear Systems By Deterministic Models As A Classical TimePassage Probabilistic Problem, L. M. Ivanov, A. D. Kirwan Jr., O. V. Melnichenko
Prediction Of The Stochastic Behavior Of Nonlinear Systems By Deterministic Models As A Classical TimePassage Probabilistic Problem, L. M. Ivanov, A. D. Kirwan Jr., O. V. Melnichenko
CCPO Publications
Assuming that the behaviour of a nonlinear stochastic system can be described by a Markovian diffusion approximation and that the evolution equations can be reduced to a system of ordinary differential equations, a method for the calculation of prediction time is developed. In this approach, the prediction time depends upon the accuracy of prediction, the intensity of turbulence, the accuracy of the initial conditions, the physics contained in the mathematical model, the measurement errors, and the number of prediction variables. A numerical application to zonal channel flow illustrates the theory. Some possible generalizations of the theory are also discussed.
Multigrid Acceleration Of TimeDependent Solutions Of NavierStokes Equations, Sarafa Oladele Ibraheem
Multigrid Acceleration Of TimeDependent Solutions Of NavierStokes Equations, Sarafa Oladele Ibraheem
Mechanical & Aerospace Engineering Theses & Dissertations
Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the timedependent Euler and NavierStokes equations. The BeamWarming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in ...
A Fast Numerical Solution Of Scattering By A Cylinder: Spectral Method For The Boundary Integral Equations, Fang Q. Hu
A Fast Numerical Solution Of Scattering By A Cylinder: Spectral Method For The Boundary Integral Equations, Fang Q. Hu
Mathematics & Statistics Faculty Publications
It is known that the exact analytic solutions of wave scattering by a circular cylinder, when they exist, are not in a closed form but in infinite series which converge slowly for high frequency waves. In this paper, a fast numerical solution is presented for the scattering problem in which the boundary integral equations, reformulated from the Helmholtz equation, are solved using a Fourier spectral method. It is shown that the special geometry considered here allows the implementation of the spectral method to be simple and very efficient. The present method differs from previous approaches in that the singularities of ...
Reflection HighEnergy ElectronDiffraction Study Of Surface Disorder And Anomalous Expansion Of Pb(100), D. Tang, H. E. ElsayedAli
Reflection HighEnergy ElectronDiffraction Study Of Surface Disorder And Anomalous Expansion Of Pb(100), D. Tang, H. E. ElsayedAli
Electrical & Computer Engineering Faculty Publications
The temperaturedependent surface structural behavior of Pb(100) is studied using reflection highenergy electron diffraction. Anomalous surface expansion for temperatures between room temperature to about 500 K is observed. A high density of surface vacancies appears at temperatures above ~ 500 K. © 1994 The American Physical Society.