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Full-Text Articles in Mechanical Engineering
Design Optimization Of A Non-Axisymmetric Endwall Contour For A High-Lift Low Pressure Turbine Blade, Jacob Allen Dickel
Design Optimization Of A Non-Axisymmetric Endwall Contour For A High-Lift Low Pressure Turbine Blade, Jacob Allen Dickel
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Various approaches have been used to shape the geometry at the junction of the endwall and the blade profile in high-lift low-pressure turbine passages in order to reduce the endwall losses. This thesis will detail the workflow to produce an optimized non-axisymmetric endwall contour design for a front-loaded high-lift research turbine profile. Validation of the workflow was performed and included a baseline planar and test contour case for a future optimization study. Endwall contours were defined using a series of Bezier curves across the passage to create a smooth surface. A parametric based approach was used to develop the test …
Coupling Computational Fluid Dynamics Analysis And Optimization Techniques For Scramjet Engine Design, Nathan T. Mcgillivray
Coupling Computational Fluid Dynamics Analysis And Optimization Techniques For Scramjet Engine Design, Nathan T. Mcgillivray
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Various aspects of hypersonic vehicles are being rapidly explored for improved functionality. One of the main areas of consideration is the fueling of a Supersonic Combusting Ramjet (scramjet) engine. Using Computational Fluid Dynamics (CFD), computer simulations can be performed to analyze the flow physics of a scramjet. In this research, an optimization code, Dakota, is integrated with the CFD to optimize a set of parameters to maximum thrust. In this study, the fuel injection and combustion is replaced with heat sources. This simplification greatly reduces the computational requirements. Additionally, the 3D geometry is reduced to an axisymmetric 2D geometry because …
Fabrication And Characterizations Of Lagp/Peo Composite Electrolytes For All Solid-State Lithium-Ion Batteries, Jeremy J. Lee
Fabrication And Characterizations Of Lagp/Peo Composite Electrolytes For All Solid-State Lithium-Ion Batteries, Jeremy J. Lee
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With the rise of electric vehicles and increasing dependence on mobile electronics, the demands for lithium-ion batteries have followed in tandem for their high energy and power densities. However, traditional lithium-ion batteries consisting of liquid electrolytes have limited operating temperatures and are susceptible to ignition and subsequent fires. Recently, battery research has diverged into solid state chemistry to address the aforementioned issues. In this research, we systematically investigate a series of ceramic/polymer lithium-ion conducting composite electrolytes, i.e. Li1.4Al0.4Ge1.6(PO4)3 /lithiated polyethylene oxide (LAGP/PEO). Lithiated PEO was prepared with two different lithium salts, LiBF4 and LITFSI. The impacts of the LAGP on …
Development And Thermal Management Of A Dynamically Efficient, Transient High Energy Pulse System Model, Nathaniel J. Butt
Development And Thermal Management Of A Dynamically Efficient, Transient High Energy Pulse System Model, Nathaniel J. Butt
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As technology advances, the abilities of civilian and military vehicles, both air and ground, will undoubtedly increase as well. One of the main areas of improvement is in the electronics area. The new electronics are ever smaller, use ever higher amounts of electrical power, and require ever smaller temperature tolerances. This leads to the problem of effectively managing the increasing thermal loads and temperature tolerances on these systems. One electronic system that causes concern is a high energy pulse system (HEPS). These devices have very high thermal loads (100s of kW). On an air vehicle, where thermal management by legacy …
Identification Of Nonlinear Constitutive Properties Of Damping Coatings, Mackenzie E. Tidball
Identification Of Nonlinear Constitutive Properties Of Damping Coatings, Mackenzie E. Tidball
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Scheduled and unscheduled maintenance actions are a significant cost for gas turbines. Advanced life prediction capabilities help to mitigate these costs. However, the protective thermal and damping coatings applied to the turbine rotors which can help significantly extend component life simultaneously increase the difficulty of modeling the behavior of the components due to the nonlinearity they introduce.This research approaches modeling and analysis of nonlinear coatings for turbine blades and blisks using a nonlinear constitutive law model for the coating. The theoretical frequency response of the nonlinear system is solved for using the harmonic balance method. The coefficients of the nonlinear …
Fabrication And Characterizations Of Lithium Aluminum Titanate Phosphate Solid Electrolytes For Li-Based Batteries, Anurag Yaddanapudi
Fabrication And Characterizations Of Lithium Aluminum Titanate Phosphate Solid Electrolytes For Li-Based Batteries, Anurag Yaddanapudi
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Demands for electric vehicles and flexible electronics have escalated research in developing high-performance lithium batteries based on solid-state chemistry. The present work is to develop highly-conductive and flexible solid electrolyte for such applications. Lithium aluminum titanate phosphate (LATP or Li1.3Al0.3Ti1.7(PO4)3), both in ceramic pellets and free-standing composite membranes, have been fabricated. The crystal structure, surface morphology, and ionic conductivity are systematically studied. LATP pellets are prepared using solid state reaction approach. The results indicate that calcine temperature has significant impacts on the phase impurity and sintering temperature and duration have more impacts on the grain size and porosity of LATP …
Layer-To-Layer Physical Characteristics And Compression Behavior Of 3d Printed Acrylonitrile Butadiene Styrene Metastructures Fabricated Using Different Process Parameters, Sivani Patibandla
Layer-To-Layer Physical Characteristics And Compression Behavior Of 3d Printed Acrylonitrile Butadiene Styrene Metastructures Fabricated Using Different Process Parameters, Sivani Patibandla
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Three-dimensional (3D) printing, a subset of additive manufacturing, is currently being explored heavily for actual part fabrication due to its ability to create complex objects with intricate internal features. There are several 3D printing technologies; however, the extrusion-based technology such as fused deposition modeling (FDM) is the widely used one owing to its low cost. The FDM method can be used to fabricate parts with different fill densities, fill patterns, and process parameters such as extruder temperature and print speed. In this research, influence of process parameters such as extruder temperature and speed on the physical characteristics such as the …
Constitutive Modeling Of Creep In Leaded And Lead-Free Solder Alloys Using Constant Strain Rate Tensile Testing, Eric Thomas Stang
Constitutive Modeling Of Creep In Leaded And Lead-Free Solder Alloys Using Constant Strain Rate Tensile Testing, Eric Thomas Stang
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Environmental and safety concerns have necessitated a phase-out of lead-based alloys, which are often used in electronics solder applications. In order to properly assess suitable replacement materials, it is necessary to understand the deformation mechanisms relevant to the application. In the case of electronics solder, creep is an important mechanism that must be considered in the design of reliable devices and systems. In this study, Power-Law and Garofalo constitutive creep models were derived for two medium temperature solder alloys. The first alloy is known by the commercial name Indalloy 236 and is a quaternary alloy of lead, antimony, tin, and …
Effect Of Process Parameters On The Surface Roughness And Mechanical Performance Of Additively Manufactured Alloy 718, Bo Ryan Whip
Effect Of Process Parameters On The Surface Roughness And Mechanical Performance Of Additively Manufactured Alloy 718, Bo Ryan Whip
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Metal additive manufacturing (AM) is a method to create complex components in a layer-by-layer process. Currently, there is a lack of understanding in the processing-structure-properties-performance relationship, particularly related to defects inherent to the AM process. This work investigates the relationship of process parameters, as-built surface roughness, and mechanical performance for nickel-based superalloy 718 built using laser powder bed fusion. The surface roughness of components built using varied processing parameters was characterized using both nondestructive and destructive measurement techniques. Finite element analysis was used to study the stress concentration on surface profiles. Statistical correlations are presented between contour processing parameters and …
Low Velocity Impact And Rf Response Of 3d Printed Heterogeneous Structures, Sandeep Keerthi
Low Velocity Impact And Rf Response Of 3d Printed Heterogeneous Structures, Sandeep Keerthi
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Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and …
A Look At The Optimum Slope Of A Fixed Solar Panel For Maximum Energy Collection For A One Year Time Frame, Salah Alhaidari
A Look At The Optimum Slope Of A Fixed Solar Panel For Maximum Energy Collection For A One Year Time Frame, Salah Alhaidari
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A rule-of-thumb for orientating fixed solar panels for optimum yearly collection of solar radiation that is not influenced by atmospheric effects is to face the panel due south in the Northern Hemisphere or due north in the Southern Hemisphere and to tilt the panel from the horizontal plane at an angle equal to the latitude of the location of the solar panel. The work presented in this thesis shows that this rule-of-thumb is an approximation for no-atmosphere, panel orientation; but not a precise value. This project presents a detailed method for determining the precise optimum tilt angle of a fixed …
Design And Testing Of Scalable 3d-Printed Cellular Structures Optimized For Energy Absorption, Sagar Dilip Sangle
Design And Testing Of Scalable 3d-Printed Cellular Structures Optimized For Energy Absorption, Sagar Dilip Sangle
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Sandwich panel structures are widely used due to their high compressive and flexural stiffness and strength-to-weight ratios, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures that are often based upon honeycomb topologies. Interest in additive manufacturing (AM), popularly known as 3D printing (3DP), has rapidly grown in past few years. The 3DP method is a layer-by-layer approach for the fabrication of 3D objects. Hence, it is very easy to fabricate complex structures with complex internal features that cannot be manufactured by any other fabrication processes. Due to the …
Dynamic Modeling And Simulation Of A Variable Cycle Turbofan Engine With Controls, Robert W. Buettner
Dynamic Modeling And Simulation Of A Variable Cycle Turbofan Engine With Controls, Robert W. Buettner
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Next generation aircraft (especially combat aircraft) will include more technology and capability than ever before. This increase in technology comes at the price of higher electrical power requirements and increased waste heat that must be removed from components to avoid overheating induced shutdowns. To help combat the resulting power and thermal management problem, a vehicle level power and thermal management design and optimization toolset was developed in MATLAB®/Simulink®. A dynamic model of a three-stream variable cycle engine was desired to add to the capabilities of the power and thermal management toolset. As an intermediate step to this goal, the dynamic …
Development Of Guidance Laws For A Reduced Order Dynamic Aircraft Model, Jack W. Brendlinger
Development Of Guidance Laws For A Reduced Order Dynamic Aircraft Model, Jack W. Brendlinger
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A set of guidance control laws has been developed for enabling three distinct modes of operation of a reduced order dynamic aircraft model. These include 1) a waypoint following control law, 2) a trajectory tracking control law, and 3) a set of kinematically constrained control laws for reaching a commanded altitude, speed or heading. The formulation of the reduced order model is presented so that the capabilities and limitations of the model are understood, and so that the interface architecture between the controllers and the plant is clearly defined. The controller formulations are then presented, together with sample results. The …
Analysis And Sensitivity Study Of Zero-Dimensional Modeling Of Human Blood Circulation Network, Roussel Rahman
Analysis And Sensitivity Study Of Zero-Dimensional Modeling Of Human Blood Circulation Network, Roussel Rahman
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The systemic circulation has a large number of vessels; therefore, 3-D simulation of pulse-wave propagation in the entire cardiovascular system is difficult and computationally expensive. Zero-Dimensional (Zero-D) and One-Dimensional (1-D) models are simplified representations of the cardiovascular network; they can be coupled as supplements to regional 3-D models for closed-loop multi-scale studies or be simulated as self-sufficient representations of the blood-flow network. Unlike Zero-D models, 1-D models can provide linear space-wise information for the vessels. However, Zero-D models can prove to be more useful in particular cases; as flexibility in adjusting parameters facilitate in tailoring the model to specific needs. …
An Investigation On The Stress Intensity Factor Of Surface Micro-Cracks, Sirisha Divya Arli
An Investigation On The Stress Intensity Factor Of Surface Micro-Cracks, Sirisha Divya Arli
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The contact fatigue failure in the form of micro or macro-scale pitting is an important failure mode for rolling mechanical elements, such as bearings and gears that are widely used in the automotive, aerospace and wind turbine fields. The micro-pitting process in some cases, gradually removes the surface material through fatigue wear, altering the geometry of the contact surfaces to alleviate the contact pressure decelerating the continued pitting rate. The propagation of the micro-cracks in other cases, goes deep into the material along a shallow angle, turns parallel to the surface at a certain depth, where the maximum shear or …
One Dimensional Computer Modeling Of A Lithium-Ion Battery, Ashwin S. Borakhadikar
One Dimensional Computer Modeling Of A Lithium-Ion Battery, Ashwin S. Borakhadikar
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Renewable energy storage is vitally important to many applications for which batteries are the finest choice. As energy storage technology may be applied to a number of areas that differ in power and energy requirements, modeling of battery performance is required. In recent years, a lot of research has been done in this area but, the earliest model was designed by Marc Doyle, T. F. Fuller, and J. Newman in 1993. This work involves the development of a one-dimensional computer model of a lithium-ion battery which consists of three domains: the negative electrode, the separator, and the positive electrode. The …
Dynamic Modeling Of Thermal Management System With Exergy Based Optimization, Marcus J. Bracey
Dynamic Modeling Of Thermal Management System With Exergy Based Optimization, Marcus J. Bracey
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System optimization and design of aircraft is required to achieve many of the long term objectives for future aircraft platforms. To address the necessity for system optimization a vehicle-level aircraft model has been developed in a multidisciplinary modeling and simulation environment. Individual subsystem models developed exclusively in MATLAB-SimulinkTM, representing the vehicle dynamics, the propulsion, electrical power, and thermal systems, and their associated controllers, are combined to investigate the energy and thermal management issues of tactical air vehicle platforms. A thermal vehicle level tip-to-tail model allows conceptual design trade studies of various subsystems and can quantify performance gains across the aircraft. …
3d Cfd Investigation Of Low Pressure Turbine Aerodynamics, Jacob Andrew Sharpe
3d Cfd Investigation Of Low Pressure Turbine Aerodynamics, Jacob Andrew Sharpe
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A 3-D Reynolds-Averaged Navier Stokes (RANS) model of a highly-loaded blade profile has been developed using a commercial CFD code with an unstructured/structured grid and several different turbulence models. The ability of each model to predict total pressure loss performance is examined in terms of the spanwise loss distribution and the integrated total pressure loss coefficient. The flowfield predicted by each model is investigated through comparisons of isosurfaces of Q criterion to previous Implicit Large Eddy Simulation (ILES) results. The 3-equation k-kl-¿ model was shown to provide the most accurate performance predictions for a baseline 3-D LPT geometry, and was …
Low-Velocity Impact Behavior Of Sandwich Panels With 3d Printed Polymer Core Structures, Andrew Joseph Turner
Low-Velocity Impact Behavior Of Sandwich Panels With 3d Printed Polymer Core Structures, Andrew Joseph Turner
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Sandwich panel structures are widely used in aerospace, marine, and automotive applications because of their high flexural stiffness, strength-to-weight ratio, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures, which are often based upon honeycomb topologies. The recent progress of additive manufacturing (AM) (popularly known as 3D printing) processes has allowed lattice configurations to be designed with improved thermal-mechanical properties. The aim of this work is to design and print lattice truss structures (LTS) keeping in mind the flexible nature of AM. Several 3D printed core structures were created …
Resilience And Toughness Behavior Of 3d-Printed Polymer Lattice Structures: Testing And Modeling, Mohammed Al Rifaie
Resilience And Toughness Behavior Of 3d-Printed Polymer Lattice Structures: Testing And Modeling, Mohammed Al Rifaie
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This research focuses on the energy absorption capability of additively manufactured or 3D printed polymer lattice structures of different configurations. The Body Centered Cubic (BCC) lattice structure is currently being investigated by researchers for energy absorption applications. For this thesis, the BCC structure is modified by adding vertical bars in different arrangements to create three additional configurations. Four designs or sets of the lattice structure are selected for comparison including BCC, BCC with vertical bars added to all nodes (BCCV), BCC with vertical bars added to alternate nodes (BCCA), and BCC with gradient arrangements of vertical bars (BCCG). Both experimental …
A Numerical And Experimental Investigation Of Steady-State And Transient Melt Pool Dimensions In Additive Manufacturing Of Invar 36, Chigozie Nwachukwu Obidigbo
A Numerical And Experimental Investigation Of Steady-State And Transient Melt Pool Dimensions In Additive Manufacturing Of Invar 36, Chigozie Nwachukwu Obidigbo
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The use of additive manufacturing (AM) in tooling enables low production components to be fabricated with lower costs, reduced waste, increased design flexibility and reduced lead time. Invar 36 is a popular metal tooling material known for its low coefficient of thermal expansion. This work uses thermal finite element (FE) modeling as a tool to determine the feasibility of using Invar 36 in AM and to investigate the transient effect from common scanning strategies. Results show that the steady-state melt pool dimensions behave similar to traditional AM materials for varying process parameters. Transient results show that the melt pool response …
Modeling Two Phase Flow Heat Exchangers For Next Generation Aircraft, Hayder Hasan Jaafar Al-Sarraf
Modeling Two Phase Flow Heat Exchangers For Next Generation Aircraft, Hayder Hasan Jaafar Al-Sarraf
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Two-phase heat exchangers offer the potential of significant energy transfer by taking advantage of the latent heat of vaporization as the working fluid changes phase. Unfortunately, the flow physics of the phase change process is very complex and there are significant gaps in the fundamental knowledge of how several key parameters are affected by the phase change process. Therefore, an initial investigation modeling a two-phase flow heat exchanger has been accomplished. Many key assumptions have been defined which are critical to modeling two-phase flows. This research lays an initial foundation on which further investigations can build upon. Two-phase heat exchangers …
Turboelectric Distributed Propulsion System For Nasa Next Generation Aircraft, Hashim H. Abada
Turboelectric Distributed Propulsion System For Nasa Next Generation Aircraft, Hashim H. Abada
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Next generation aircraft, more specifically NASA aircraft concepts, will include new technologies and make many advancements in fuel economy and noise. However, there are some challenges associated with the latest technologies that NASA is planning to use for the next generation aircraft. For example, these aircraft concepts require large amounts of electrical power to generate the required thrust throughout a notional flight profile. One of the new technologies is using advanced propulsion systems, such as the Turboelectric Distributed Propulsion (TeDP) system, which is significantly different from current aerospace high bypass turbofan based propulsion system. The TeDP propulsion system replaces the …
An Automated Controller Design Methodology For Six Degree-Of-Freedom Aircraft Models, Dominic J. Dierker
An Automated Controller Design Methodology For Six Degree-Of-Freedom Aircraft Models, Dominic J. Dierker
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This thesis presents an automated design methodology for development of six degree-of-freedom aircraft controllers. The essential functions required of the controller design are 1) to provide sufficient inner loop compensation to guarantee dynamic stability and acceptable handling qualities over the full flight envelope, and, 2) to enable automated mission following capabilities through implementation of outer loop trackers. A hierarchical control architecture consisting of nested nonlinear dynamic inversion control loops is proposed as a means of achieving these top level objectives. Gain tuning based on an automated linearization methodology is then suggested. Next, an automated optimal control allocation algorithm is tested …
Electrical Power And Storage For Nasa Next Generation Aircraft, Saif Al-Agele
Electrical Power And Storage For Nasa Next Generation Aircraft, Saif Al-Agele
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Next generation aircraft will incorporate more electrical power generation and storage for both a distributed electric propulsion system and onboard subsystems. The power generation in this type of aircraft will require orders of magnitude higher than today’s commercial aircrafts, thus producing many challenges. For this reason, a unique, high-powered electric propulsion system primarily powered by a turbo-generator system with electrical storage is being considered. A Simulink/Matlab model has bee created for the electrical power system of the next generation blended wing commercial aircraft proposed by NASA. The components of the electrical system include turbo-generators, generators, battery banks, and electrical distribution …
The Design And Experimental Investigation Of Novel Double-Blade Wind Turbine Models Inspired By Houck's Concept, Laura E. Carpenter
The Design And Experimental Investigation Of Novel Double-Blade Wind Turbine Models Inspired By Houck's Concept, Laura E. Carpenter
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Energy can be captured from wind turbines efficiently today. However there's always room for improvement up to the Betz's limit of 59.3% efficiency. A novel wind turbine blade was designed with double blade rotor inspired by Houck's concept in an attempt to improve the efficiency of the horizontal axis wind turbine. Scaled wind turbine models with a diameter of 150 mm were designed in SolidWorks adjusting the parameters of stagger, gap, and decalage. The general design comprises of two modern blades attached by a curved flow guide at the tip. Fourteen blade models were designed and tested to obtain power, …
Feasibility Of Attaining Fully Equiaxed Microstructure Through Process Variable Control For Additive Manufacturing Of Ti-6al-4v, Sarah Louise Kuntz
Feasibility Of Attaining Fully Equiaxed Microstructure Through Process Variable Control For Additive Manufacturing Of Ti-6al-4v, Sarah Louise Kuntz
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One of the greatest challenges in additive manufacturing is fabricating titanium structures with consistent and desirable microstructure. To date, fully columnar deposits have been achieved through direct control of process variables. However, the introduction of external factors appears necessary to achieve fully equiaxed grain morphology using existing commercial processes. This work introduces and employs an analytic model to relate process variables to solidification thermal conditions and expected beta grain morphology at the surface of and at the deepest point in the melt pool. The latter is required in order to ensure the deposited microstructure is maintained even after the deposition …
Vehicle Level Transient Aircraft Thermal Management Modeling And Simulation, Adam Donovan
Vehicle Level Transient Aircraft Thermal Management Modeling And Simulation, Adam Donovan
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Many advances in technology are expected to increase the capabilities of next generation aircraft, and these advances will increase the thermal load on the aircraft as well. In order to assess and account for these increased thermal loads, three studies were performed: a fuel pump trade study, a high energy pulsed system (HEPS) implementation study, and a legacy vehicle environmental control system (ECS) study. The fuel pump study addresses the effect of the implementation of a centrifugal fuel pump versus a variable displacement fuel pump. Traditionally, aircraft designers have used a centrifugal fuel pump over a piston based pump based …
Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.
Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.
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In this thesis, the Locally-Optimized Covariance (LOC) Kriging method is developed. This method represents a flexible surrogate modeling approach for approximating a non-stationary Kriging covariance structures for deterministic responses. The non-stationary covariance structure is approximated by aggregating multiple stationary localities. The aforementioned localities are determined to be statistically significant utilizing the Non-Stationary Identification Test. This methodology is applied to various demonstration problems including simple one and two-dimensional analytical cases, a deterministic fatigue and creep life model, and a five-dimensional fluid-structural interaction problem. The practical significance of LOC-Kriging is discussed in detail and is directly compared to stationary Kriging considering computational …