VTechWorks Repository :: Browsing by Author "Brown, Eugene F."

Browsing by Author "Brown, Eugene F."

Now showing 1 - 20 of 39

1. Tests of the coupled shock tube/mass-spectrometer technique ; 2. The pyrolysis of neopentane by atomic resonance absorption spectrophotometry
Bernfeld, Diane Lois (Virginia Polytechnic Institute and State University, 1982)
Part 1 The coupled shock-tube/mass spectrometer apparatus is characterized in terms of its capabilities for chemical kinetic studies. Criteria for doing kinetic measurements by this experimental technique are discussed. The characterization experiments showed that our apparatus was capable of giving plausible signal shapes for non-reactive dynamic shots at P₁ = 5 torr. Measurements of ion current under static conditions showed that response of the quadrupole mass spectrometer was linear over a range of P₁ = 0-5 torr. Schlieren measurements indicated that the shock wave velocity was erratic and non-reproducible over the last 5 feet of the test section and that the velocity at the endwall could not be predicted from the schlieren data. The electron beam width was found to be ~.1" and the implications of this measurement for further studies on the free jet are outlined. The present beam width is suitable for jet studies in which bulk ionization of gas from a cross-section of the jet is performed. Design improvements needed for future reactive studies on our system are reviewed. In addition, experimental studies of jet risetime with a pulsed molecular beam apparatus showed poor agreement between the experimental and theoretical jet risetimes. The apparent discrepancy is discussed and possible explanations for it are given. Part 2 The rate constant k₁ for the reaction C₅H₁₂ → C₄H₉ + CH₃ was determined from reflected shock experiments (1100-1300°K) in which the progress of reaction was monitored by the appearance of H atoms. Atomic resonance absorption spectrophotometry at the Lyman-α line was performed on three mixtures (20 ppm, 10 ppm, 5 ppm) of neopentane in argon to give k₁ = .17 x 10¹⁸ exp (-84800±6200/RT) sec⁻¹. This result is in very good agreement with earlier single pulse shock tube experiments. In addition, calibration experiments for H atom were performed by shock-heating two mixtures (10 ppm and 5 ppm) of neopentane in argon. The results obtained were in good agreement with previous calibration data.
3-D flow and performance of a rocket pump inducer at design and off-design flow rates
Doan, Andrew W. (Virginia Tech, 1994-08-05)
The ADP rocket pump inducer was studied computationally using a 3-D Navier-Stokes solver, The Moore Elliptic Flow Program. Design and off-design flow rates were simulated to qualitatively and quantitatively study the effects of flow rate on the flow and performance. Several views of the results were created to aid flow visualization. The 3-D laser measurements made by Rocketdyne were used for comparison. The velocity magnitudes as well as the flow patterns within the inducer match well between the calculated and measured results. The axial velocity distribution and the rotary stagnation pressure, losses, are predicted very well by the calculation. The internal flow patterns developed in the simulation as expected, with radial outflow in the blade boundary layers. The tip leakage flow formed a recirculation region, a toroidal shaped vortex at the tip leading edge of the blades. The associated backflow forms a blockage that varies with flow rate. The thermodynamic performance was evaluated by calculating the contributions to pressure rise, the pump characteristic, the contributions to moment of momentum, and the efficiency. The centrifugal effect and relative velocity effect were found to vary with flow rate. The effective inlet throat radius, which governs these two effects, changes with flow rate because of the recirculation blockage. The shear on the blades was found to produce a small fraction of the work in the inducer, and most was produced by the pressure difference across the blade. The inducer efficiency was about 89%, and increased with decreasing flow rate in the range of flow rates considered, from 89% to 110% of the design flow rate.
CFD analysis and redesign of centrifugal impeller flows for rocket pumps
Lupi, Alessandro (Virginia Tech, 1993-12-05)
The analysis and redesign of a centrifugal impeller for a rocket pump is presented in this thesis. A baseline impeller was designed by Rocketdyne for the NASA Marshall Pump Consortium. Initially, the objective was to reduce the circumferential exit flow distortion of the baseline impeller. Later in the study, the objective became raising the head coefficient of the impeller. The study presented in this thesis was also undertaken to demonstrate current CFD capabilities for impeller design. A literature review includes an overview of centrifugal impeller geometries and configurations. Centrifugal impeller performance and secondary flows are discussed, and a summary of studies on the effects of impeller exit and diffuser inlet velocity distortion on diffuser performance is also presented. The flow calculation details and the results of the baseline impeller flow calculations are described. Fourteen redesigned impeller geometries were analyzed using the Moore Elliptic Flow Program, and the results were compared to the baseline geometry in terms of head rise, losses, and exit flow distortions. A final geometry was chosen; this geometry will be built and tested by Rocketdyne. The results show that backward blade lean can be effective in red using the exit flow distortion of the impeller. Tip slots or holes were not beneficial because of the large inlet boundary layer. Also, it appears possible to raise the head coefficient of the baseline impeller without creating excessive flow distortion. The planned testing is necessary to verify the predictions of the flow code.
Characteristics of the High Speed Gas-Liquid Interface
Weiland, Christopher Jude (Virginia Tech, 2009-12-02)
The objective of this dissertation was to investigate physical characteristics of high speed gas-liquid interfaces for the cases of subsonic, transonic, and supersonic gas jets submerged underwater and the transient development of an underwater projectile reaching the supercavitating state. These studies are motivated by the need to understand the basic physics associated with a novel submersible missile launcher termed the Water Piercing Missile Launcher (WPML). This dissertation presents the first study of high speed round and rectangular gas jets submerged underwater utilizing a global optical measurement technique. This technique allows quantitative measurement of the entire gas jet and the interfacial motion. Experimental results indicate that the penetration of the gas jets into a quiescent liquid is strongly influenced by the injection mass flow and the nozzle geometry. In contrast, the oscillations of the interface are influenced by the injection Mach number. The transition from a momentum driven to a buoyant jet is determined using a characteristic length scale that appears to be in good agreement with experimental observations. Moreover, the unsteadiness of the interface appears to be governed by both Kevin-Helmholtz and Rayleigh-Taylor instabilities. This dissertation also contains the first study of a projectile accelerating to reach the supercavitating state. Experimental results show that the transient development of the supercavity is governed by the formation of a vortex ring. Nuclei are shed from the forebody of the accelerating projectile and are entrained in the vortex ring core where they are subjected to low pressure and subsequently expand rapidly. A characteristic time scale for this supercavity development is presented.
The characterization of the flowfield of a dump combustor
Gabruk, Robert S. (Virginia Tech, 1990-09-05)
To provide quality benchmark data (that can be used in numerical simulation comparisons) and to examine the effects of combustion on a typical ramjet engine flowfield, a water-cooled, stainless steel dump combustor model was developed. A two-component Laser Doppler Anemometer (LOA) was used to measure the mean and turbulent velocities in the axial and tangential directions and provide a comparison between combusting and isothermal flows. However, before any LOA measurements could be taken, the combustor had to be configured to run in a suitably stable mode. Stability was identified by the pressure spectra obtained under various running conditions using piezoelectric pressure transducers wired to a spectrum analyzer. Operational parameters such as fuel composition, fuel injection location, acoustic configuration, and equivalence ratio were varied until instabilities were minimized. The optimal configuration ran with upstream fuel injection (premixed mode) at the duct center line and an orifice plate installed immediately upstream of the fuel injectors, with propane as the fuel. Once stability was achieved, LOA data was taken. The results showed some significant differences between the reacting and nonreacting flows. The most significant effect was the difference between the inherent recirculation regions for each case. Combustion decreased the length of the region by approximately 50 percent, while increasing the maximum negative velocities. This made for a more compact, but stronger, recirculation region. Since the recirculation region acts as the main flame holder and is a major source of turbulence, the changes in this region significantly altered the dump combustor flowfield.
Computational Modeling and Simulations of Hydrodynamics for Air-Water External Loop Airlift Reactors
Law, Deify (Virginia Tech, 2010-05-27)
External loop airlift reactors are widely used for biochemical applications such as syngas fermentation and wastewater treatment. To further understand the inherent gas-liquid flow physics within the reactors, computational modeling and simulations of hydrodynamics for air-water external loop airlift reactors were investigated. The gas-liquid flow dynamics in a bubble column were simulated using a FORTRAN code developed by Los Alamos National Laboratory, CFDLib, which employs an Eulerian-Eulerian ensemble averaged method. A two-dimensional Cartesian coordinate system was used to conduct an extensive grid resolution study; it was found that grid cells smaller than the bubble diameter produced unstable solutions. Next, closure models for drag force and turbulent viscosity were investigated for a simple bubble column geometry. The effects of using a bubble pressure model and two drag coefficient models, the White model and the Schiller-Naumann model, were investigated. The bubble pressure model performed best for homogeneous (low velocity) flows and the Schiller-Naumann model was best for all flow regimes. Based on the studies for bubble column flows, an external loop airlift reactor was simulated using both two- and three-dimensional coordinates and results for gas holdup and riser velocity agreed better with experimental data for the 3D simulations. It was concluded that when performing 2D and 3D simulations, care must be taken when specifying the effective bubble diameter size, especially at high flow rates. Population balance models (PBM) for bubble break-up and coalescence were implemented into CFDLib, validated with experiments, and simulated for the external loop airlift reactor at high inlet superficial gas velocities. The PBM predictions for multiple bubble sizes were comparable with the single bubble size simulations; however, the PBM simulations better predicted the formation of the gas bubble in the downcomer. The 3D PBM simulations also gave better predictions for the average bubble diameter size in the riser. It was concluded that a two-dimensional domain is adequate for gas-liquid flow simulations of a simple bubble column geometry, whereas three-dimensional simulations are required for the complex airlift reactor geometry. To conclude, a two-fluid Eulerian-Eulerian model coupled with a PBM is needed for quantitative as well as physical predictions of gas-liquid external loop airlift reactor flows at high inlet superficial gas velocities.
Computer-assisted synthesis of wrapping cam mechanisms
Iskandar, Kurnia Dias (Virginia Tech, 1996-06-28)
A wrapping cam mechanism consists of a cam wrapped by a belt or flexible band. An analytical method for synthesizing wrapping cam mechanisms has recently been developed. This thesis extends the previous work and describes the development of an interactive wrapping cam synthesis package based on analytical methods. The software presented in this thesis generates cam profiles for eight configurations of wrapping cam-pulley or wrapping cam-sprocket mechanisms. This software package has a graphical user interface to give intuitive interactions. The modularity of the software package increases the flexibility for future program extension. This thesis also discusses the extended synthesis methods for a wrapping cam-link mechanism.
A consistent direct-iterative inverse design method for the Euler equations
Brock, Jerry S. (Virginia Tech, 1993-04-05)
A new, consistent direct-iterative method is proposed for the solution of the aerodynamic inverse design problem. Direct-iterative methods couple analysis and shape modification methods to iteratively determine the geometry required to support a target surface pressure. The proposed method includes a consistent shape modification method wherein the identical governing equations are used in both portions of the design procedure. The new shape modification method is simple, having been developed from a truncated, quasi-analytical Taylor's series expansion of the global governing equations. This method includes a unique solution algorithm and a design tangency boundary condition which directly relates the target pressure to shape modification. The new design method was evaluated with an upwind, cell-centered finite-volume formulation of the two-dimensional Euler equations. Controlled inverse design tests were conducted with a symmetric channel where the initial and target geometries were known. The geometric design variable was a channel-wall ramp angle, 0, which is nominally five degrees. Target geometries were defined with ramp angle perturbations of J10 = 2 %, 10%, and 20 %. The new design method was demonstrated to accurately predict the target geometries for subsonic, transonic, and supersonic test cases; M=0.30, 0.85, and 2.00. The supersonic test case efficiently solved the design tests and required very few iterations. A stable and convergent solution process was also demonstrated for the lower speed test cases using an under-relaxed geometry update procedure. The development and demonstration of the consistent direct-iterative method herein represent the important first steps required for a new research area for the advancement of aerodynamic inverse design methods.
Development of a new shock capturing formula for pressure correction methods
Gupta, Ajay K. (Virginia Tech, 1993-12-05)
Several methods have been developed to capture shock waves in turbo machinery flows, such as Moore's pressure correction procedure and Denton's time marching procedure. The time marching procedure is traditionally used for transonic flow calculations, whereas the pressure correction method is better suited for incompressible and subsonic flows. However, the focus of this research is on the Moore pressure correction flow code, the Moore Elliptical Flow Program (MEFP) , to calculate shock waves in transonic compressor fans. A new pressure interpolation method, the 2M formula, is developed to improve the shock capturing capabilities of the MEFP flow code. The 2M formula is a two Mach number dependent formula, with Mach numbers Mi and M i + 1. The previously used pressure interpolation method, the M&M formula, is a one Mach number dependent formula, using the maximum of Mi and Mi + 1 . In the development of the 2M formula, J.G. Moore's stability criterion is applied to the pressure correction equation such that the center point coefficient is greater than the sum of the other positive coefficients.
The development of an instrument to control the oxygen concentration and flow rate of an air-oxygen mixture
Fletcher, J. Robert (Virginia Tech, 1977-10-05)
The equipment as designed and constructed is a workable solution to the problem of mixing air and oxygen at selectable oxygen concentrations and flow rates. Control of the flow of the individual gases is adequate with the metering elements as designed. The laminated brass stock and shim stock is easily fabricated and works well. The mechanical linkage is the weakest link in the design. The hysteresis in setting concentration and the inaccuracies in setting concentration are primarily related to poor design in the linkage. Ways to possibly improve the linkage are discussed in the Recommendation section of this thesis. The only problem with the read-out design is at low flow rates, i. e., less than 5000 cm³/min (5 -(min)) the scale sticks at times.
The Dynamics of Stall and Surge Behavior in Axial-Centrifugal Compressors
Cousins, William T. (Virginia Tech, 1997-12-02)
The phenomena of stall and surge in axial-centrifugal compressors is investigated through high-response measurements of both the pressure field and the flowfield throughout the surge cycle. A unique high-response forward-facing and aft-facing probe provides flow information. Several axial-centrifugal compressors are examined, both in compressor rigs and engines. Extensive discussion is presented on the differences in axial and centrifugal rotors and their effect on the system response characteristics. The loading parameters of both are examined and data is presented that shows the increased tolerance of the centrifugal stage to instability. The dynamics of the compressor blade response are shown to be related to the transport time of a fluid particle moving through a blade passage. The data presented provides new insight into the dynamic interactions that occur prior to and during stall and surge. In addition, the inception of rotating stall and the inception of surge are shown to be the same phenomena . An analytical dynamic model (DYNTECC) is applied to one of the compression systems and the results are compared to data. The results show that the model can capture the global effects of rotating stall and surge. The data presented, along with the analytical results, provide useful information for the design of active and passive stall control systems.
The effect of blade solidity on the aerodynamic loss of a transonic turbine cascade
Doughty, Roger L. (Virginia Tech, 1991-04-05)
Past research at Virginia Tech (VPI) explored the aerodynamic loss of the transonic VPI turbine blade, which 1s based on the pitchline profile of a high pressure turbine blade for a large commercial aircraft gas turbine. The current experiment explores the loss of the VPI blade for different axial solidity ratios near the design point. Ten percent changes in the solidity ratio were accomplished by varying the blade pitch and changing the blade stagger to maintain a constant throat to spacing ratio. Reaction, exit angle and exit Mach number were kept constant with this method. Cascades with three different solidities were tested in VPI’s transonic blowdown wind tunnel. Downstream total pressure loss and static pressure measurements were obtained. In addition, inviscid calculations were made for each case. Static pressure contours and Mach number profiles from the calculations were compared with the experimental results. A ten percent decrease in solidity caused no cascade loss penalty as compared to the Baseline solidity for a wide range of Mach numbers. Calculated blade Mach number profiles agreed well with experimental profiles except on the suction side near the throat and downstream of the shock/boundary layer interaction. Predicted downstream static pressure values agreed well with experimental values, except that the inviscid code tended to over-predict the pressure rise across the suction side shocks.
Experimental determination of strain rates in stretched laminar diffusion flames
Long, Scott R. (Virginia Tech, 1992-09-05)
A laser Doppler anemometer was used to measure the axial and radial velocity components of hydrogen-air counterflow diffusion flames (CFDF). An axisymmetric opposed jet burner (OJB) used seeded air in one cylindrical tube, and a hydrogen-nitrogen mixture in the opposing cylindrical tube. Velocity measurements were made at four different operating flow rates, and were used to compute the associated strain rate fields. The results were used to qualitatively assess current CFDF modeling schemes, and to expand the knowledge of the fluid velocity field behavior within these flames. The data show behavior qualitatively consistent with most models and experimental studies: the radial velocity is essentially linear with radial position, and the velocity data collapse to functions of axial position only for regions away from the stagnation plane. However, the data also show a variable strain rate field and a relatively thick reaction zone, which are both inconsistent with CFDF models. The axial velocity fields also behaved unexpectedly as the operating flow rates were increased, transitioning from the characteristic N -shaped profile to an asymptotically-approaching profile.
An experimental investigation of a turbulent junction vortex
Harsh, Martin D. (Virginia Polytechnic Institute and State University, 1985)
An experimental study of the incompressible, three-dimensional, turbulent flow separation around the base of a bluff obstacle on a flat surface is described. The bluff obstacle is a streamlined, right circular cylinder mounted with its axis normal to the flat surface. The flow environment is characterized by a body Reynolds number of 183,000, based on the diameter of the circular cylinder. The study includes surface flow visualizations, surface pressure measurements, and mean flow measurements. The mean flow measurements consist of total pressure, static pressure, and velocity distributions in three planes around the base of the streamlined cylinder. The results show the presence of a large, dominant vortex in the junction between the cylinder and the flat surface. This vortex was found to consist of low total pressure fluid from the boundary layer flow upstream of the junction. In addition to the three-dimensional flow measurements, extensive measurements in the two-dimensional turbulent boundary layer on the flat surface are reported. These results show the existence of small, but statistically significant, spanwise variations in the nominally two-dimensional turbulent boundary layer. A systematic approach for estimating the wall shear stress from velocity profile data in a two-dimensional turbulent boundary layer based on the method of least squares is presented.
An experimental investigation of the turbulent flow in a closed compound channel
Kouroussis, Dimitrios (Virginia Tech, 1996-02-05)
A three-component laser Doppler anemometer was used to measure the fully developed, turbulent flow in a closed, symmetric, smooth-wall compound channel. Measurements were made across one quadrant of the cross-section since the flow was assumed symmetric. Measurements were made for a single channel Reynolds number. All mean velocity components were calculated and are reported. The mean velocity field results are in good agreement with results reported for similar geometries. The vector plots and the axial vorticity distribution reveal the existence of secondary flow cells in both the main channel and the flood plain. The maximum values of the secondary velocities are at the comer region, on the interface between the main channel and the flood plain. In this region the mean velocity gradients are large, indicating that this might be an area of high turbulence production. The distributions of all Reynolds stresses across the cross-section are reported. The Reynolds stress distributions show peak values near the interface corner region and small values near the center-line and on the axes of symn1etry of the channel. The turbulence kinetic energy distribution verifies the existence of high turbulence energy fluid in the comer region.
An experimental study of exit flow patterns in a multistage compressor in rotating stall
Gorrell, Steven Ernest (Virginia Tech, 1990-04-15)
High-response pressure measurements of a high-speed, 10- stage, axial-flow compressor operating in rotating stall are analyzed. Procedures used to digitize analog voltages and calibrate pressure transducers are presented. From total and static pressures measured at the exit of the test compressor, stall cell Mach number distributions are calculated and used to study the effects of discharge throttle levels and variable vane changes on the 10th-stage rotating stall cells. Results indicate that significant transition zones exist between the reverse flow and peak Mach number of the stall cell cycle. Since the axial Mach numbers of the stall cell cycle are constantly changing, the amount of leading and trailing edge transition zones and fully unstalled flow zones are not easily defined. A method is devised to approximate the different flow zone ranges and correlate them to in-stall pressure characteristic behavior of the 10th stage of the test compressor. Changes in the time-averaged pressure characteristics are found to correlate with changes in the rotating stall flow zones. A lower pressure coefficient appears to correspond to an increase in the ratio of trailing to leading edge transition zone size and the average transition zone size. Results also suggest that recovery hysteresis in the test compressor is characterized by reverse flow in the rotating stall cell.
Extracting dimensional geometric parameters from B-spline surface models
Jayaram, Uma (Virginia Tech, 1991-11-21)
In an integrated design environment, the common thread between the different design stages is usually the geometric model of the part. However, the requirements for the geometric definition of the design is usually different for each stage. The transformation of data between these different stages is essential for the success of the integrated design environment. For example, conceptual design systems usually deal with geometric dimensional parameters (e.g. length, radius, etc.) whereas preliminary design systems frequently require the geometry definition to be in the form of surface models. This dissertation presents the necessity and scope of creating and implementing methodologies to obtain dimensional geometric parameters from the surface description of an object. Since the study of geometric modeling and parametric surfaces is a new field, few classical methods are applicable. Methods and algorithms for the extraction of various geometry parameters are created. A few methods to pre-process and manipulate these surfaces before the parameter extraction methods can be applied are outlined. One of the most important applications of parameter extraction is in the field of aircraft design. There are two important aspects of geometry data conversion in the design cycle. The first is the conversion from conceptual CAD models to CFD compatible models. The second is the conversion from surface representations of CFD models to obtain component parameters (e.g. wing span, fuselage fineness ratio, moments of inertia, etc.). The methods created in this dissertation are used to extract geometric parameters of importance in aircraft design. This enables the design cycle to be complete and promotes integrated design. These methods have been implemented in the aircraft design software, ACSYNT. Examples of the conversion of data from B-spline surface models to dimensional geometric parameters using these methods are included. The emphasis of this dissertation is on non-uniform B-spline surfaces. Methods for obtaining geometric parameters from aircraft models described by characteristic points are also considered briefly.
Feasibility Study of a Natural Uranium Neutron Spallation Target using FLiBe as a Coolant
Boulanger, Andrew James (Virginia Tech, 2011-05-10)
The research conducted was a feasibility study using Lithium Fluoride-Beryllium Fluoride (LiF-BeF2) or FLiBe as a coolant with a natural uranium neutron spallation source applied to an accelerator driven sub-critical molten salt reactor. The study utilized two different software tools, MCNPX 2.6 and FLUENT 12.1. MCNPX was used to determine the neutronics and heat deposited in the spallation target structure while FLUENT was used to determine the feasibility of cooling the target structure with FLiBe. Several target structures were analyzed using a variety of plates and large cylinders of natural uranium with a proton beam incident on a Hastelloy-N window. The supporting structures were created from Hastelloy-N due to their anti-corrosive properties of molten salts such as FLiBe and their resistance to neutron damage. The final design chosen was a "Sandwich" design utilizing a section of thick plates followed by several smaller plates then finally a section of thick plates to stop any protons from irradiating the bottom of the target support structure or the containment vessel of the reactor. Utilizing a proton beam with 0.81 MW of proton beam power at 1.35 mA with proton kinetic energies of 600 MeV, the total heat generated in the spallation target was about 0.9 MW due to fissions in the natural uranium. Additionally, the neutrons produced from the final design of the spallation target were approximately 1.25x1018 neutrons per second which were mainly fast neutrons. The use of a natural uranium target proved to be very promising. However, cooling the target using FLiBe would require further optimization or investigation into alternate coolants. Specifically, the final design developed using FLiBe as a coolant was not practically feasible due to the hydraulic forces resulting from the high flow rates necessary to keep the natural uranium target structures cooled. The primary reason for the lack of a feasible solution was the FLiBe as a coolant; FLiBe is unable to pull enough heat generated in the target out of the target structure. Due to the high energy density of a natural uranium spallation target structure, a more effective method of cooling will be required to avoid high hydraulic forces, such as a liquid metal coolant like lead-bismuth eutectic.
An Interactive Chemical Equilibrium Solver for the Personal Computer
Negus, Charles H. (Virginia Tech, 1997-02-20)
The Virginia Tech Equilibrium Chemistry (VTEC) code is a keyboard interactive, user friendly, chemical equilibrium solver for use on a personal computer. The code is particularly suitable for a teaching / learning environment. For a set of reactants at a defined thermodynamic state given by a user, the program will select all species in the JANAF thermochemical database which could exist in the products. The program will then calculate equilibrium composition, flame temperature, and other thermodynamic properties for many common cases. Examples in this thesis show VTEC's ability to predict chemical equilibrium compositions and flame temperature for selected reactions, and demonstrate how VTEC can substitute for and aid in the design of lab experiments, and identify trends in parametric studies. The 1976 NASA Lewis Chemical Equilibrium Code (CEC76) from which VTEC has been adapted uses Lagrangian multipliers to minimize free energy. CEC76 was written for mainframe computer use. Later versions of CEC76, adapted for personal computer use are available for a fee and have a very minimal user interface.
Intrinsic Quantum Thermodynamics: Application to Hydrogen Storage on a Carbon Nanotube and Theoretical Consideration of Non-Work Interactions
Smith, Charles E. (Virginia Tech, 2012-02-01)
Intrinsic Quantum Thermodynamics (IQT) is a theory that combines Thermodynamics and Quantum Mechanics into a single theory and asserts that irreversibility and the increase of entropy has its origin at the fundamental, atomistic level. The merits and details of IQT are discussed and compared with the well-known theory of Quantum Statistical Mechanics (QSM) and the more recent development of Quantum Thermodynamics (QT). IQT is then used to model in 3D the time evolution of the adsorption of hydrogen on a single-walled carbon nanotube. The initial state of the hydrogen molecules is far from stable equilibrium and over time the system relaxes to a state of stable equilibrium with the hydrogen near the walls of the carbon nanotube. The details of the model are presented, which include the construction of the energy eigenlevels for the system, the treatment of the interactions between the hydrogen and the nanotube along with the interactions of the hydrogen molecules with each other, and the solution of the IQT equation of motion as well as approximation methods that are developed to deal with extremely large numbers of energy eigenlevels. In addition, a new extension to the theory of IQT is proposed for modeling systems that undergo heat interactions with a heat reservoir. The formulation of a new heat interaction operator is discussed, implemented, tested, and compared with a previous version extant in the literature. IQT theory is then further extended to encompass simple mass interactions with a mass reservoir. The formulation, implementation, and testing of the mass interaction operator is also discussed in detail. Finally, IQT is used to model the results of two experiments found in the literature. The first experiment deals with the spin relaxation of rubidium atoms and the second tests the relaxation behavior of single trapped ion that is allowed to interact with an external heat reservoir. Good agreement between experiment and the model predictions is found.

Browsing by Author "Brown, Eugene F."

Results Per Page

Sort Options