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Articles 5371 - 5400 of 11138

Full-Text Articles in Engineering

A Performance And Visualization Study On Inlet Geometries Of A Cross-Flow Fan., Yoel Tanquero May 2017

A Performance And Visualization Study On Inlet Geometries Of A Cross-Flow Fan., Yoel Tanquero

Electronic Theses and Dissertations

A study was conducted to characterize the flow-field in the suction region of different inlet geometries of a cross-flow fan. The characterization was accomplished by correlating the static performance curves measured for each fan-inlet configuration to the streamline plot obtained using a particle tracking velocimetry (PTV) measurement system at three constant flow rates (25, 40, and 55 CFM). The PTV measurement system used was developed by the author and uses helium bubbles as tracers, an LED light sheet, a slow motion camera, and a Matlab program. Four inlet geometry design variables were defined and independently studied to evaluate the effect …

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Influence Of Relative Density And Microstructural Anisotropy On The Global Elastic Properties Of Cellular Structures, Justin Compton May 2017

Influence Of Relative Density And Microstructural Anisotropy On The Global Elastic Properties Of Cellular Structures, Justin Compton

Mechanical and Aerospace Engineering Theses - Archive

The favorable strength-to-weight ratio of cellular solids makes them ideal for structural applications. With the advent of additive manufacturing, the fabrication of complex cellular structures is becoming a reality. It is therefore necessary to understand the mechanical properties of cellular structures. The global mechanical properties of cellular structures are governed by geometry and therefore, differ from the mechanical properties of the base material from which they are constructed. In this study, finite element models are developed to explore the effective elastic properties of honeycomb structures for isotropic and anisotropic microstructural material properties. Finite element models are generated for regular, hexagonal …

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Frequency Tuning Of Vibration Absorber Using Topology Optimization, Swapnil Subhash Harel May 2017

Frequency Tuning Of Vibration Absorber Using Topology Optimization, Swapnil Subhash Harel

Mechanical and Aerospace Engineering Theses - Archive

A tuned mass absorber is a system for reducing the amplitude in one oscillator by coupling it to a second oscillator. If tuned correctly, the maximum amplitude of the first oscillator in response to a periodic driver will be lowered, and much of the vibration will be ’transferred’ to the second oscillator. The tuned vibration absorber (TVA) has been utilized for vibration control purposes in many sectors of Civil/Automotive/Aerospace Engineering for many decades since its inception. Time and again we come across a situation in which a vibratory system is required to run near resonance. In the past, approaches have …

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Numerical Investigation Of Vortex Generator Flow Control For External-Compression Supersonic Inlets, Ezgihan Baydar May 2017

Numerical Investigation Of Vortex Generator Flow Control For External-Compression Supersonic Inlets, Ezgihan Baydar

Mechanical and Aerospace Engineering Dissertations - Archive

Vortex generators (VGs) within external-compression supersonic inlets for Mach 1.6 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. Ramp and vane-type VGs were studied. The geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the …

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Integration Of Macro-Fiber Composite Material On A Low Cost Unmanned Aerial System, May Chong Chan May 2017

Integration Of Macro-Fiber Composite Material On A Low Cost Unmanned Aerial System, May Chong Chan

Doctoral Dissertations and Master's Theses

The development, deployment, and operation of Unmanned Aerial Systems (UAS) have grown exponentially in recent years and have provided researchers with the opportunity to gain hands-on experience with aircraft in a manner that was previously limited to institutions and companies with large budgets. This allows the generation and testing of UAS advanced technologies using low cost systems. The scope of this thesis does not aim to make vast improvements to the control strategy itself, but to expand upon previous UAV work carried out at Embry-Riddle by designing, implementing, and demonstrating a simulation environment for mechanical and Macro-Fiber Composite (MFC) actuated …

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Performance Analysis Of A Coaxial Helicopter In Hover And Forward Flight, Stanrich D. Fernandes May 2017

Performance Analysis Of A Coaxial Helicopter In Hover And Forward Flight, Stanrich D. Fernandes

Doctoral Dissertations and Master's Theses

The performance of a coaxial rotor system has been analyzed by establishing a proper basis of comparison between a conventional single rotor and coaxial rotor. An attempt has also been made to better understand the complicated aerodynamic interactions associated with coaxial rotor wakes by using a free-vortex methodology (FVM). The FVM is a Lagrangian-based wake convection methodology, which solves for the evolution of the vortical wake produced by the rotor blades under the influence of an external flow. The extent to which the two rotors interact with each other was found to be highly dependent on the inter-rotor spacing. To …

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Battery Centric Serial Hybrid Aircraft Performance And Design Space, Lenny Gartenberg May 2017

Battery Centric Serial Hybrid Aircraft Performance And Design Space, Lenny Gartenberg

Doctoral Dissertations and Master's Theses

The design space and flight envelope of a battery centric serial hybrid aircraft has been analytically derived. The formulation assumes cruising flight only and all energy available is used. The flight envelope can be generated for any conventional propeller driven serial hybrid aircraft. The advantageous combination of an electric motor and controllable-pitch electric propeller was also explored. The results are used to be able to control efficiency and noise at constant thrust and therefore constant airspeed. Manufacturer provided electric motor and propeller data is used for efficiency purposes. Since the electric motor is virtually silent compared to the propeller, published …

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Structural Design Of A Business Jet Winglet, Jaime Gutierrez May 2017

Structural Design Of A Business Jet Winglet, Jaime Gutierrez

Doctoral Dissertations and Master's Theses

Structural sizing of a winglet for the Falcon 10 was performed and is presented here. The aerodynamic profile of the winglet was taken from a previous study, which predicted an increase in range of 3.3% with an estimated weight increase of 52 kg. An investigation of the current structure layouts and materials used in the industry was conducted. Six loading cases were analyzed to identify the most critical for the winglet, found to be negative and positive sideslip and gust. A finite element model was developed and used to size the structure. A fabrication process and assembly is described and …

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Comparison Of Rans Modeling To Dual-Plane Piv Measurements Of The Turbulent Tip Vortex Trailed From A Hovering Rotor, Zachary Lietzau May 2017

Comparison Of Rans Modeling To Dual-Plane Piv Measurements Of The Turbulent Tip Vortex Trailed From A Hovering Rotor, Zachary Lietzau

Doctoral Dissertations and Master's Theses

Numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) equations were conducted to study the development and turbulent decay of the tip vortices in the wake produced by a hovering rotor. The computational results were compared to detailed, dual plane Particle Image Velocimetry (PIV) measurements of a turbulent tip vortex trailed from a single-bladed rotor. The work investigated both the required mesh resolution and most suitable turbulence closure models with rotational/curvature corrections by assessing their predictions of the tip vortex properties and the overall physical nature of the rotor wake. It was found that even when using a higher-order accurate central differencing …

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Extended Surface Heat Transfer Coefficients Via Endwall Temperature Measurements, Yogesh Pai May 2017

Extended Surface Heat Transfer Coefficients Via Endwall Temperature Measurements, Yogesh Pai

Doctoral Dissertations and Master's Theses

Short pins are used for internal cooling of the trailing edge in a gas turbine blade. A novel method is described in this thesis which helps in simplifying the experimental process used to obtain average heat transfer data on the pin surface, at the expense of additional post processing complexity. The method is based on a unique, analytical solution of the longitudinal conduction equation with internal heat generation, allowing computation of heat transfer rates via pin base temperature measurements via Temperature Sensitive Paint, or similar non-intrusive methods. Verification of this method is done with comparisons to the solution of infinite …

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The Effect Of Surface Materials And Morphology On Wingsuit Aerodynamics, Timothy Allen Sestak May 2017

The Effect Of Surface Materials And Morphology On Wingsuit Aerodynamics, Timothy Allen Sestak

Doctoral Dissertations and Master's Theses

This study examines the aerodynamic effects of the materials, textiles, and morphologies currently used in wingsuit design and construction. The experiment was a low-speed wind tunnel investigation using a rigid wing with an aspect ratio of 2, a NACA 4418 airfoil cross section and a smooth, polished painted surface as a baseline. The baseline wing was modified by covering the upper and lower surfaces with various textiles currently used in wingsuit construction. This study is the first step in continued research to design and build a wingsuit with superior glide performance compared to current designs. Surface textures and features on …

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The Issues And Complexities Surrounding The Future Of Long Duration Spaceflight, Solomon Miiro May 2017

The Issues And Complexities Surrounding The Future Of Long Duration Spaceflight, Solomon Miiro

Graduate Student Works

The Comprehensive Exam put forward by this proposal is intended to address the learning objectives covered by the Master of Aeronautical Science Degree with specializations in Aviation Aerospace Safety Systems and some limited aspects in Human Factors in Aviation Systems. This will be accomplished by researching the following topics: effects of long duration spaceflight on crew performance and functioning and the steps that should be taken to enable long term spaceflight mission crews in lieu of accomplishing important missions; a human factor analysis should current human-machine design interfaces be enhanced to make manual rendezvous and docking in space easier to …

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Multidisciplinary Shape Optimization Of A Composite Blended Wing Body Aircraft, Charles Maxwell Boozer May 2017

Multidisciplinary Shape Optimization Of A Composite Blended Wing Body Aircraft, Charles Maxwell Boozer

Theses and Dissertations

A multidisciplinary shape optimization tool coupling aerodynamics, structure, and performance was developed for battery powered aircraft. Utilizing high-fidelity computational fluid dynamics analysis tools and a structural wing weight tool, coupled based on the multidisciplinary feasible optimization architecture; aircraft geometry is modified in the optimization of the aircraft’s range or endurance. The developed tool is applied to three geometries: a hybrid blended wing body, delta wing UAS, the ONERA M6 wing, and a modified ONERA M6 wing. First, the optimization problem is presented with the objective function, constraints, and design vector. Next, the tool’s architecture and the analysis tools that are …

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2017 Spring Graduate Recognition Program, Propulsion Research Center, Robert Frederick May 2017

2017 Spring Graduate Recognition Program, Propulsion Research Center, Robert Frederick

PRC Graduate Recognition

This program includes the graduate recognition program for spring 2017. Includes photographs, upcoming events, recent publications, and student profiles.

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Flexsar Bistatic And Monostatic Circular Sar Collection, Chad Knight, Mark Jensen, Trevor Jewkes, Jacob Gunther May 2017

Flexsar Bistatic And Monostatic Circular Sar Collection, Chad Knight, Mark Jensen, Trevor Jewkes, Jacob Gunther

Space Dynamics Laboratory Publications

Bistatic SAR data has advantages and disadvantages compared to monostatic data. This papers examines a combined bistatic and monostatic SAR data collection. The airborne platform used a monostatic radar system with two transmit and two receive channels in a pulsed spotlight mode. Another receive-only system was placed on an elevated mountaintop. The mountaintop receive system had two receive channels. The airborne asset flew in a full circle around several targets, exercising a large range of bistatic geometries. Various SAR modes were collected, including single-channel, quad-channel, and along-track interferometry (ATI) data for monostatic and bistatic modalities. This paper focuses on the …

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Single Waypoint Zem/Zev Based Closed-Loop Controller Design For Rendezvous With A Rotating Target, Armando Alvarez Rolins May 2017

Single Waypoint Zem/Zev Based Closed-Loop Controller Design For Rendezvous With A Rotating Target, Armando Alvarez Rolins

Theses and Dissertations

The research presented in this thesis addresses a very specific kind of autonomous rendezvous procedure between two spacecraft in close proximity, namely that in which the chaser object is attempting to dock at a location on a rotating target which is tracing a circle perpendicular to the axis of rotation. The approaches that have been mentioned in literature which focus on this specific condition make use of offline optimization algorithms to plot the trajectory of the chaser and use closed-loop control to follow that trajectory. This method is computationally demanding and does not allow for feedback in the desired boundary …

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Takeoff And Landing Distance Measurement: An Evaluation Of Laser Altimetry For The Collection Of Absolute Aircraft Altitude, Christopher John Kennedy May 2017

Takeoff And Landing Distance Measurement: An Evaluation Of Laser Altimetry For The Collection Of Absolute Aircraft Altitude, Christopher John Kennedy

Theses and Dissertations

The measurement of takeoff and landing distance during flight testing of general aviation aircraft requires the accurate measurement of aircraft position over the ground and altitude up to 50 feet above surface elevation. Current methods of evaluating takeoff and landing distances include cinetheodolites, laser and radar trackers, and Differential Global Positioning Systems (DGPS). The use of laser altimetry to range altitude above the ground originated with military and agricultural aircraft. The AgLaser laser module was an infrared laser ranging unit designed for agricultural aircraft to gauge optimal spray height above a field. The AgLaser system has a stated accuracy of …

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Refurbished And 3d Modeled Thermal Vacuum Chamber, Lauren M. Glenn May 2017

Refurbished And 3d Modeled Thermal Vacuum Chamber, Lauren M. Glenn

Master's Theses

Spacecraft testing includes acoustics, vibrations, and thermal vacuum. Cal Poly’s Space Environments Lab is equipped with multiple vacuum chambers, but no thermal vacuum chamber. The purpose of this thesis is to incorporate an ATS Chiller system with the HVEC vacuum chamber so students are able to experiment with a thermal vacuum chamber. The ATS Chiller had leaky pipes that needed to be refurbished and a shroud was implemented to improve thermal capabilities of the system. The full system was able to reach temperatures as low as -38ºC and as high as 58ºC at a pressure of 10-6 Torr. The ATS …

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Actuator Disk Theory For Compressible Flow, Htet Htet Nwe Oo May 2017

Actuator Disk Theory For Compressible Flow, Htet Htet Nwe Oo

Master's Theses

Because compressibility effects arise in real applications of propellers and turbines, the Actuator Disk Theory or Froude’s Momentum Theory was established for compressible, subsonic flow using the three laws of conservation and isentropic thermodynamics. The compressible Actuator Disk Theory was established for the unducted (bare) and ducted cases in which the disk was treated as the only assembly within the flow stream in the bare case and enclosed by a duct having a constant cross-sectional area equal to the disk area in the ducted case. The primary motivation of the current thesis was to predict the ideal performance of a …

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Application Of Strand-Cartesian Interfaced Solver On Flows Around Various Geometries, Yushi Yanagita May 2017

Application Of Strand-Cartesian Interfaced Solver On Flows Around Various Geometries, Yushi Yanagita

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

This work examines the application of a high-order numerical method to strand-based grids to solve the Navier-Stokes equations. Coined "Flux Correction", this method eliminates error terms in the fluxes of traditional second-order finite volume Galerkin methods. Flux Correction is first examined for applications to the Reynolds-Averaged Navier-Stokes equations to compute turbulent flows on a strictly strand-based domain. Flow over three geometries are examined to demonstrate the method’s capabilities: a three-dimensional bump, an infinite wing, and a hemisphere-cylinder configuration. Comparison to results obtained from established codes show that the turbulent Flux Correction scheme accurately predicts flow properties such as pressure, velocity …

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Evaluation Of Flux Correction On Three-Dimensional Strand Grids With An Overset Cartesian Grid, Dalon G. Work May 2017

Evaluation Of Flux Correction On Three-Dimensional Strand Grids With An Overset Cartesian Grid, Dalon G. Work

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Simulations of fluid flows over complex geometries are typically solved using a solution technique known as the overset meshing method. The geometry is meshed using grid types appropriate to the local geometry in a patchwork fashion, rather than meshing the entire geometry with one type of mesh. The strand-Cartesian approach is a simplification of this process. While high-order accurate solvers on Cartesian grids are simple to implement, strand grids are usually restricted to second-order accuracy, resulting in poor quality solutions. Flux correction is a high-order accurate solution method, specifically designed for use on strand grids. The flux correction method on …

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Characterization Of The Thermal Resistance Of Grain Boundaries Of Cerium Oxide, Jesse Spackman May 2017

Characterization Of The Thermal Resistance Of Grain Boundaries Of Cerium Oxide, Jesse Spackman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Many materials are made up of small crystals, or grains. Grain boundaries are the interfaces between two grains and affect the flow of heat through the material. These interfaces serve to interfere with the energy carriers by scattering or disrupting them. Because of the negative effect these interfaces have on these energy carriers, they inhibit heat flow and act as thermal resistors. The thermal boundary resistance between two grains of the same material is sometimes referred to as the Kapitza resistance, although this term is also used to describe the thermal resistance between solid/solid interfaces of different materials or solid/liquid …

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Water Entry Impact Dynamics Of Diving Birds, Saberul Islam Sharker May 2017

Water Entry Impact Dynamics Of Diving Birds, Saberul Islam Sharker

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Plunge diving and surface diving are two main techniques used by seabirds for foraging purposes. While some plunge divers can dive into the water at very high speeds (24 m/s), surface divers do not. This study analyzes the free-surface impact of 3D printed bird head models with embedded accelerometers to determine why surface divers cannot dive safely at high speeds. The problem is investigated in the context of impact jerk where surface divers, unlike plunge divers, are found to experience non-dimensional jerk (J∗) values exceeding a safe limit. This approach portrays itself as an unconventional yet effective method …

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Mechanical Performance Of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics And Experiments, Muhammad Ziaur Rahman May 2017

Mechanical Performance Of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics And Experiments, Muhammad Ziaur Rahman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A micromechanical analysis of the representative volume element (RVE) of a unidirectional flax/jute fiber reinforced epoxy composite is performed using finite element analysis (FEA). To do so, first effective mechanical properties of flax fiber and jute fiber are evaluated numerically and then used in evaluating the effective properties of flax/jute/epoxy hybrid composite. Mechanics of Structure Genome (MSG), a new homogenization tool developed in Purdue University, is used to calculate the homogenized effective properties. Numerical results are compared with analytical solution based on rule of mixture, Halpin-Tsai as well as Tsai-Hahn equations. The effect of the volume fraction of the two …

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A Survey And Performance Analysis Of Orbit Propagators For Leo, Geo, And Highly Elliptical Orbits, Simon P. Shuster May 2017

A Survey And Performance Analysis Of Orbit Propagators For Leo, Geo, And Highly Elliptical Orbits, Simon P. Shuster

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

On-orbit targeting, guidance, and navigation relies on state vector propagation algorithms that must strike a balance between accuracy and computational efficiency. To better understand this balance, the relative position accuracy and computational requirements of numerical and analytical propagation methods are analyzed for a variety of orbits. For numerical propagation, several differential equation formulations (Cowell, Encke-time, Encke-beta, and Equinoctial Elements) are compared over a range of integration step sizes for a given set of perturbations and numerical integration methods. This comparison is repeated for two numerical integrators: a Runge-Kutta 4th order and a NLZD4/4. For analytical propagation, SGP4, which relies on …

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Intensity Control Of Individual Dbd Plasma Filament. I. Experiment With A Needle Electrode, M. C. Paliwoda, J. L. Rovey May 2017

Intensity Control Of Individual Dbd Plasma Filament. I. Experiment With A Needle Electrode, M. C. Paliwoda, J. L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Filamentary volume dielectric barrier discharge (DBD) produces patterned plasma structures that are currently being explored for reconfigurable metamaterial applications. In this work, the presence and intensity of a single filament (within an array of filaments) are controlled by biasing a low voltage needle electrode by less than 7% of the driving voltage. The current, voltage, and time-averaged normalized light intensity were measured while varying the needle voltage through self-biasing resistors. For a 7.5 kV, 3.2 kHz DBD in air, the needle-controlled filament intensity varies from 80% to 0% of the light intensity of surrounding filaments. When the biased voltage prevents …

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Intensity Control Of Individual Dbd Plasma Filament. Ii. Fundamental Physical Mechanism, M. C. Paliwoda, J. L. Rovey May 2017

Intensity Control Of Individual Dbd Plasma Filament. Ii. Fundamental Physical Mechanism, M. C. Paliwoda, J. L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Filamentary volume dielectric barrier discharge (DBD) produces patterned plasma structures that are currently being explored for reconfigurable metamaterial applications. Previous work has demonstrated control of the presence and intensity of a single DBD plasma filament (within an array of filaments) by biasing a low voltage needle electrode. The results were attributed to redistributed charge inside the DBD due to the modified electric field created by the needle electrode. In the present work, results from a 3D electrodynamic field simulation bolster this argument. Results show that increasing needle bias voltage causes changes in the transverse electric field structure, resulting in redistribution …

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Implementing Delay-Tolerant Networking At Morehead State University, Nathaniel J. Richard Apr 2017

Implementing Delay-Tolerant Networking At Morehead State University, Nathaniel J. Richard

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Nathaniel J. Richard on April 28, 2017.

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Flying Simple Experiments In Space, Robert J. Twiggs Apr 2017

Flying Simple Experiments In Space, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Flying Simple Experiments in Space" from April 28, 2017.

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Study Of Custom Tool Control In Aviation And Aerospace And Selection Of Materials And Manufacturing Process, Ethan C. Rowley Apr 2017

Study Of Custom Tool Control In Aviation And Aerospace And Selection Of Materials And Manufacturing Process, Ethan C. Rowley

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Business and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Ethan C. Rowley on April 27, 2017.

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