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Articles 1  17 of 17
FullText Articles in Mechanical Engineering
Improving Predictive Capabilities Of Classical Cascade Theory For Nonproliferation Analysis, David Allen Vermillion
Improving Predictive Capabilities Of Classical Cascade Theory For Nonproliferation Analysis, David Allen Vermillion
Doctoral Dissertations
Uranium enrichment finds a direct and indispensable function in both peaceful and nonpeaceful nuclear applications. Today, over 99% of enriched uranium is produced by gas centrifuge technology. With the international dissemination of the Zippe archetypal design in 1960 followed by the widespread illicit centrifuge trafficking efforts of the A.Q. Khan network, traditional barriers to enrichment technologies are no longer as effective as they once were. Consequently, gas centrifuge technology is now regarded as a highpriority nuclear proliferation threat, and the international nonproliferation community seeks new avenues to effectively and efficiently respond to this emergent threat.
Effective response first requires ...
Computational ThermalHydraulics Modeling Of Twisted Tape Enabled High Heat Flux Components, Emily Buckman Clark
Computational ThermalHydraulics Modeling Of Twisted Tape Enabled High Heat Flux Components, Emily Buckman Clark
Doctoral Dissertations
The goal of this work was to perform a computational investigation into the thermalhydraulic performance of watercooled, twisted tape enabled high heat flux components at fusion relevant conditions. Fusion energy is a promising option for future clean energy generation, but the community must overcome significant scientific and engineering challenges before meeting the goal of electricity generation. One such challenge is the high heat flux thermal management of components in fusion and plasma physics experiments. Plasma facing components in the magnetic confinement devices, such as ITER or W7X, will be subjected to extreme heat loads on the order of 1020 MW ...
Development, Analysis, And Optimization Of A SwirlPromoting Mean Flow Solution For Solid Rocket Motors, Andrew Steven Fist
Development, Analysis, And Optimization Of A SwirlPromoting Mean Flow Solution For Solid Rocket Motors, Andrew Steven Fist
Masters Theses
This work demonstrates and analyses a new flow candidate for describing the internal gaseous motion in simulated rocket motors. The fundamental features of this solution include the conservation of key system properties also incorporated in the classic TaylorCulick (TC) system (i.e. inviscid, axisymmetric, steady and rotational properties), while allowing for the development of a swirling velocity component. The work compares the new solution to the development and formulation of the classic TC system, ultimately identifying that both the new and classic solutions are special cases of the BraggHawthorne equation. Following this development, the text then explores the development of ...
Lattice Boltzmann Methods For Wind Energy Analysis, Stephen Lloyd Wood
Lattice Boltzmann Methods For Wind Energy Analysis, Stephen Lloyd Wood
Doctoral Dissertations
An estimate of the United States wind potential conducted in 2011 found that the energy available at an altitude of 80 meters is approximately triple the wind energy available 50 meters above ground. In 2012, 43% of all new electricity generation installed in the U.S. (13.1 GW) came from wind power. The majority of this power, 79%, comes from large utility scale turbines that are being manufactured at unprecedented sizes. Existing wind plants operate with a capacity factor of only approximately 30%. Measurements have shown that the turbulent wake of a turbine persists for many rotor diameters, inducing ...
Improved Modeling Of Atmospheric Entry For Meteors With Nose Radii Between 5cm And 10m, Jakob Dale Brisby
Improved Modeling Of Atmospheric Entry For Meteors With Nose Radii Between 5cm And 10m, Jakob Dale Brisby
Masters Theses
Atmospheric entry studies typically look closely at the peak heating rate that a body encounters during its trajectory. This is an extremely important phenomenon to study because it allows engineers to determine if a trajectory is possible with given materials and craft design specifications. It also allows designers to choose what type of method will be used for mitigating the enormous heat fluxes during entry. In general, it is accepted that during the supersonic flight regime the body will continue to be heated and an ablative heat shield often is used to deal with these heating processes. The theory outlined ...
Measurements Of Methyl Radicals And Temperatures By Using Coherent Microwave Rayleigh Scattering From Resonance Enhanced Multiphoton Ionization, Yue Wu
Doctoral Dissertations
This thesis includes two main parts: (I) The CH_{3}[methyl radical] detection in methane/air flames and (II) the rotational temperature measurement of O_{2}[molecular oxygen] in a variety of environments by using coherent microwave Rayleigh scattering from resonance enhanced multiphoton ionization (Radar REMPI).
In first the part, from Chapter I to Chapter III, the methyl radical detection and quantitative measurements have been conducted in hydrocarbon flame with onedimensional and twodimensional spatialresolved concentration distribution. Due to the proximity of the argon resonance state (4+1 REMPI by 332.5 nm) with the CH_{3} state (2+1 REMPI ...
Cfd Analysis Of Viscosity Effects On Turbine Flow Meter Performance And Calibration, Carl Tegtmeier
Cfd Analysis Of Viscosity Effects On Turbine Flow Meter Performance And Calibration, Carl Tegtmeier
Masters Theses
In this research turbine flow meters were studied, using computational fluid dynamics (CFD) modeling to the study effects of viscosity on the flow meters, across a wide range of operation, to improve our understanding and their performance. A threedimensional computational model was created for a typical flow meter geometry. The work began with a steady state model to provide an acceptable initial condition for further simulations. These results were input into a transient model that has a rotating zone around the rotor to provide insight into the interaction between static and rotational structures. In order to automatically adjust the rotor ...
Neutron Imaging Of Lithium (Li) Coolants Inside High Temperature Niobium (Nb) Heat Pipes, Brad Harrison Hight
Neutron Imaging Of Lithium (Li) Coolants Inside High Temperature Niobium (Nb) Heat Pipes, Brad Harrison Hight
Masters Theses
Lithium (Li) behavior inside a high temperature NbLi leading edge heat pipe was successfully imaged under induction heating operation via neutron imaging. Startup and cooldown operations gave visual confirmation of bulk Li movement using both gravity assisted and inverted operating orientations. The pipe was imaged during an operation cycle from ambient conditions, heated to a steady state temperature of 908.8 ^{0}C, and allowed to cool below 200^{°}C. The experiment was performed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, and at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee.
Tomographic images ...
Essentially Analytical Theory Closure For Space Filtered ThermalIncompressible NavierStokes Partial Differential Equation System On Bounded Domains, Mikhail Alexandrovich Sekachev
Essentially Analytical Theory Closure For Space Filtered ThermalIncompressible NavierStokes Partial Differential Equation System On Bounded Domains, Mikhail Alexandrovich Sekachev
Doctoral Dissertations
Numerical simulation of turbulent flows is identified as one of the grand challenges in highperformance computing. The straight forward approach of solving the NavierStokes (NS) equations is termed Direct Numerical Simulation (DNS). In DNS the majority of computational effort is spent on resolving the smallest scales of turbulence, which makes this approach impractical for most industrial applications even on presentday supercomputers. A more feasible approach termed Large Eddy Simulation (LES) has evolved over the last five decades to facilitate turbulent flow predictions for reasonable Reynolds (Re) numbers and domain sizes. LES theory uses the concept of convolution with a spatial ...
Fully Coupled Fluid And Electrodynamic Modeling Of Plasmas: A TwoFluid Isomorphism And A Strong Conservative FluxCoupled Finite Volume Framework, Richard Joel Thompson
Fully Coupled Fluid And Electrodynamic Modeling Of Plasmas: A TwoFluid Isomorphism And A Strong Conservative FluxCoupled Finite Volume Framework, Richard Joel Thompson
Doctoral Dissertations
Ideal and resistive magnetohydrodynamics (MHD) have long served as the incumbent framework for modeling plasmas of engineering interest. However, new applications, such as hypersonic flight and propulsion, plasma propulsion, plasma instability in engineering devices, charge separation effects and electromagnetic wave interaction effects may demand a higherfidelity physical model. For these cases, the twofluid plasma model or its limiting case of a single bulk fluid, which results in a singlefluid coupled system of the NavierStokes and Maxwell equations, is necessary and permits a deeper physical study than the MHD framework. At present, major challenges are imposed on solving these physical models ...
Multidimensional Compressible Framework For Modeling Biglobal Stability In Rocket Motors, Michel Henry Akiki
Multidimensional Compressible Framework For Modeling Biglobal Stability In Rocket Motors, Michel Henry Akiki
Doctoral Dissertations
Rocket motor stability analysis has historically been focused on two fundamental theories: the acoustic and the hydrodynamic. While the acoustic part examines the system at resonant states, the hydrodynamic component focuses on the fluidwall interactions and the vortex shedding mechanisms which are responsible for exciting the system. Traditionally, the two concepts are studied independently and their results are then superposed for a more complete solution. In this study, we analyze the problem from a hydrodynamic standpoint and extend it to include compressibility. This is realized by reducing the linearized NavierStokes and energy equations to their biglobal form assuming a twodimensional ...
Development And Verification Of A NavierStokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell
Development And Verification Of A NavierStokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell
Masters Theses
Vorticity Confinement (VC) is a numerical technique which enhances computation of fluid flows by acting as negative diffusion within the limit of vortical regions, preventing the inherent numerical dissipation present with conventional methods. VC shares similarities with large eddy simulation (LES), but its behavior is based on a stable negative dissipation of vortical structures controlled by the automatic balance between two parameters, μ [mu] and ε [epsilon].
In this thesis, threedimensional, parallelcomputing NavierStokes solvers with VC are developed using the OpenFOAM computational framework. OpenFOAM is an opensource collection of C++ libraries developed for computational fluid dynamics. Objectoriented programming concepts are ...
The Biglobal Instability Of The Bidirectional Vortex, Joshua Will Batterson
The Biglobal Instability Of The Bidirectional Vortex, Joshua Will Batterson
Doctoral Dissertations
State of the art research in hydrodynamic stability analysis has moved from classic onedimensional methods such as the local nonparallel approach and the parabolized stability equations to twodimensional, biglobal, methods. The paradigm shift toward two dimensional techniques with the ability to accommodate fully threedimensional base flows is a necessary step toward modeling complex, multidimensional flowfields in modern propulsive applications. Here, we employ a twodimensional spatial waveform with sinusoidal temporal dependence to reduce the threedimensional linearized NavierStokes equations to their biglobal form. Addressing hydrodynamic stability in this way circumvents the restrictive parallelflow assumption and admits boundary conditions in the streamwise direction ...
Continuously Variable Rotorcraft Propulsion System: Modelling And Simulation, Naveen Kumar Vallabhaneni
Continuously Variable Rotorcraft Propulsion System: Modelling And Simulation, Naveen Kumar Vallabhaneni
Masters Theses
This study explores the variable speed operation and shift response of a prototype of a two speed single path CVT rotorcraft driveline system. Here a Comprehensive Variable Speed Rotorcraft Propulsion system Modeling (CVSRPM) tool is developed and utilized to simulate the drive system dynamics in steady forward speed condition. This investigation attempts to build upon previous variable speed rotorcraft propulsion studies by:
1) Including fully nonlinear first principles based transient gasturbine engine model
2) Including shaft flexibility
3) Incorporating a basic flight dynamics model to account for interactions with the flight control system.
Through exploring the interactions between the various ...
CrossFlow, StaggeredTube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock
CrossFlow, StaggeredTube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock
Masters Theses
Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a convergingdiverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger.
It is of interest to evaluate ...
Effect Of Unsteady Combustion On The Stability Of Rocket Engines, Tina Morina Rice
Effect Of Unsteady Combustion On The Stability Of Rocket Engines, Tina Morina Rice
Doctoral Dissertations
Combustion instability is a problem that has plagued the development of rocketpropelled devices since their conception. It is characterized by the occurrence of highfrequency nonlinear gas oscillations inside the combustion chamber. This phenomenon degrades system performance and can result in damage to both structure and instrumentation.
The goal of this dissertation is to clarify the role of unsteady combustion in the combustor instability problem by providing the first quantified estimates of its effect upon the stability of liquid rocket engines. The combination of this research with a new system energy balance method, accounting for all dynamic interactions within a system ...
Modeling And Analysis Of Turbojet Compressor Inlet Temperature Measurement System Performance, Brian A Binkley
Modeling And Analysis Of Turbojet Compressor Inlet Temperature Measurement System Performance, Brian A Binkley
Masters Theses
Accurate measurement of turbine engine compressor inlet total temperature is paramount for controlling engine speed and pressure ratio. Various methods exist for measuring compressor inlet total temperature on turbojet engines with hydromechanical control. One method involves the use of an ejectordiffuser system (eductor) to pull air from the engine inlet in order to measure the incoming total temperature. Analysis of historical test data has revealed that the inlet temperature measurement can be biased at certain flight conditions causing engine misscheduling and offnominal engine operation. This bias is characterized primarily by adverse heat transfer effects and secondly by poor flow quality ...