Engineering Commons^™

Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall

Theses and Dissertations

This study quantified the effects of discrete wall-based film cooling in a rocket with curved walls. Simulations and experiments showed decreasing with wall radius of curvature, holding jet diameter constant, improves net heat flux reduction (NHFR) and adiabatic effectiveness (η) for 90˚ compound injected cylindrical jets, though η is reduced at the highest curvature. NHFR and η improved further with a high favorable stream-wise pressure gradient (K=2.1x10^-5) at all tested blowing ratios, but were affected little by a high density ratio (DR=1.76) using carbon dioxide as the coolant. Experiments were run at a Reynolds number of 31K and …

Flow Visualization Study Of Passive Flow Control Features On A Film-Cooled Turbine Blade Leading Edge, Daniel R. Carroll

Theses and Dissertations

A flow visualization study was conducted on a model of a film-cooled turbine blade leading edge in a closed-loop water channel at Re_D = 30k. The model consisted of an 8.89 cm diameter half-cylinder with flat afterbody joined at the ninety degree point. A single radial coolant hole (d_c / D = 0.054) drilled 21.5° from the stagnation line, angled 20° to the surface and 90° to the flow direction generated a coolant jet transverse to the freestream. Water channel testing assessed the hydrodynamic effects of 16 passive flow control features, to include a variety of …

Fatigue Behavior Of An Advanced Sic/Sic Composite At Elevated Temperature In Air And In Steam, Devon T. Christensen

Theses and Dissertations

The fatigue behavior of an advanced Silicon Carbide/Silicon Carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1200 ˚C in laboratory air and in steam environments. The composite consisted of a SiC matrix reinforced with Boron Nitride (BN) coated Hi-Nicalon fibers woven into eight-harness-satin (8HS) weave plies. Tensile stress-strain behavior and tensile properties were also evaluated at 1200 ˚C. Tension-tension fatigue tests were conducted in both laboratory air and in steam at 1200 ˚C at frequencies of 0.1 Hz, 1.0 Hz, and 10 Hz. The tension-tension fatigue tests had a ratio of minimum stress to maximum stress of R = …

Laser-Induced Fluorescence And Synthetic Jet Fuel Analysis In The Ultra Compact Combustor, Aaron C. Drenth

Theses and Dissertations

The Ultra-Compact Combustor (UCC) is currently under investigation at the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory’s Propulsion Directorate. The combustor is a small-scale, axi-symmetric, atmospheric pressure, laboratory combustor with an outer circumferential cavity in which the flame is stabilized by a highly accelerated swirled flow. UCCs will enable aero gas turbine reheat cycle engines and significantly shorten conventional aero gas turbine engines. The experiments of this work utilized the AFIT small-scale combustion diagnostics facility, investigating a sector model of the UCC. The research objectives were to perform an addition to the COAL lab laser diagnostic …

Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert

Theses and Dissertations

This research examines the physical and electrical processes involved in lifecycle failure of Microelectromechanical (MEMS) Radio-Frequency (RF) cantilever beam ohmic contact switches. Failures of these switches generally occur at the contact, but complete details of performance of microcontacts are difficult to measure and have not been previously reported. This study investigated the mechanics of microcontact behavior by designing and constructing a novel experimental setup. Three representative contact materials of varying microstructure (Au, Au5%Ru, Au4%V₂O₅) were tested and parameters of contact during cycling were measured. The Au4%V₂O₅, a dispersion strengthened material developed at …

Flow Measurements Using Particle Image Velocimetry In The Ultra Compact Combustor, Levi M. Thomas

Theses and Dissertations

Velocity measurements were performed using the Particle Image Velocimetry (PIV) technique on the Ultra Compact Combustor (UCC) test rig at the Air Force Institute of Technology (AFIT). Velocity patterns and time-averaged turbulence statistics were calculated for data taken with the UCC burning hydrogen fuel in the straight cavity vane and curved cavity vane configurations. The equivalence ratio was varied from 0.7 to 1.5, while the ratio of cavity air to main air was varied from 5% to 20% in testing performed on the straight vane configuration. Spanwise velocity was observed to decrease linearly with distance from the cavity vane over …

A Study Of Nonlinear Combustion Instability, Eric J. Jacob

Doctoral Dissertations

Combustion instability (CI) has been persistent in all forms of propulsion since their inception. CI is characterized by pressure oscillations within the propulsion system. If even a small fraction of the dense energy within the system is converted to acoustic oscillations the system vibrations can be devastating. The coupling of combustion and fluid dynamic phenomena in a nonlinear system poses CI as a significant engineering challenge.

Drawing from previous analysis, second order acoustic energy models are taken to third order. Second order analysis predicts exponential growth. The addition of the third order terms capture the nonlinear acoustic phenomena (such as …

Removal Of Biofilm Through Controlled Cavitation, Mathew Chackalackal Mathew

Master's Theses - Daytona Beach

Human kind is poised to take the next "giant step" in space exploration, the manned mission to Mars, among other things. But before any plans for such long term habitation on an alien planet, there has to be consideration towards prevention and removal of bacterial contamination. Bacterial contamination or rather degradation of materials was considered of negligible importance. Bacterial degradation can be serious for long-term manned space mission, more so because there is no way to obtain quick replacements. For such conditions, a new innovative way of bacterial removal has been proposed wherein the bacteria is removed with no damage …

Interim Access To The International Space Station, Tyson Karl Smith

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis evaluates mission scenarios using the existing Evolved Expendable Launch Vehicles for delivering the Crew Exploration Vehicle to the International Space Station. The Space Shuttle is scheduled to retire in the year 2011 and the Ares I is being developed to replace it. With its current schedule, the earliest that the Ares I will become fully operational is 2016. The configurations in this thesis are presented to narrow the gap in which the USA does not have direct access to the International Space Station. They also present "buy down" options for the USA human space operations, if the current …

A Domain-Specific Design Tool For Verifying Spacecraft System Behavior, Sravanthi Venigalla

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this report we present a graphical tool, Behavioral Analysis of Spacecraft Systems (BASS), that can be used by spacecraft designers to perform system-level behavioral analysis of small satellites. The domain-specific spacecraft meta-model is created in the visual modeling tool Generic Modeling Environment (GME) such that spacecraft designs created using the meta-model appear familiar to the spacecraft designers. Users can model scenarios that are to be verified for the design in BASS. The graphical models are assigned formal semantics facilitating the creation of formally verifiable spacecraft models. The C++ application that translates the modeling objects to equivalent mathematical representation of …

Embedded Spacecraft Thermal Control Using Ultrasonic Consolidation, Jared W. Clements

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Research has been completed in order to rapidly manufacture spacecraft thermal control technologies embedded in spacecraft structural panels using ultrasonic consolidation. This rapid manufacturing process enables custom thermal control designs in the time frame necessary for responsive space. Successfully embedded components include temperature sensors, heaters, wire harnessing, pre-manufactured heat pipes, and custom integral heat pipes. High conductivity inserts and custom integral pulsating heat pipes were unsuccessfully attempted. This research shows the viability of rapid manufacturing of spacecraft structures with embedded thermal control using ultrasonic consolidation.

An Autonomous Unmanned Aerial Vehicle-Based Imagery System Development And Remote Sensing Images Classification For Agricultural Applications, Yiding Han

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This work concentrates on the topic of remote sensing using a multispectral imag-ing system for water management and agriculture applications. The platform, which is alight-weight inexpensive runway-free unmanned aerial vehicle (UAV), namely, AggieAir, ispresented initially. A major portion of this work focuses on the development of a light-weight multispectral imager payload for the AggieAir platform, called GhostFoto. Theimager is band-recongurable, covering both visual red, green, and blue (RGB) and nearinfrared (NIR) spectrum, and interfaced with UAV on-board computer. The developmentof the image processing techniques, which are based on the collected multispectral aerialimages, is also presented in this work. One application …

Integral Formulation Of The Compressible Flowfield In Solid Rocket Motors, Michel Henry Akiki

Masters Theses

In this thesis, a semi-analytical formulation is provided for the rotational, steady, inviscid, compressible motion in a solid rocket motor that is modeled as a slender porous chamber. The analysis overcomes some of the deficiencies encountered in previous work on the subject. The method that we employ consists of reducing the problem’s mass, momentum, energy, ideal gas, and isentropic relations into a single integral equation that can be solved numerically. Furthermore, Saint-Robert’s power law is used to link the pressure to the sidewall mass injection rate. At the outset, results are presented for the axisymmetric and planar porous chambers and …

Development And Testing Of A Self-Contained, Portable Instrumentation System For A Fighter Pilot Helmet, Michael Anthony Kamp

Masters Theses

A self-contained, portable, inertial and positional measurement system was developed and tested for an HGU-55 model fighter pilot helmet. The system, designated the Portable Helmet Instrumentation System (PHIS), demonstrated the recording of accelerations and rotational rates experienced by the human head in a flight environment. A compact, self-contained, “knee-board” sized computer recorded these accelerations and rotational rates during flight. The present research presents the results of a limited evaluation of this helmet-mounted instrumentation system flown in an Extra 300 fully aerobatic aircraft. The accuracy of the helmet-mounted, inertial head tracker system was compared to the aircraft-mounted referenced system. The ability …

An Experimental Analysis Of The Laminar Separation Bubble At Low Reynolds Numbers, Karla Marie Swift

Masters Theses

This paper is an investigation into the laminar separation bubble that frequently plagues airborne vehicles operating in the low Reynolds number regime – experimentally found to be typically present in flows with Reynolds numbers below 10⁶ (Lissaman 1983). The specific application driving the present investigation is the fixed wing performance of unmanned micro air vehicles (MAVs), defined by their maximum chord length of 6 inches and current cruising speeds of 10-20 meters per second (Mueller 2001). A basic generic model was chosen for this investigation: a circular arc (section of 16 inch diameter PVC pipe) with sharp leading and …

Computational Investigations Of Characteristic Performance Improvements For Subkilogram Laser Micropropulsion, Richard Joel Thompson

Masters Theses

Experimental investigations have evaluated the feasibility of using laser-driven plasma microthrusters for small-thrust, high-specific-impulse space maneuvers, particularly for micro- and nanosatellite missions. Recent work made use of the Mach2 hydromagnetics code for the construction of an adequate computational model of the micro-thruster opera- tion. This thesis expounds on this previous work by extending the computational modeling capabilities, allowing for the determination of plasma plume properties and characteristic performance assessment of the microthruster; this allows for further computational investi- gation of the performance improvements achieved by new design considerations. Two par- ticular design changes are implemented and measured: (i) the simulation …

Simulation, Synthesis, And Characterization Of Hydrogels And Nanocomposite Gels., Kamleshkumar J. Suthar

Dissertations

Stimuli-responsive gels are three-dimensional, cross-linked polymeric materials that undergo large physical change in response to the environmental stimuli, like temperature, pH, electrical potential, and irradiation. Ferrogels are colloidaldispersion of magnetic nanoparticles in the hydrogel network. The magnetic nanoparticles are attached to the polymeric network by different adhesive forces; as a result, it becomes sensitive to the applied magnetic field.

The main objective of this research is the simulation, synthesis, and characterization of the hydrogel and ferrogel. Simulation of the hydrogel response was performed for various environmental stimuli using a multiphysics finite element analysis software, COMSOL. The pH and electrical response …

Multiple Axisymmetric Solutions For Axially Traveling Waves In Solid Rocket Motors, Nadim Yaacoub Zgheib

Masters Theses

In this article, we consider the vorticoacoustic flowfield arising in a rightcylindrical porous chamber with uniform sidewall injection. Such configuration is often used to simulate the internal gaseous environment of a solid rocket motor (SRM). Assuming closed-closed acoustic conditions at both fore and aft ends of the domain, the introduction of small disturbances in the mean flow give rise to an axially traveling vortico-acoustically dominated wave structure that our study attempts to elucidate. Although this problem has been formulated before, it is reconsidered here in the context of WKB perturbation expansions in the reciprocal of the crossflow Reynolds number. This …

Effects Of Delamination On Composite Sandwich Structures Under Static And Fatigue Loading, Eugene Everett Eswonia

Master's Theses

This thesis will present the experimental and numerical analysis of composite sandwich structures under monotonic and fatigue loading. The sandwich skins were made of fiberglass and the core used was a closed cell PVC foam. Initial delaminations were introduced into the sandwich structures during manufacturing to see the effect of delamination size on the ultimate strength and monotonic fracture. Fiberglass rods, called shear keys, added to the foam core to determine whether or not they increased the strength of the test specimens. Furthermore, shear key locations were also varied and their effects noted. The fixed rate static behavior for all …

Numerical Simulation Of Mode Transition In A Hydrogen-Fueled Scramjet, Manan Ajay Vyas

Master's Theses - Daytona Beach

The Wind-US computational fluid dynamics (CFD) flow solver was used to simulate dual-mode direct-connect ramjet/scramjet engine flowpath tests conducted in the University of Virginia (UVa) Supersonic Combustion Facility (SCF). The objective was to develop a computational capability within Wind-US to aid current hypersonic research and provide insight to flow as well as chemistry details that are not resolved by instruments available. Computational results are compared with experimental data to validate the accuracy of the numerical modeling. These results include two fuel-off non-reacting and eight fuel-on reacting cases with different equivalence ratios, split between one set with a clean (non-vitiated) air …

Aerodynamic Performance Enhancement Of A Naca 66–206 Airfoil Using Supersonic Channel Airfoil Design, David Michael Giles

Master's Theses

Supersonic channel airfoil design techniques have been shown to significantly reduce drag in high-speed flows over diamond shaped airfoils by Ruffin and colleagues. The effect of applying these techniques to a NACA 66-206 airfoil is presented. The design domain entails channel heights of 8-16.6% thickness-to-chord and speeds from Mach 1.5-3.0. Numerical simulations show an increase in the lift-to-drag ratio for airfoils at Mach 2.5 at a 35,000-ft altitude with a 12% channel height geometry showing a benefit of 17.2% at 6-deg angle of attack and a sharp channel leading edge. Wave drag is significantly reduced while viscous forces are slightly …

An Analytical Investigation Of Natural Frequency For A Symmetric Composite Box-Beam With Thermal Effects, Lakshmi Narayana Sanjeev Chitikela

Master's Theses - Daytona Beach

The main purpose of the following analysis is to develop an analytical method for determining the natural frequency of a symmetric composite box-beam subjected to temperature gradient. A set of coupled partial differential equations of motion is obtained by means of small defection theory and D'Alembert's method. The Smith and Chopra stiffness matrix is used in the governing equations of motion and an appropriate MATLAB® code has been written to solve for the stiffness matrix elements of the box-beam. The resulting governing equations of motion are solved to obtain the natural frequencies of the box-beam in flap and lag directions …

Compression After Impact Load Prediction In Graphite/Epoxy Laminates Using Acoustic Emission And Artificial Neural Networks, Anthony Michael Gunasekera

Master's Theses - Daytona Beach

The purpose of this research was to investigate the effectiveness of artificial neural networks (ANNs) in predicting the compression after impact (CAI) load of graphite/epoxy laminates from acoustic emission (AE) nondestructive testing (NDT) data. Thirty-four 24-ply bidirectional woven cloth laminate coupons were constructed and impacted at various energy levels ranging from 8 to 20 Joules, generating barely visible impact damage (BVID). Acoustic emission data were acquired as the coupons were compressed to failure. Not having been analyzed by previous experimenters, several noise tests were also performed to determine the impact of external noise on acoustic emission data during testing. Once …

Determination Of Stability And Control Derivatives For A Modern Light Composite Twin Engine Airplane, Monica M. Londono

Master's Theses - Daytona Beach

To develop and compare full envelope stability and control derivatives and their associated errors for a modern light composite twin engine airplane from flight test data and digital DATCOM (Data Compendium). This development is to serve three purposes 1) to provide data for validation of newer analytical techniques such as Computational Fluid Dynamics (CFD), 2) to provide public domain static and dynamic stability and control derivatives for a modern twin engine airplane, 3) to analyze the relationship between test design and error for both output error and equation error methods.

A flight test program was conducted on a Diamond Twin …

The Effect Of Pilot And Air Traffic Control Experiences & Automation Management Strategies On Uas Mission Task Performance, Christopher J. Reynolds

Master's Theses - Daytona Beach

Unmanned aircraft are relied on now more than ever to save lives and support the troops in the recent Operation Enduring Freedom and Operation Iraqi Freedom. The demands for UAS capabilities are rapidly increasing in the civilian sector. However, UAS operations will not be carried out in the NAS until safety concerns are alleviated. Among these concerns is determining the appropriate level of automation in conjunction with a suitable pilot who exhibits the necessary knowledge, skills, and abilities to safely operate these systems.

This research examined two levels of automation: Management by Consent (MBC) and Management by Exception (MBE). User …

Flight Regime And Maneuver Recognition For Complex Maneuvers, Jerome H. Travert

Master's Theses - Daytona Beach

The purpose of this study is to demonstrate capability of flight regime recognition during complex maneuvers flown in a fixed wing airplane using measured data from an Inertial Measurement Unit (IMU). Flight Regime Recognition (FRR) is required for numerous applications in the aerospace and aviation industry, including the determination of loads for stress and strain analysis. It can also be used in recreational aviation for maneuver recognition, for example in aerobatics.

This study uses a flight simulator to generate representative flight data that is parsed by a specifically developed algorithm into appropriate flight regimes. This algorithm is a filter technique …

Precision Navigation Using Pre-Georegistered Map Data, Frederick C. Webber

Theses and Dissertations

Navigation performance in small unmanned aerial vehicles (UAVs) is adversely affected by limitations in current sensor technology for small, lightweight sensors. Because most UAVs are equipped with cameras for mission-related purposes, it is advantageous to utilize the camera to improve the navigation solution. This research improves navigation by matching camera images to a priori georegistered image data and combining this update with existing image-aided navigation technology. The georegistration matching is done by projecting the images into the same plane, extracting features using the techniques Scale Invariant Feature Transform (SIFT) [5] and Speeded-Up Robust Features (SURF) [3]. The features are matched …

Least-Squares, Continuous Sensitivity Analysis For Nonlinear Fluid-Structure Interaction, Douglas P. Wickert

Theses and Dissertations

A least-squares, continuous sensitivity analysis method is developed for transient aeroelastic gust response problems to support computationally efficient analysis and optimization of aeroelastic design problems. A key distinction between the local and total derivative forms of the sensitivity system is introduced. The continuous sensitivity equations and sensitivity boundary conditions are derived in local derivative form which is shown to be superior for several applications. The analysis and sensitivity problems are both posed in a first-order form which is amenable to a solution using the least-squares finite element method. Several example and validation problems are presented and solved, including elasticity, fluid, …

Pulsed Film Cooling On A Turbine Blade Leading Edge, James L. Rutledge

Theses and Dissertations

Unsteadiness in gas turbine film cooling jets may arise due to inherent unsteadiness of the flow through an engine or may be induced as a means of flow control. The traditional technique used to evaluate the performance of a steady film cooling scheme is demonstrated to be insufficient for use with unsteady film cooling and is modified to account for the cross coupling of the time dependent adiabatic effectiveness and heat transfer coefficient. The addition of a single term to the traditional steady form of the net heat flux reduction equation with time averaged quantities accounts for the unsteady effects. …

F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Joseph S. Browning

Theses and Dissertations

Buffet-induced vibrations can have a disastrous impact on aircraft structures. Early attempts at combating buffet vibrations included passive methods such as structural enhancements and leading edge fences. Active methods have shown greater promise, including active airflow control, control surface modulation, and active structural control using piezoelectric actuators. Surface mounted piezoelectric actuators impart directional strain reducing the negative effects associated with harmful vibration. The Block-15 F-16 ventral fin represents an aircraft structure prone to failure when subjected to the buffet field from the wake of a LANTIRN pod. This research takes advantage of the susceptibility to buffet vibration of the Block …