Aerospace Engineering Commons^™

Implementation Of Gy-Eq For Deterministic Effects Limitation In Shield Design, John W. Wilson, Myung-Hee Y. Kim, Giovanni De Angelis, Francis A. Cucinotta, Nobuaki Yoshizawa, Francis F. Badavi

Mathematics & Statistics Faculty Publications

The NCRP has recently defined RBE values and a new quantity (Gy-Eq) for use in estimation of deterministic effects in space shielding and operations. The NCRP's RBE for neutrons is left ambiguous and not fully defined. In the present report we will suggest a complete definition of neutron RBE consistent with the NCRP recommendations and evaluate attenuation properties of deterministic effects (Gy-Eq) in comparison with other dosimetric quantities.

Lunar Lava Tube Radiation Safety Analysis, Giovanni De Angelis, J. W. Wilson, M. S. Clowdsley, J. E. Nealy, D. H. Humes, J. M. Clem

Mathematics & Statistics Faculty Publications

For many years it has been suggested that lava tubes on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava tubes has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith …

Analysis Of Error Recovery Effects On Digital Flight Control Systems, Arturo Tejada Ruiz

Electrical & Computer Engineering Theses & Dissertations

Life-critical, real-time applications like flight-by-wire aircraft, rely on closed-loop digital control systems and fault-tolerant computer systems to reliably achieve the desired operation. The computer systems, however, may be affected by random hardware/software faults induced mainly by environmental conditions such as high intensity radiated fields (HIRF) and lightning. These harsh electromagnetic environments are known to induce common­ mode faults (CMF) in aircraft electronic systems, which disrupt fault-tolerant provisions and possibly affect the operation of the digital control system. Current flight-by-wire aircraft have computer systems that can neither detect CMF nor recover from them. New systems are under investigation that can recover …

External Aerodynamics Of Heavy Ground Vehicles: Computations And Wind Tunnel Testing, Ilhan Bayraktar

Mechanical & Aerospace Engineering Theses & Dissertations

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices. Considering the latter, a thorough understanding of the airflow is a prerequisite.

The present study aims to simulate …

Modeling Aspects Of Magnetic Actuators And Magnetic Suspension Systems, V. Dale Bloodgood Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation is a study of new modeling techniques developed for magnetic suspension systems. The techniques discussed are modifications of magnetic circuit theory and fundamental eddy current models. The techniques are compared against experimental test results and finite element data. The information gained from the experimental testing is used to provide insight into magnetic bearing design.

A small-gap modeling technique called extended circuit theory is developed that incorporates information about the system gained from finite element data, or experimental data, to be included in the analytic model. The variations between the classical magnetic circuit model and the finite element model …

Active And Adaptive Flow Control Of Twin-Tail Buffet And Applications, Zhi Yang

Mechanical & Aerospace Engineering Theses & Dissertations

Modern fighter aircraft with dual vertical tails are operated at high angles of attack. The vortex generated by leading edge extension (LEX) breaks down before reaching the two vertical tails. The wake of highly unsteady, turbulent flow causes unbalanced broadband aerodynamic loading on the tails and may produce severe buffet on the tails and lead to tail fatigue failure.

Flow suction along the vortex cores (FSVC) is investigated as an active control method for tail-buffet alleviation. Suction tubes have been tilted at different angles to study the control effectiveness of suction tubes orientation. Flow field response, aerodynamic loading and aeroelastic …

Supersonic Combustion And Mixing Characteristics Of Hydrocarbon Fuels In Screamjet Engines, Ahmed A. Taha

Mechanical & Aerospace Engineering Theses & Dissertations

The combustion characteristics of gaseous propane in supersonic airflow using the rearward-facing step that is swept inward from both end sides is studied. The effect of sweeping the step on the flow field features of propane combustion is investigated.

The study of the supersonic combustion of ethylene is carried out using different combustor configurations, different main fuel equivalence ratios, and different pilot fuel equivalence ratios.

The swept step shows the ability to hold the propane flame in the supersonic air stream without extinction. It was found that the side sweeping of the combustor exhibits the high temperature and combustion products …

Advances In Space Radiation Shielding Codes, John W. Wilson, Ram K. Tripathi, Garry D. Qualls, Francis A. Cucinotta, Richard E. Prael, John W. Norbury, John H. Heinbockel, John Tweed, Giovanni De Angelis

Mathematics & Statistics Faculty Publications

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from …

Finite Element Modal Formulation For Panel Flutter At Hypersonic Speeds And Elevated Temperatures, Guangfeng Cheng

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element time domain modal formulation for analyzing flutter behavior of aircraft surface panels in hypersonic airflow has been developed and presented for the first time. Von Karman large deflection plate theory is used for description of the structural nonlinearity and third order piston theory is employed to account for the aerodynamic nonlinearity. The thermal loadings of uniformly distributed temperature and temperature gradients across the panel thickness are incorporated into the finite element formulation. By applying the modal reduction technique, the number of governing equations of motion is reduced dramatically so that the computational time of direct numerical integration …

Computational Fluid Dynamic Study Of A Nascar Winston Cup Series Race Car, Terry L. Meek Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Since the goal of NASCAR racing is to win and since drag is a force the vehicle must overcome, a thorough understanding of the drag generating airflow around and through the automobile is greatly desired. The external airflow contributes to most of the drag that a car experiences and most of the downforce the vehicle produces. Therefore, an estimate of the vehicle's performance may be evaluated using a computational aerodynamics model. This thesis presents a computational fluid dynamic (CFD) analysis of a NASCAR Winston Cup series race car to investigate the salient flow characteristics.

Before a computational analysis could be …

Investigation Of Dual-Mode Combustion With Large Upstream Interaction, Melanic Olynciw-Mills

Mechanical & Aerospace Engineering Theses & Dissertations

Dual-mode scramjet combustor configuration with significant upstream interaction is investigated numerically. The possibility of scaling the domain to accelerate the convergence an3 reduce the computational time is explored. The supersonic combustor configuration was selected to provide an understanding of key features of upstream interaction and to identify physical and numerical issues relating to modeling of dual-mode configurations. The numerical analysis was performed with vitiated air at freestream Mach number of 2.5 using hydrogen as the sonic injectant. Results are presented for two-dimensional models and a three-dimensional jet-to-jet symmetric geometry. Comparisons are made with experimental results. Two-dimensional and three-dimensional results show …

Transonic And Supersonic High Alpha Flow Prediction And Control For An Sc-X Space Vehicle, Ruobo You

Mechanical & Aerospace Engineering Theses & Dissertations

Universal Space Line (USL) is interested in developing an aerospace vehicle that flies at very high angles of attack (AOAs) through wide range of Mach numbers. The basic model configuration is called SC-X model, which consists of a blunt cone and a cylindrical afterbody. A structured O-type grid was generated for this model by numerically solving elliptic partial differential equations. The three-dimensional, unsteady, compressible, Reynolds-averaged Navier-Stokes equations coupled with Spalart-Allmaras turbulence model were used as computational tool to investigate the transonic and supersonic flows around the SC-X model pitched at AOA of 45°. For the code validation, this computational solver …

Optimal Aeroelastic Vehicle Sensor Placement For Root Migration Flight Control Applications, Abdul Ghafoor Al-Shenhabi

Mechanical & Aerospace Engineering Theses & Dissertations

An important step in control design for elastic systems is the determination of the number and location of control system components, namely sensors. The number and placement of sensors can be critical to the robust functioning of active control systems, especially when the system of interest is a large high-speed aeroelastic vehicle. The position of the sensors affects not only system stability, but also the performance of the closed-loop system. In this dissertation, a new approach for sensor placement in the integrated rigid and vibrational control of flexible aircraft structures is developed. Traditional rigid-body augmentation objectives are addressed indirectly through …

On Multifunctional Collaborative Methods In Engineering Science, Jonathan B. Ransom Sr.

Mechanical & Aerospace Engineering Theses & Dissertations

Engineers are challenged to produce better designs in less time and for less cost. Hence, to investigate novel and revolutionary design concepts, accurate, high-fidelity data must be assimilated rapidly into the design, analysis and simulation process. This data assimilation should consider diverse mathematical modeling and multi-discipline interactions necessitated by concepts exploiting advanced materials and structures. Integrated high-fidelity methods with diverse engineering applications provide the enabling technologies to assimilate these high-fidelity, multi-disciplinary data rapidly at an early stage in the design. These integrated methods must be multifunctional, collaborative and applicable to the general field of engineering science and mechanics.

Multifunctional methodologies …

Development And Testing Of A Cfd-Based Optimization System For Axially Symmetric Rocket Nozzles, John-Paul Shebalin

Mechanical & Aerospace Engineering Theses & Dissertations

A software system has been developed to optimize rocket nozzle shapes for maximizing their performance. It has been established in the literature that one can use computer-based optimization with the parabolized Navier-Stokes equations to optimize the dimensions of low Reynolds number rocket nozzles-micronozzles. The Nozzle Optimization System described herein uses the full Navier-Stokes equations to optimize any axially symmetric rocket nozzle for which a converged solution can be obtained.

Four nozzles are optimized using this system-conical and contoured micronozzles and conical and contoured Space Transportation System(STS)-class nozzles. The optimum cone angle (O_cone) for the conical micronozzle was …

Market Assessment Of Forward-Looking Turbulence Sensing Systems, Paul Kauffmann, Andres Sousa-Poza

Engineering Management & Systems Engineering Faculty Publications

[Executive Summary] This study examined the feasibility of the next generation of forward sensing turbulence systems for the Part 121 market segment: Enhanced X band radar, LIDAR, and a product that combines these first two technologies. Highlights of the findings include:

• On an annual basis, Part 121 carriers experience at least 567.8 turbulence related injury events that result in 687 minor flight attendant injuries, 38.4 serious flight attendant injuries, 119.5 minor passenger injuries, and 17.1 serious passenger injuries.
• The expected cost of turbulence injuries to airlines is $164,286 for a serious flight attendant injury, $25,000 for a minor flight attendant …

Finite Element Analysis And Active Control For Nonlinear Flutter Of Composite Panels Under Yawed Supersonic Flow, Khaled Abdel-Motagaly

Mechanical & Aerospace Engineering Theses & Dissertations

A coupled structural-electrical modal finite element formulation for composite panels with integrated piezoelectric sensors and actuators is presented for nonlinear panel flutter suppression under yawed supersonic flow. The first-order shear deformation theory for laminated composite plates, the von Karman nonlinear strain-displacement relations for large deflection response, the linear piezoelectricity constitutive relations, and the first-order piston theory of aerodynamics are employed. Nonlinear equations of motion are derived using the three-node triangular MIN3 plate element. Additional electrical degrees of freedom are introduced to model piezoelectric sensors and actuators. The system equations of motion are transformed and reduced to a set of nonlinear …

Nonlinear Response And Fatigue Estimation Of Surface Panels To White And Non-White Gaussian Random Excitations, Jean-Michel Dhainaut

Mechanical & Aerospace Engineering Theses & Dissertations

In stochastic structural dynamics, the majority of analyses have dealt with linear structures under stationary, Gaussian, and band-limited white noise excitations. Although these simplifying assumptions may be justified, in many processes experimental data have shown quite frequently the non-stationary and non-Gaussian characteristics of the loads. An efficient finite element modal formulation has recently been developed to extend the analysis to nonlinear structural responses. Laminated plate theory and von Karman large displacement relations are used to derive the nonlinear equations of motion for an arbitrarily laminated composite panel subjected to combined acoustic and thermal loads. The nonlinear equations of motion in …

An Integrated Risk Analysis Methodology In A Multidisciplinary Design Environment, Katrina R. Hampton

Engineering Management & Systems Engineering Theses & Dissertations

Design of complex, one-of-a-kind systems, such as space transportation systems, is characterized by high uncertainty and, consequently, high risk. It is necessary to account for these uncertainties in the design process to produce systems that are more reliable. Systems designed by including uncertainties and managing them, as well, are more robust and less prone to poor operations as a result of parameter variability.

The quantification, analysis and mitigation of uncertainties are challenging tasks as many systems lack historical data. In such an environment, risk or uncertainty quantification becomes subjective because input data is based on professional judgment. Additionally, there are …

The Fundamental Use And Extension Of Mode Stirred Chambers, Stephen A. Scearce

Electrical & Computer Engineering Theses & Dissertations

Mode stirred chambers are used to perform radiated susceptibility tests on equipment that is expected to operate normally when exposed to electromagnetic (EM) fields. These tests are useful in identifying failure events in airborne equipment and other electronic equipment that are exposed to EM fields. This thesis is focused on further defining the operating environment of mode stirred chambers and relating the electromagnetic environment in the chamber to the electromagnetic environment of an actual aircraft. The majority of mode stirred chamber tests are implemented by using mechanical mode stirring. Mechanical mode stirring is the process of varying boundary conditions in …

Curvilinear Interface Methodology For Finite-Element Applications, Ollie James Rose

Mechanical & Aerospace Engineering Theses & Dissertations

Recent trends in design and manufacturing suggest a tendency toward multiple centers of specialty which results in a need for improved integration methodology for dissimilar finite element or CFD meshes. Since a typical finite element or CFD analysis requires about 50% of an engineers effort to be devoted to modeling and input, there is a need to advance the state-of-the-art in modeling, methodology. These two trends indicate a need to for the capability to combine independently-modeled configurations in an automated and robust way without the need for global remodeling. One approach to addressing this need is the development of interfacing …

Piezoceramic Actuator Placement For Acoustic Control Of Panels, Jeffrey S. Bevan

Mechanical & Aerospace Engineering Theses & Dissertations

Optimum placement of multiple traditional piezoceramic actuators is determined for active structural acoustic control of flat panels. The structural acoustic response is determined using acoustic radiation filters and structural surface vibration characteristics. Linear Quadratic Regulator (LQR) control is utilized to determine the optimum state feedback gain for active structural acoustic control. The optimum actuator location is determined by minimizing the structural acoustic radiated noise using a modified genetic algorithm. Experimental tests are conducted and compared to analytical results.

Anisotropic piezoceramic actuators exhibit enhanced performance when compared to traditional isotropic piezoceramic actuators. As a result of the inherent isotropy, these advanced …

Approximation Model Building For Reliability & Maintainability Characteristics Of Reusable Launch Vehicles, Resit Unal, W. Douglas Morris, Nancy H. White, Roger A. Lepsch, Richard W. Brown

Engineering Management & Systems Engineering Faculty Publications

This paper describes the development of parametric models for estimating operational reliability and maintainability characteristics for reusable launch vehicle concepts, based on vehicle size and technology support level. A reliability and maintainability analysis tool (RMAT) and response surface methods are utilized to build parametric approximation models for rapidly estimating operational reliability and maintainability characteristics such as mission completion reliability. These models that approximate RMAT, can then be utilized for fast analysis of operational requirements, for lifecycle cost estimating and for multidisciplinary design optimization.

An Improved Thermal Mass Flow Controller For Hazardous And Precision Applications, William J. Alvesteffer

Mechanical & Aerospace Engineering Theses & Dissertations

A new mass flow controller has been designed which responds very rapidly to changes in control settings. The design was evolved after carefully studying the internal flow and the sources for thermal lag and other non-linear behavior. After discussing an overview of the basic mass flow controller operating principles, data will be presented which characterize the basic building blocks of an advanced flow sensor design. Subsequently, a flow model and control strategy have been developed and tested which reduce response lag significantly. Results of the new design, obtained experimentally under various transient conditions, will be discussed.

Long-Term Aircraft Structural Integrity Prediction Under The Influence Of Feedback Control, Si-Bok Yu

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis investigates the influence of feedback control, and other factors associated with loading characteristics, on fatigue damage reduction and long-term integrity of aircraft structural components. An actively controlled flexible aircraft model and a new state space modeling procedure for crack growth are utilized to uncover important factors which influence airframe crack growth. A matrix of simulation test cases is constructed to cover such variables as open-loop operation, nominal closed-loop operation, perturbed closed-loop operation (i.e., feedback gain variation), nominal maneuver profile, perturbed maneuver profile (including overload strength and frequency), atmospheric gust, and mean stress level. Simulation output data including crack …

Suppression Of Post-Buckling Deflection And Panel-Flutter Using Shape Memory Alloy, Mohammad Tawfik Abo El So-Oud

Mechanical & Aerospace Engineering Theses & Dissertations

A novel concept proposed is the use of Shape Memory Alloy (SMA) to reduce the panel thermal deflection and flutter responses. SMA has unique ability to recover large prestrains completely when the alloy is heated (by aerodynamic heating in the present case) above the austenite start temperature A_s. During the recovery process, a large tensile recovery stress occurs if the SMA is restrained.

In this thesis, a panel subject to the combined aerodynamic and thermal loading is investigated. A nonlinear finite element model based on von Karman strain displacement relation is utilized to study the effectiveness of SMA …

Large Amplitude Pitching Of Supermaneuver Delta Wings Including Flow Control, Yahia A. Abdelhamid

Mechanical & Aerospace Engineering Theses & Dissertations

The unsteady, three-dimensional Navier-Stokes equations are solved to simulate and study the aerodynamic response of a delta wing undergoing large amplitude pitching motion up to 90° angle of attack. The primary model under consideration consists of a 76° swept, sharp-edged delta wing of zero thickness, initially at zero angle of attack. The freestream Mach number and Reynolds number are 0.3 and 0.45 × 106, respectively. The governing equations are solved time-accurately using the implicit, upwind, Roe flux-difference splitting, finite-volume scheme. Both laminar and turbulent flow solutions are investigated. In the laminar flow solutions, validation of the computational results is carried …

Ls-Dyna3d Modeling And Simulation For Uncontained Engine Debris Impact On Fuselage Skins, Robin Eileen Lawson

Mechanical & Aerospace Engineering Theses & Dissertations

Impact and penetration events for uncontained engine debris on fuselage skins are simulated using the LS-DYNA3D finite element analysis code. The LS-DYNA3D code is a nonlinear transient dynamic simulation tool with contact algorithms for impact. A finite element analysis is used to simulate the penetration of aluminum plates impacted by titanium impactors on aircraft-like skin panels. By gaining a more comprehensive understanding of this dynamic impact event, this work is meant to contribute to improving designs for damage tolerance and residual strength by providing modeling and analysis guidelines for the analyst.

Parametric studies are performed to determine the influence of …

Jet Stability And Noise Computations Using Direct Numerical Simulation, Farouk Owis

Mechanical & Aerospace Engineering Theses & Dissertations

The computations of axisymmetric jet noise with symmetric disturbances are investigated using the direct numerical simulation of the unsteady compressible Navier-Stokes equations. High order accurate numerical schemes are employed for the solution of the governing equations. The investigation shows that MacCormack schemes with operator splitting and minimum dispersion error can be used to predict noise radiated from subsonic and supersonic jets with low and high Reynolds numbers. In addition, different kinds of nonreflecting boundary conditions are used at the inflow and outflow boundaries. These boundary conditions include characteristic boundary conditions, buffer domain technique and perfectly matching layer method. The results …

Development And Application Of Adaptive Dynamic Grids For Wake Vortex/Ground Interaction, Ilker Emin Türkgeldi

Mechanical & Aerospace Engineering Theses & Dissertations

An adaptive and dynamic grid approach is developed for the numerical computations of wake vortex flow problems with ground interaction. The unnecessary grid points at the far field of the original, large, single zone grid are removed for computational efficiency. Next, the grid is modified into an adaptive one, where the fine core region keeps track of the vortices and can be split into two regions when the vortex separation distance exceeds a specified limit length. In the final step a multi zonal feature is added to this grid by means of two embedded grids placed at the vortex centers …