Aerospace Engineering Commons^™

Hydrogen Fuel Cell Analysis: Lessons Learned From Stationary Power Generation Final Report, Scott E. Grasman, John W. Sheffield, Fatih Dogan, Sunggyu Lee, Umit O. Koylu, Angie Rolufs

Materials Science and Engineering Faculty Research & Creative Works

This study considered opportunities for hydrogen in stationary applications in order to make recommendations related to RD&D strategies that incorporate lessons learned and best practices from relevant national and international stationary power efforts, as well as cost and environmental modeling of pathways. The study analyzed the different strategies utilized in power generation systems and identified the different challenges and opportunities for producing and using hydrogen as an energy carrier. Specific objectives included both a synopsis/critical analysis of lessons learned from previous stationary power programs and recommendations for a strategy for hydrogen infrastructure deployment. This strategy incorporates all hydrogen pathways and …

Adverse Elevator Effect In Landing Flare, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Women In The Aviation Industry, Maureen N. Mutisya

Senior Honors Theses

The Aviation industry has developed extensively since its establishment by the Wright Brothers in 1903. Over time, the highly male-dominated industry experienced significant changes to incorporate female aviators. Determined women initiated this process through participating in the aircraft engineering sector and pursuing careers as pilots. However, these women faced various challenges, which resulted in setbacks to their effective growth in the industry. In fact, vital issues encountered in the past are still present and often overlooked in today’s aviation industry. Therefore, identifying these problems and proposing solutions with effective corrective measures is necessary to increase and motivate female pilots globally.

Programs With Rockets, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs on "Programs with Rockets" from April 5, 2010.

Experimental Development Of Compressor And Turbine Performance Maps For Turbomachinery, Michael W. Green

Aerospace Engineering

Turbomachinery performance maps are used to reveal the on and off design performance of compressors and turbines. These maps plot the component’s pressure ratio versus the corrected flow rate for multiple engine rotor speeds. In this experiment, a Boeing T50-BO-8A converted turbojet engine was operated at a wide variety of rotor speeds with orifice plates of different sizes to vary the flow rate. The corrected flow rate through the turbojet ranged from 1.32 to 2.55 lb/s. The pressure ratios for the compressor and turbine ranged from 2.0 to 4.3 and from 1.7 to 4.3, respectively. The resulting performance maps showed …

Section Abstracts: Aeronautical And Aerospace Sciences

Virginia Journal of Science

Abstracts of the Aeronautical and Aerospace Science Section for the 88th Annual Meeting of the Virginia Academy of Science, May 20-21, 2010, James Madison University, Harrisonburg, VA.

Neural Network Fatigue Life Prediction In Notched Aluminum Specimens From Acoustic Emission Data, Muhammed Arif Okur

Master's Theses - Daytona Beach

This purpose of this research was to identify fatigue crack growth and predict failure for 7075-T6 aluminum notched bars under uniaxial tensile loading using acoustic emission (AE) data. The experiments performed in this study extend the results obtained by previous researchers who used maximum cyclic loads of 4,000, 3,000, and 2,000 pounds at a stress ratio of R = 0.0 and a frequency of 1 Hz to perform the fatigue tests. For this research the cyclic load remained at 2,000 pounds, but an additional ten specimens were tested in order to increase the amount of AE data available to the …

Stability Of Fully Nonlinear Stokes Waves On Deep Water: Part 1. Perturbation Theory, Shahrdad Sajjadi, David L. Ross

Publications

We consider a full set of harmonics for the Stokes wave in deep water in the absence of viscosity, and examine the role that higher harmonics play in modifying the classical Benjamin-Feir instability. Using a representation of the wave coefficients due to Wilton, a perturbation analysis shows that the Stokes wave may become unbounded due to interactions between the N^th harmonic of the primary wave train and a set of harmonics of a disturbance. If the frequency of the n^th harmonic is denoted Ꙍ_n = Ꙍ(1 ± ꭉ) then instability will occur if

√2 k n^{n …}

Non Bayesian Conditioning And Deconditioning, Jean Dezert, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

In this paper, we present a Non-Bayesian conditioning rule for belief revision. This rule is truly Non-Bayesian in the sense that it doesn’t satisfy the common adopted principle that when a prior belief is Bayesian, after conditioning by X, Bel(X|X) must be equal to one. Our new conditioning rule for belief revision is based on the proportional conflict redistribution rule of combination developed in DSmT (Dezert-Smarandache Theory) which abandons Bayes’ conditioning principle. Such Non-Bayesian conditioning allows to take into account judiciously the level of conflict between the prior belief available and the conditional evidence. We also introduce the deconditioning problem …

Reducing Orbit Covariance For Continuous Thrust Spacecraft Transfers, Scott Zimmer, Oscar Ocampo, Robert H. Bishop

Mechanical Engineering Faculty Research and Publications

The calculus of variations is used to develop the necessary theory and derive the optimality conditions for a spacecraft to transfer between a set of initial and final conditions, while minimizing a combination of fuel consumption and a function of the estimation error covariance matrix associated with the spacecraft state. The theory is developed in a general manner that allows for multiple observers, moving observers, covariance associated with an arbitrary frame, a wide variety of observation types, multiple gravity bodies, and uncertainties in the spacecraft equations of motion based on the thrusting status of the engine. A series of example …

High Order Finite Elements For Lagrangian Computational Fluid Dynamics, Truman Everett Ellis

Master's Theses

A general finite element method is presented to solve the Euler equations in a Lagrangian reference frame. This FEM framework allows for separate arbitrarily high order representation of kinematic and thermodynamic variables. An accompanying hydrodynamics code written in Matlab is presented as a test-bed to experiment with various basis function choices. A wide range of basis function pairs are postulated and a few choices are developed further, including the bi-quadratic Q2-Q1d and Q2-Q2d elements. These are compared with a corresponding pair of low order bi-linear elements, traditional Q1-Q0 and sub-zonal pressure Q1-Q1d. Several test problems are considered including static convergence …

Analysis Of Helicopter Downwash/Frigate Airwake Interaction Using Statistically Designed Experiments, Yavuz Nacakli

Mechanical & Aerospace Engineering Theses & Dissertations

A research program to investigate helicopter downwash/frigate airwake interaction has been initiated using a statistically robust experimental program featuring Design of Experiments. Engineering analysis of the helicopter/frigate interface is complicated by the fact that two flowfields become inherently coupled as separation distance decreases. The final objective of this work is to develop experimental methods to determine when computer simulations need to include the effects of a coupled flowfield versus using a simplified representation by superposing the velocity fields of the individual flowfields. The work presented was performed in the Old Dominion University Low Speed Wind Tunnel using a simplified 1/50 …

Numerical Simulation Of A Liquid Jet Atomization And Break-Up Using Ansys-Cfx 12.0, Yash Akhil Bhatt

Master's Theses - Daytona Beach

Break-up and atomization characteristics of JetA liquid fuel were investigated numerically. The results have been compared to various experimental results to evaluate the accuracy of the numerical model. The CFD code ANSYS-CFX 12.0 was used to carry out the steady state analysis at different time scales. A comparison between the atomization characteristics of a pressure jet atomizer and an air-blast atomizer is shown. By employing a Lagrangian particle tracking method to track the path of the liquid particles, the liquid jet/spray phenomena was studied in light of low and high back pressure environments. The 'BLOB' primary atomization model and the …

Acoustic Emission Fatigue Crack Monitoring Of A Simulated Aircraft Fuselage Structure, Jeremy James Lucas

Doctoral Dissertations and Master's Theses

The purpose of this research was to replicate the fatigue cracking that occurs in aircraft placed under loads from cyclical compression and decompression. As a fatigue crack grows, it releases energy in the form of acoustic emissions. These emissions are transmitted through the structure in waves, which can be recorded using acoustic emission (AE) transducers. This research employed a pressure vessel constructed out of aluminum and placed under cyclical loads at 1 Hz in order to simulate the loads placed on an aircraft fuselage in flight. The AE signals were recorded by four resonant AE transducers. These were placed on …

Hybrid Intelligent Optimization Methods For Engineering Problems, Yasin Volkan Pehlivanoglu

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of optimization is to obtain the best solution under certain conditions. There are numerous optimization methods because different problems need different solution methodologies; therefore, it is difficult to construct patterns. Also mathematical modeling of a natural phenomenon is almost based on differentials. Differential equations are constructed with relative increments among the factors related to yield. Therefore, the gradients of these increments are essential to search the yield space. However, the landscape of yield is not a simple one and mostly multi-modal. Another issue is differentiability. Engineering design problems are usually nonlinear and they sometimes exhibit discontinuous derivatives for …

Optimization Of The Odu Maglev System Ridership Performance, Eric Salvador M. De Leon

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of this research is to optimize the ODU People Mover project (Maglev vehicle) by providing a valid estimate of system "ridership" performance via modeling and simulation. The results considered both service parameters and cost of system operation. The system studied three stations on a line with no closed loop which was evidently unique, but the methods and approaches used for the problem can be applied to any transportation system or layout.

To achieve this objective -- design constraints and other relevant system inputs were identified that impacted the design parameters of the transportation system and permitted assessment of …

Modeling And Analysis Of Low Earth Orbit Satellite And Ground Station Data Exchange Topology, Ersin Kocoglu

Mechanical & Aerospace Engineering Theses & Dissertations

In order to utilize space effectively, the primary function of satellite control in orbit around the Earth must be accomplished. This controlling process includes two main segments, ground stations serving as the controller units and orbiting satellites as the units to be controlled. This thesis explores a topological data exchange model that contains one satellite and multiple ground stations. The model is implemented in digital computer software. This model has multiple purposes and can be used to simulate satellite passes over ground stations and can also be used to predict communication time and the amount of transferred data. The model …

Assessing The V2-F Turbulence Models For Circulation Control Applications, Travis M. Storm

Master's Theses

In recent years, airports have experienced increasing airport congestion, partially due to the hub-and-spoke model on which airline operations are based. Current airline operations utilize large airports, focusing traffic to a small number of airports. One way to relieve such congestion is to transition to a more accessible and efficient point-to-point operation, which utilizes a large web of smaller airports. This expansion to regional airports propagates the need for next-generation low-noise aircraft with short take-off and landing capabilities. NASA has attacked this problem with a high-lift, low-noise concept dubbed the Cruise Efficient Short Take-Off and Landing (CESTOL) aircraft. The goal …

An Experimental Study Of The Near Wake Field Behind A Propeller Aircraft, Hasan Ozgur Yavas

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents an experimental study of the wake behind a generic, high wing, half model of a propeller driven aircraft. Wake surveys are performed at a free stream velocity of 9m/s in the Old Dominion University Low-Speed Wind Tunnel. The objective of the study is understanding the general characteristics of development and interaction of tip vortices, flap vortices, and propeller vortices in the wake of a two propeller aircraft. The measurements in the wake were obtained by using hot-wire anemometry. Measurements were made both using single wire and X-wire probes mounted on a traverse mechanism on three planes behind …

Estimation And Management Of Observation Time For Low Earth Orbit Satellite, Serdar Cagirdar

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, time to observation for a generic low Earth orbit satellite after being tasked for reconnaissance of a particular surface target is investigated. A closed-form Keplerian propagation of the nominal orbit is used as the process for computing a solution to the time to observation for both scanning and staring sensors. Orbital maneuvers to reach the target sooner than the nominal trajectory are also considered. In this way time to observation is managed. Lambert's problem, which is used to determine an orbit of a satellite from two position vectors and the time of flight between them, is used …