Engineering Commons^™

Analysis Of A Non-Equilibrium Vortex Pair As Aircraft Trailing Vortices, Manuel Ayala

Mechanical & Aerospace Engineering Theses & Dissertations

Shortly after the roll-up evolution of the vortex sheet behind the wings of an aircraft, a coherent counter-rotating vortex pair emerges. Presence of this vortex pair in the downstream of an aircraft, creates unsafe conditions for other aircraft, especially near airport runways. Fundamental knowledge of the physics that govern the formation, duration and dissipation of aircraft wake vortices is desirable in order to improve aircraft operational safety. This study uses non-equilibrium pressure theory to develop an accurate model describing the physical behavior of the vortex pair created by an aircraft in the early to mid-field vortex regime. An isolated aircraft …

Gradient-Based Tradeoff Design For Engineering Applications, Lena Alexis Royster

Mechanical & Aerospace Engineering Theses & Dissertations

This research presents a formal method for gradient based tradeoff design including methods that extend to cases with singularities and cases with more performance characteristics then design variables. The goal is to find revised design variables that can achieve the targeted performance characteristics and remove any violations to the constraint functions. The tradeoff design problem is formulation in the framework of the Sequential Quadratic Programming and is solved using the gradient based method. The optimal solution is the search direction, s, which represents the most effective way to reduce the current objective and correct the current violation. In this research …

A Model-Based Systems Engineering Approach To E-Vtol Aircraft And Airspace Infrastructure Design For Urban Air Mobility, Heidi Selina Glaudel

Mechanical & Aerospace Engineering Theses & Dissertations

This paper serves to contribute to Model-Based Systems Engineering (MBSE) by following the NASA Systems Engineering Handbook framework for a Systems Engineering (SE) design approach to an Electric Vertical Takeoff and Landing (e-VTOL) aircraft and the incorporating airspace infrastructure. The focus of this study is, by using the MBSE model created, to capture the technical requirements definition and design intent of the vehicle and airspace inclusive of community specific knowledge derived from the Federal Aviation Administration (FAA) NextGen Urban Air Mobility (UAM) Concept of Operations (ConOps) version 1.0. The stakeholder requirements derived from the FAA UAM NextGen ConOps will form …

Improved Strain Gage Instrumentation Strategies For Rotorcraft Blade Measurements, Timothy S. Davis

Mechanical & Aerospace Engineering Theses & Dissertations

In this work, a new strategy is presented to wire, calibrate, and measure strain gages for rotor blade testing that will provide more information and is robust to individual gage loss. The additional information can be used in several ways. including reducing redundancy, offering rapid identification of damage locations, and in some cases reducing risk allowing tests to continue to collect calibrated data after one or more sensors have failed. This strategy replaces the classical four-gage full Wheatstone bridge with four separately wired quarter bridges that are combined into a full bridge in the data acquisition system using a calculated …

Conical Orbital Mechanics: A Rework Of Classic Orbit Transfer Mechanics, Cian Anthony Branco

Mechanical & Aerospace Engineering Theses & Dissertations

Simple orbital maneuvers obeying Kepler’s Laws, when taken with respect to Newton’s framework, require considerable time and effort to interpret and understand. Instead of a purely mathematical approach relying on the governing relations, a graphical geometric conceptual representation provides a useful alternative to the physical realities of orbits. Conic sections utilized within the full scope of a modified cone (frustum) were employed to demonstrate and develop a geometric approach to elliptical orbit transformations. The geometric model in-question utilizes the rotation of a plane intersecting the orbital frustum at some angle β (and the change in this angle) in a novel …

Numerical Analysis Of A Roadway Piezoelectric Harvesting System, Abdul Rahman Badawi

Mechanical & Aerospace Engineering Theses & Dissertations

Highways, streets, bridges, and sidewalks with heavy traffic dissipate a considerable amount of waste mechanical energy every day. Piezoelectric energy harvesting devices are a very promising technology that can convert the waste mechanical energy to clean and renewable energy to enhance the sustainability of infrastructures. Research efforts in large-scale energy harvesting have led to the advancement of piezoelectric devices to the point that large-scale implementation is starting to become more feasible. The energy harvested by these devices can be used in many ways such as providing heating or cooling, melting ice, monitoring structural conditions in bridges and tunnels, and powering …

The Effect Of Compaction Temperature And Pressure On Mechanical Properties Of 3d Printed Short Glass Fiber Composites, Pushpashree Jain Ajith Kumar Jain

Mechanical & Aerospace Engineering Theses & Dissertations

Among many thermoplastics that are used in engineering, polyamide 6 (nylon 6) is an extremely versatile engineering thermoplastic. Nylon filled with glass fibers has higher mechanical strength and high wear resistance than general purpose nylon. 3D printed composites, based on fused filament modeling, typically suffer from poor bead-to-bead bonding and relatively high void content, limiting their mechanical properties

This thesis explores the effect of compaction pressure and temperature on improving the mechanical properties of 3D printed composites. Engineering moduli in the printing and transverse to printing direction, as well as ultimate strength were measured using the tensile testing with Digital …

A Parametric Analysis Of A Turbofan Engine With An Auxiliary Bypass Combustion Chamber – The Turboaux Engine, Kaleab Fetahi

Mechanical & Aerospace Engineering Theses & Dissertations

A parametric study of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine is presented. The TurboAux engine is conceived as an extension of a low-bypass turbofan engine with an auxiliary bypass annular combustion chamber around the core stream. The study presented in this thesis is motivated by the need to facilitate clean secondary burning of fuel at temperatures higher than conventionally realized, from air exiting the low-pressure compressor. The parametric study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. Following that, the conventional turbofan and its mixing …

Detailed Modeling Of The Flash Hydrolysis Of Algae For Biofuel-Production In Comsol Multiphysics, Noah Joseph Legrand

Mechanical & Aerospace Engineering Theses & Dissertations

Algae-derived biofuels are being commercialized as an important renewable energy source. Like any new technology, conversion improvements are desired, including reductions in process complexity and better utilization of the entire microalgae feedstock. The Old Dominion Biomass Laboratory has focused on flash hydrolysis for algae biofuel production. That process involves rapidly heating algae and water mixed as a slurry to a subcritical state. Results from small-scale bench tests are promising, but process scale up is a challenge. Currently there exists a pilot laboratory scale system utilizing induction heating in order to reach controlled reaction temperatures with a reaction duration of 10 …

Parametric Study Of Residual Stresses In Wire And Arc Additive Manufactured Parts, Hisham Khaled Jamil Abusalma

Mechanical & Aerospace Engineering Theses & Dissertations

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective additive manufacturing process due to its capability to fabricate large metal parts with high deposition rate and low equipment cost. Although this method is gaining popularity in manufacturing industry, more research is needed to understand process parameters’ effects on residual stress (RS) distribution and part distortion. As such, a 3D thermo-elastic-plastic transient model was established in ABAQUS and employed to investigate the effect of process parameters such as the torch speed, the deposition power and the interlayer dwell time on RS distribution and distortion in WAAM part. The numerical model utilized …

Model Based Systems Engineering For A Venture Class Launch Facility, Walter Mcgee Taraila

Mechanical & Aerospace Engineering Theses & Dissertations

A study of Model-Based Systems Engineering (MBSE) applied to a small-lift launch facility is presented. The research uses Systems Modeling Language (SysML) products and functional diagrams to document the structure, controls, electrical power, hydraulic, safety mechanisms, software, and fluid ground systems on a launch pad. The research is motivated by the need to design complex systems with an unambiguous understanding that improves communication, quality, productivity, and reduces risk. A model is developed following the ISO/IEC-15288 technical process framework. The stakeholder requirements are defined and analyzed to provide traceability to individual systems and subsystems. An architectural design is realized and implemented …

Finite Element Analysis Investigation Of Hybrid Thin-Ply Composites For Improved Performance Of Aerospace Structures, Alana M. Zahn

Mechanical & Aerospace Engineering Theses & Dissertations

Commercial and private aircraft have a need for strong yet light materials in order to have the most ideal performance possible. This study looks at the use of thin-ply composite materials to improve the performance of aircraft structures by means of weight savings and/or strength increase when compared to laminates that are composed of exclusively standard-ply materials. In order to perform an investigation based solely on finite element analysis, validation efforts were performed using test data from open hole tension, open hole compression, notched tension, and notched compression specimens. Once the models were validated sufficiently, the same modeling practices were …

Energy Harvesting Using Flextensional Piezoelectric Energy Harvesters In Resonance And Off-Resonance Modes, Mohamed A. Shabara

Mechanical & Aerospace Engineering Theses & Dissertations

Energy harvesting technologies are integrated into various modern devices and systems. These systems include Artificial Intelligence (AI) systems, Internet of Things (IoT), various types of energy harvesters are integrated in many engineering applications such as automotive, aerospace and ocean engineering. In order to develop a fully functioning stand-alone system, it is essential to integrate it with a built in power source such as a battery or a power generator. Also, in many situations, city power sources might not be available. Therefore, reliable, renewable and sustainable local power generators are desired. Piezoelectric energy harvesting (PEH) technologies, which are piezoelectric material-based devices, …

Mechanism Of Compaction With Wrinkle Formation During Automatic Stitching Of Dry Fabrics And The Size Effect Of Compression Molded Discontinuous Fiber-Reinforced Composites, Anibal Benjamin Beltran Laredo

Mechanical & Aerospace Engineering Theses & Dissertations

With an ever-increasing demand for composites, more ways of manufacturing them are becoming popular and widely used. Stitching of dry fabrics is an efficient method for improving delamination resistance. Discontinuous fiber reinforced composites can be used as a lightweight alternative material for metals through a process of compression molding, which allows for complex shape manufacturing while offering structural grade mechanical properties.

This study demonstrates how the stitching of dry fabrics can be adapted to more complex surfaces. The consequences of stitching of curvilinear surfaces can result in defect formation. Therefore, to understand the physical formation of possible defects, experimental characterization …

Through-Thickness Reinforcement And Repair Of Carbon Fiber Based Honeycomb Structures Under Flexure And Tension Of Adhesively Bonded Joints, Aleric Alden Sanders

Mechanical & Aerospace Engineering Theses & Dissertations

Repair and reinforcement of composite honeycomb structures is an area of concern as higher demands are being placed on high strength, lightweight structural materials, such as carbon fiber reinforced plastics and corresponding honeycomb structures. A common issue with these structures is when a delamination in the facesheet may form and spread, leading to a failure scenario. An investigation of adding a through thickness reinforcement (TTR) to these structures at the sample level that undergo four-point-bending, tension, and joining methods is conducted throughout this thesis. The embedding of pultruded carbon fiber rods is found to be an ideal addition to composite …

Role Of Anisometric Particles In Ice-Templated Porous Ceramic Structure And Mechanical Properties, Mahesh Banda

Mechanical & Aerospace Engineering Theses & Dissertations

Open-cell macroporous ceramics have a significant impact on advancing various engineering endeavors such as bone-tissue engineering, lithium-ion batteries, filtration, thermal insulation, impact protection, etc. While pore orientation in conventional open-cell foams is random, in recent years, significant interest has grown in utilizing directionally porous ceramics in these applications to enhance performance. Ice-templating has emerged as a versatile technique that can synthesize directionally macroporous ceramics with low pore tortuosity. Although the fabrication is relatively straightforward, the challenge is that there are numerous variables associated with this technique, which can have significant effects on the final structure and macroscopic properties. As a …

Compaction And Residual Stress Modeling In Composite Manufactured With Automated Fiber Placement, Von Clyde Jamora

Mechanical & Aerospace Engineering Theses & Dissertations

Automated fiber placement is a state-of-the-art manufacturing process that allows for complex layup patterns and can quickly place, cut, and restart composite tows. However, with this type of manufacturing process layup defects are inevitable, and manufacturing defects propagate after curing. Process modeling is the considered approach for exploring the defect prediction. Two different but related works were conducted, which are the thermochemical and hyperelastic model and the residual deformation model. For the model before cooling, a hyperelastic model and a thermo-chemical were made to simulate the compaction and heat transfer. Temperature dependent properties that are a function of degree of …

Thermal Contact Resistance Measurement And Related Uncertainties, Amanda Elizabeth Stark

Mechanical & Aerospace Engineering Theses & Dissertations

Thermal contact resistance is an important parameter in detailed thermal analysis and design of aerospace systems. The ability to determine thermal contact resistance reliably can have a significant impact on the fidelity of thermal models—particularly for space applications. The 2004 NASA Langley Research Center thermal contact resistance test apparatus has been employed to evaluate two methods for inferring estimated interface surface temperatures so that thermal contact resistance can be calculated more accurately. The traditional method of extrapolation is a steady-state approach, while the new method utilizes inverse heat transfer techniques to account for inherent unsteadiness in these quasi-steady-state measurements. The …

A Study Of The Aeroacoustics Of Swept Propellers For Small Unmanned Aerial Vehicles, Arthur David Wiedemann

Mechanical & Aerospace Engineering Theses & Dissertations

In recent years, small unmanned aerial vehicles (UAVs) have increased in availability and use in both public and commercial sectors. This increased use of small UAVs or “drones” has the unfortunate consequence of introducing excessive noise into communities where they operate. Implementation of noise reduction methods is necessary if we wish to see expanded use of drones in public areas. With electric propulsion, the primary source of noise is the rotor/propeller used in contemporary multi-rotor configurations. In this thesis, the aerodynamics and acoustic behavior of various swept propellers is examined with computational and experimental methods.

A family of propeller geometries …

Effect Of The Physical Micro-Environment On Cell Adhesion And Force Exertion, Mohamad Eftekharjoo

Mechanical & Aerospace Engineering Theses & Dissertations

Physical characteristics of the microenvironment, such as geometry and stiffness, influence cell adhesion and contractile forces. Here, we determined how these physical factors influenced cell force exertion and adhesion in two specific contexts that have broad relevance.

Fibroblasts are cells in connective tissues that interact with a fibrous extracellular matrix (ECM) that have a predominantly one-dimensional (1D) (fibrillar) geometry. However, it has been unclear as to how the 1D nature of the fibrillar ECM influences the forces exerted by fibroblasts. Here, we used fibroblast cells adherent on fibronectin lines on polyacrylamide (PAA) gels of stiffness 13 and 45 kPa to …

Extension Of A Penalty Method For Numerically Solving Constrained Multibody Dynamic Problems, Troy Newhart

Mechanical & Aerospace Engineering Theses & Dissertations

Numerical analysis of constrained static and multibody dynamic systems has become an integral part of engineering analysis with the continued improvements in technology and software availability. Many methods currently exist for numerically solving constrained static and dynamic systems. The applicability of a penalty method for constrained static solutions is observed in many academic texts and papers. The appeal for using a penalty method in statics pertains to its ease of implementation, computational suitability, and accuracy. This thesis extends a static penalty method for use with constrained multibody dynamics to observe if the penalty method’s benefits are similar for a dynamics …

A Cfd Study Of Steady Fully Developed Laminar Flow Through A 90-Degree Bend Pipe With A Square Cross-Sectional Area, Subodh Sushant Toraskar

Mechanical & Aerospace Engineering Theses & Dissertations

Fluid flow through a closed curved conduit has always been a topic of extensive research, as it has many practical and industrial applications. The flow is generally characterized by a presence of secondary flow, vortical motions and pressure losses for different flow regimes. These observed irregularities may positively or negatively impact the flow. They are beneficial for cases where mixing of fluids is required, usually observed for multiphase flow regimes or detrimental for cases involving particles in the fluid. There are also instances where a particle-laden fluid transported through the curved pipe was directly related to corrosion- erosion related problems. …

Computational Analysis And Design Optimization Of Convective Pcr Devices, Jung Il Shu

Mechanical & Aerospace Engineering Theses & Dissertations

Polymerase Chain Reaction (PCR) is a relatively novel technique to amplify a few copies of DNA to a detectable level. PCR has already become common in biomedical research, criminal forensics, molecular archaeology, and so on. Many have attempted to develop PCR devices in numerous types for the purpose of the lab-on-chip (LOC) or point-of-care (POC). To use PCR devices for POC lab testing, the price must be lower, and the performance should be comparable to the lab devices. For current practices with the existing methods, the price is pushed up higher partially due to too much dependence on numerous developmental …

Unsupervised-Learning Assisted Artificial Neural Network For Optimization, Varun Kote

Mechanical & Aerospace Engineering Theses & Dissertations

Innovations in computer technology made way for Computational Fluid Dynamics (CFD) into engineering, which supported the development of new designs by reducing the cost and time by lowering the dependency on experimentation. There is a further need to make the process of development more efficient. One such technology is Artificial Intelligence. In this thesis, we explore the application of Artificial Intelligence (AI) in CFD and how it can improve the process of development.

AI is used as a buzz word for the mechanism which can learn by itself and make the decision accordingly. Machine learning (ML) is a subset of …

Endogenous Force Transmission Between Epithelial Cells And A Role For Α-Catenin, Sandeep Dumbali

Mechanical & Aerospace Engineering Theses & Dissertations

In epithelial tissues, epithelial cells adhere to each other as well as to the underlying extra-cellular matrix (ECM). E-cadherin-based intercellular junctions play an important role in tissue integrity. These junctions experience cell-generated mechanical forces via apparent adaptor proteins such as beta (β) catenin, alpha (α) catenin and vinculin. Abnormalities in these junctions may result in skin related diseases and cancers. Here, I devised methods to determine the endogenous intercellular force within cell pairs as well as in large epithelial islands. I further ascertained the factors that affect the level of inter-cellular tension.

Experiments with pairs of epithelial cells exogenously expressing …

Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles

Mechanical & Aerospace Engineering Theses & Dissertations

The aim of this thesis is to explore methods to reduce the noise impact of unmanned aerial vehicles operating within acoustically sensitive environments by flight control system augmentation. Two methods are investigated and include: (i) reduction of sound generated by vehicle speed control while flying along a nominal path and (ii) reduction of acoustic exposure by vehicle path control while flying at a nominal speed. Both methods require incorporation of an acoustic model into the flight control system as an additional control objective and an acoustic metric to characterize primary noise sources dependent on vehicle state. An acoustic model was …

Comparison Of Support Methods For Static Aerodynamic Testing And Validation Of A Magnetic Suspension And Balance System, Cameron K. Neill

Mechanical & Aerospace Engineering Theses & Dissertations

Magnetic suspension wind tunnels offer an alternative to traditional physical support methods. They allow for the collection of support interference free data and broader dynamic test capabilities than existing methods. Determination of dynamic aerodynamic characteristics is a crucial portion of the design of new re-entry capsules. A NASA initiative restored the 6-inch Magnetic Suspension and Balance System to support the design of a new MSBS for a supersonic wind tunnel. Before a new MSBS can be constructed, the characteristics of the current MSBS must be examined.

This thesis discusses the calibration and validation of the 6-inch MSBS. After calibration, three …

Off Axis Compressive Response Of Ice-Templated Ceramics, Rahul Kumar Jujjavarapu

Mechanical & Aerospace Engineering Theses & Dissertations

The off-axis compressive behavior of ice-templated ceramic was analyzed using experimental results and micro-mechanical model simulation. Ice-templated ceramics is a versatile processing technique used to manufacture anisotropic ceramic foam by exploiting the anisotropic growth characteristics and lamellar morphology. The ice-templating process results in processing-structure-property relationships determined by the microstructure. The processed alumina samples which were later manufactured by water jet machine from the freeze casting were tested under quasi-static off-axis loading conditions and were used to determine the mechanical properties of the material. Digital image correlation (DIC) was used to measure the strain response of ice-templated ceramic under off-axis loading. …

Estimation Of Arterial Wall Parameters Via Model-Based Analysis Of Noninvasively Measured Arterial Pulse Signals, Dan Wang

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation presents a model-based method for estimating arterial wall parameters from noninvasively measured arterial pulse signals via a microfluidic-based tactile sensor. The sensor entails a polydimethylsiloxane (PDMS) microstructure embedded with 5×1 transducer array built on Pyrex/Polyethylene terephthalate (PET) substrate. The arterial pulse causes a time-varying deflection on the top of the PDMS microstructure, which registers as a resistance change by the transducer at the site of the artery.

Owing to the time-harmonic nature of its radial motion, the arterial wall is modeled as a second-order dynamic system. By combining this dynamic model with a hemodynamic model of blood flow, …

Design And Manufacture Of An Inertial Cascade Impactor For Industrial Hygiene Purposes, Hector Joel Gortaire

Mechanical & Aerospace Engineering Theses & Dissertations

Inertial cascade impactors are devices commonly used for industrial hygiene and pharmaceutical studies. Their main purpose is to separate particulate matter suspended in aerosols according to their sizes, which can vary from over 10 µm to 0.5 µm. Their versatility and ease of operation make them suitable for on-site sampling; however, designing them requires a careful consideration of the different geometric parameters that characterize them.

In this thesis, a 5-stage inertial cascade impactor was designed, modelled, constructed, and tested. The main design parameter was the volumetric flow rate, 40 l/min, which was provided by a vacuum pump. By continuous iterations, …