Aerospace 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 …

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 …

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 = …

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 …

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 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 …

Avoiding Overrun Accidents On Contaminated Runways, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

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 …

The Part Count Tool (Pact) For Concept Selection, Tarang Parashar, Katie Grantham Lough, Robert B. Stone

Engineering Management and Systems Engineering Faculty Research & Creative Works

This paper presents a part count tool that automates the consideration of manufacturing cost during the conceptual design phase by predicting part count for a particular product concept. with an approximate number of parts per product in the conceptual design phase, the designer can estimate the cost associated with the product. on the basis of the cost, the designer can make changes according to budget requirements. the part count tool will also aid in ranking the design concepts by number of components for a product. This tool utilizes existing automated concept generation algorithms to generate the design concepts. It extracts …

Spatial Instability Of Electrically Driven Jets With Finite Conductivity And Under Constant Or Variable Applied Field, Saulo Orizaga, Daniel N. Riahi

Applications and Applied Mathematics: An International Journal (AAM)

We investigate the problem of spatial instability of electrically driven viscous jets with finite electrical conductivity and in the presence of either a constant or a variable applied electric field. A mathematical model, which is developed and used for the spatially growing disturbances in electrically driven jet flows, leads to a lengthy equation for the unknown growth rate and frequency of the disturbances. This equation is solved numerically using Newton’s method. For neutral temporal stability boundary, we find, in particular, two new spatial modes of instability under certain conditions. One of these modes is enhanced by the strength Ω of …

Grating Lobe Reduction In Aperiodic Linear Arrays Of Physically Large Antennas, William C. Barott, Paul G. Steffes

Publications

We present performance bounds obtained from the optimization of the sidelobe levels of aperiodic linear arrays. The antennas comprising these arrays are large compared to the distance between neighboring antennas, a case not addressed in previously published work. This optimization is performed in pattern-space and is applicable over a wide range of scan angles. We show that grating lobes can be suppressed even when the elemental antennas are several wavelengths in size, provided that the ratio of the antenna size to the average spacing between the antenna center-points does not exceed 80%.

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 …

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 …

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 …

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 …

The Potential Of Cubesat Networks, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "The Potential of CubeSat Networks" from November 17, 2009.

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 …

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 …

Contribution Based Priority Assessment In A Web-Based Intelligent Argumentation Network For Collaborative Software Development, Xiaoqing Frank Liu, Maithili Satyavolu, Ming-Chuan Leu

Computer Science Faculty Research & Creative Works

Decision making is an important aspect in a collaborative software development process which involves a complex process of conflict resolution. the priority of the participants plays a vital role in conflict resolution as the decision-making process involves many participants from multiple perspectives. the priority assessment methods used in the process so far are usually static in nature, i.e., the priorities of the participants remain constant throughout the decision-making process. in order to make the collaborative system closer to real world scenarios, we incorporate dynamic priority assessment into a web-Based collaborative system based on intelligent computational argumentation, which was developed in …

Small Satellites, Applications And Launch Opportunities, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Small Satellites, Applications and Launch Opportunities" from October 16, 2009.

Project: F.U.N.B.O.E. (Follow-Up Nucleate Boiling On-Flight Experiment), Getaway Special Team 2009

Education and Outreach

No abstract provided.

University Satellite Programs, 1982-2009, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "University Satellite Programs, 1982-2009" from October 5, 2009.

Third Grade Lesson Plan: Where Does Heat Come From?, Getaway Special Team 2009

Education and Outreach

No abstract provided.

Numerical Solutions For The Cawapi Configuration On Unstructured Grids At Usafa, United States, Scott A. Morton, David R. Mcdaniel, Russell M. Cummings

Aerospace Engineering

No abstract provided.

Lessons Learned From The Numerical Investigations On The Vfe-2 Configuration, Willy Fritz, Russell M. Cummings

Aerospace Engineering

The Second International Vortex Flow Experiment provided a variety of experimental data for a 65° delta wing with sharp and blunt/rounded leading edges. Flow measurements including forces and moments, surface pressures, Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. A number of test cases were chosen for simulation by seven numerical groups, and a summary of their results is presented here. The ability of computational fluid dynamics to predict such flow features as the dual primary vortex system found on the blunt leading edge configuration and a shock/vortex …

Shock Effects On Delta Wing Vortex Breakdown, Lucy A. Schiavetta, Okko J. Boelens, Simone Crippa, Russell M. Cummings, Willy Fritz, Ken J. Badcock

Aerospace Engineering

It has been observed that delta wings placed in a transonic freestream can experience a sudden movement of the vortex breakdown location as the angle of incidence is increased. The chapter reports on the use Computational Fluid Dynamics (CFD) to examine this behaviour in detail. The study shows that a shock-vortex interaction is responsible. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sensitivity of the breakdown location. Limited experimental data is available to supplement the CFD results in certain key respects, and the ideal synergy between CFD …

Numerical Solutions For The Vfe-2 Configuration On Unstructured Grids At Usafa, United States, Russell M. Cummings, Andreas Schϋtte

Aerospace Engineering

The numerical simulation of the flow for the VFE-2 configuration with rounded leading edges is presented. For the numerical simulation the Cobalt Code was used, which uses a cell-centered unstructured hybrid mesh approach. Several numerical results are presented for the steady RANS equations as well as for DES and DDES hybrid approaches. Within this paper the focus is related to the dual primary vortex flow topology, especially the sensitivity of the flow to angle of attack and Reynolds number effects. Reasonable results are obtained with both steady RANS and SA-DDES simulations. The results are compared and verified by experimental data, …

Fifth Grade Lesson Plan: Solid, Liquid, And Gas, Getaway Special Team 2009

Education and Outreach

No abstract provided.