Engineering Commons^™

Flow Due To A Moving Pressure Distribution Over Free-Surface With Finite-Depth Bottom, Noriaki Okita

Masters Theses

Two-dimensional, steady-state and time-dependent analysis of wave making phenomenon due to a moving pressure distribution in sub-critical Froude number was performed. The domain is consisted of undisturbed free-surface at y=0, flat bottom at y=-h, and it is unbounded in horizontal direction. The pressure distribution was treated as an ideal model of an air-cushioned-vehicle (ACV). Ideal flow theory and linearized boundary conditions were used. Numerical integration algorithm was developed to evaluate the analytical solution. The surface elevation, bottom pressure profiles, and wave resistance were analyzed as functions of speed and depth.

The steady-state wave resistance calculated from the surface elevation profile …

Application Of Active Noise Control To Reduce Cabin Noise In Single Engine General Aviation Aircraft, Jeroen Hendrik Dolmans

Master's Theses - Daytona Beach

The application of active noise control to reduce cabin noise in single engine, general aviation aircraft is investigated through the use of the 'filtered x' least mean square algorithm and a simple acoustic feedforward method to generate a reference signal is tested. The system is designed to utilize one reference signal and up to two feedback signals and two audio speakers. The feedforward system consists of a microphone placed in close proximity to the front windshield and isolated from the cabin noise. Cabin noise and reference signals are recorded during flight in a Cessna 172 Skyhawk, a Piper Cherokee 140 …

Reverse Engineering Of Aircraft Wing Data Using A Partial Differential Equation Surface Model, Jacalyn M. Huband

Mathematics & Statistics Theses & Dissertations

Reverse engineering is a multi-step process used in industry to determine a production representation of an existing physical object. This representation is in the form of mathematical equations that are compatible with computer-aided design and computer-aided manufacturing (CAD/CAM) equipment. The four basic steps to the reverse engineering process are data acquisition, data separation, surface or curve fitting, and CAD/CAM production. The surface fitting step determines the design representation of the object, and thus is critical to the success or failure of the reverse engineering process. Although surface fitting methods described in the literature are used to model a variety of …

Aerospace And Foreign Policy, Ibpp Editor

International Bulletin of Political Psychology

The author discusses developing and implementing foreign policy towards the Peoples Republic of China regarding the market for aircraft and aerospace technology.

Determination Of Drag From Three-Dimensional Viscous And Inviscid Flowfield Computations, David L. Hunt, Russell M. Cummings, M. B. Giles

Aerospace Engineering

A momentum balance approach is used to extract the drag from flowfield computations for wings and wing/bodies in subsonic/transonic flight. The drag is decomposed into vorticity, entropy, and enthalpy components which can be related to the established engineering concepts of induced drag, wave and profile drag, and engine power and efficiency. This decomposition of the drag is useful in formulating techniques for accurately evaluating drag using computational fluid dynamics calculations or experimental data. A formulation for reducing the size of the region of the crossflow plane required for calculating the drag is developed using cut-off parameters for viscosity and entropy. …

Residual Strength After Fatigue Of A Cross-Ply Metal Matrix Composite At Elevated Temperature, Alvin N. Ruiz

Theses and Dissertations

The objective of this study was to investigate the residual strength of a cross-ply, SCS-6/Ti-15-3, metal matrix composite (MMC) at elevated temperature (427 °C) when exposed to fatigue loading. Several specimens were subjected to a strain-controlled, fully reversed loading (R=-1), at various strain levels. The specimens were fatigued up to a portion of their life expectancy and then loaded to failure. Stress and strain data obtained during the test provided useful information for the macro-mechanical behavior of the material. It was determined that the residual strength was directly related to the amount of damage present in the matrix, meanwhile, the …

Control Of Nonlinear Systems Via State Feedback State-Dependent Riccati Equation Techniques, Kelly D. Hammett

Theses and Dissertations

Nonlinear regulation and nonlinear H-infinity control via state-dependent Riccati equation (SDRE) techniques are considered. Relationships between SDREs and Hamilton-Jacobi/Bellman inequalities/equations are examined, and a necessary condition for existence of solutions involving nonlinear stabilizability is derived. A single additional necessary criterion is given for the SDRE methods to yield the optimal control or guaranteed induced L2 gain properties. Pointwise stabilizability and detectability of factorizations prove necessary and sufficient, respectively, for well-posedness of standard numerical implementations of suboptimal SDRE regulators, but neither proves necessary if analytical solutions are allowed. For scalar analytic systems or those with full rank constant control input matrices, …

Stepped Tip Gap Effects On A Transonic Axial-Flow Compressor Rotor, Donald W. Thompson

Theses and Dissertations

The effects of stepped tip gaps and clearance levels on the performance, flowfield, and stall characteristics of a transonic axial-flow compressor rotor were experimentally and numerically determined. A theory and mechanism for relocation of blockage in the rotor tip region was developed. A two-stage compressor with no inlet guide vanes was tested in the Wright Laboratories Compressor Research Facility located at Wright-Patterson Air Force Base, Ohio. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were …

Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong

Theses and Dissertations

This study investigated the feasibility of a SAIC proposal to sample Near Earth Objects (NEOs) from an orbiting spacecraft using a tethered landing device. The parameters for suitable targets were derived from an analysis of a proposed point design as applied to current knowledge of NEOs. Tether strength and lifetime for the point design were also assessed. First order modeling of tether dynamics showed that deployment and attachment to a NEO are feasible. The dynamics of retrieving a sample via a crawler unit which crawls up the tether requires further exploration.

An Investigation Of Unsteady Vortex Flow Over A Maneuvering Delta Wing, Harry James Kowal

Doctoral Dissertations

An investigation of the vortex breakdown phenomenon using flow visualization qualitatively and quantitatively was conducted with a 70° delta wind under conditions of steady and unsteady pitch, roll and combinations of pitch and roll. Testing was carried out in the water tunnel located in the Mechanical Engineering Department of the Royal Military College of Canada, Kingston, Ontario.

Steady state roll experiments with the delta wing pitched at 30° showed that the behavior of vortex breakdown as a function of roll angle could be considered linear over the front half of the delta wing; however, the behavior beyond a certain critical …

Testing Of Solid Rocket Propellants With An Ultrasonic Transducer, Bryan Rasmussen

Honors Capstone Projects and Theses

No abstract provided.

Freezing Point Mobile Munitions Assessment Sytem: Thermal Chamber Redesign, Sara Gifford, Preston Harris

Undergraduate Honors Capstone Projects

The Army is actively investigating non-intrusive methods to identify six chemical weapons agents. The chemical munitions in question are often found scattered across military bases and other facilities. These non-stockpile munitions are specifically targeted for identification using the mobile munitions assessment system. This program is being administered by the Idaho National Engineering Laboratory.

The Pratt & Whitney 4060: Power For The Future, Gregory Sumner

Honors Theses

The Pratt & Whitney 4000 engine platform is considered the most economical turbofan engine in its class. It is advertised as providing the most efficient service and the most reliability for air carriers. United Airlines utilizes the company's engines. The paper begins with basic turbine engine theory and moves on to engine classifications, where the Pratt & Whitney 4060 is introduced. The systems are covered in detail. Maintenance areas of service and inspections are described to show how personnel may interact with the computers. Finally, a description of activities during the author's internship describe the interesting facets of a semester …

Cooperative Power-Limited Optimal Rendezvous Between Many Spacecraft, Virginie Guerre

Master's Theses - Daytona Beach

The minimum fuel rendezvous problem between several power-limited low-thrust spacecraft neighboring either a circular or an elliptic orbit is investigated. Both cooperative and non cooperative maneuvers are studied. The maximum principle of Pontryagin is applied to the optimal control rendezvous problem of several spacecraft. The gravitational field models investigated are the Clohessy-Wiltshire field and the inverse-square gravity field. Numerical solutions using a shooting method and the finite difference method are used in order to determine the trajectories of the spacecraft. Unlike previous investigations, this work is not restricted to a rendezvous of two spacecraft around a circular orbit, but a …

Development And Initial Evaluation Of An Acoustic Apparatus Used For Testing Of Farfield Noise Emitted By A Propeller In A Short Duct, R. Duane Oleson

Master's Theses - Daytona Beach

The purpose of this thesis was to design, construct and evaluate an apparatus which was used for testing of acoustic emissions by a propeller in a short duct. An apparatus was designed based on a combination of acoustic principles and a desire to be able apply the knowledge gained to a practical application such as an ultralight aircraft in an effort to reduce the overall noise levels emitted. The apparatus consisted of a 35 horsepower ultralight engine, a four bladed ultralight propeller, and a duct constructed of a foam core covered with fiberglass. Initial evaluations compared noise levels from the …

The Design And Experimental Optimization Of A Wingtip Vortex Turbine For General Aviation Use, Andrew Roberts

Master's Theses - Daytona Beach

A wingtip vortex turbine (WVT) is an induced drag reduction device that straightens the vortex flow (reducing induced drag and wake turbulence) and also produces a thrust force component. The WVT also has the advantage of extracting the rotational energy of the vortex to turn a generator, which could be used to power onboard applications during normal or emergency flight operations. A 1/4-scale model of a thrust-producing WVT has been designed and tested in a wind tunnel for optimal drag reduction and power generation for general aviation aircraft — specifically, a Piper Cherokee — in both a stationary and a …

Hybrid Rocket Powered Upper Stage Design Report, Imran Mukhtar

Honors Capstone Projects and Theses

No abstract provided.

Flightlines, Vol. 5, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Three-Dimensional Aerodynamic Design Optimization Using Discrete Sensitivity Analysis And Parallel Computing, Amidu Olawale Oloso

Mechanical & Aerospace Engineering Theses & Dissertations

A hybrid automatic differentiation/incremental iterative method was implemented in the general purpose advanced computational fluid dynamics code (CFL3D Version 4.1) to yield a new code (CFL3D.ADII) that is capable of computing consistently discrete first order sensitivity derivatives for complex geometries. With the exception of unsteady problems, the new code retains all the useful features and capabilities of the original CFL3D flow analysis code. The superiority of the new code over a carefully applied method of finite-differences is demonstrated.

A coarse grain, scalable, distributed-memory, parallel version of CFL3D.ADII was developed based on "derivative stripmining". In this data-parallel approach, an identical copy …

Aerodynamic Gradient-Based Optimization Using Computational Fluid Dynamics And Discrete Sensitivities For Practical Problems, Mohagna Jayendrarai Pandya

Mechanical & Aerospace Engineering Theses & Dissertations

A gradient-based shape optimization methodology based on quasi-analytical sensitivities has been developed for practical three-dimensional aerodynamic applications. The flow analysis has been rendered by a fully implicit, finite-volume formulation of the Euler and Thin Layer Navier-Stokes (TLNS) equations. The flow equations and aerodynamic sensitivity equation have been solved using an alternating-direction-implicit (ADI) algorithm for memory efficiency. A wing geometry model based on space-surface and planform parameterization has been utilized. The present methodology and its components have been tested via several comparisons.

Initially, the inviscid flow analysis for a wing has been compared with those obtained using an unfactored, Preconditioned Conjugate …

Input Design For Systems Under Identification Using Indirect And Direct Methods, Marco P. Schoen

Mechanical & Aerospace Engineering Theses & Dissertations

The motivation for system identification can be manifold. In this work, the provocation to identify unknown system characteristics is derived from the control engineering point of view. That is, one intends to design a control strategy based on the identified system properties. The used system identification methods are the Open-Loop Kalman filter System Identification method (OKID) and the Closed-Loop System Identification method (CLID). It is shown that the quantitative largest error of the system identification is given by its model representation, that is the attempt to describe a system with model parameters which poses a linear relationship with the input/output …

Advances In Time-Domain Electromagnetic Simulation Capabilities Through The Use Of Overset Grids And Massively Parallel Computing, Douglas C. Blake

Theses and Dissertations

A new methodology is presented for conducting numerical simulations of electromagnetic scattering and wave propagation phenomena. Technologies from several scientific disciplines, including computational fluid dynamics, computational electromagnetics, and parallel computing, are uniquely combined to form a simulation capability that is both versatile and practical. In the process of creating this capability, work is accomplished to conduct the first study designed to quantify the effects of domain decomposition on the performance of a class of explicit hyperbolic partial differential equations solvers; to develop a new method of partitioning computational domains comprised of overset grids; and to provide the first detailed assessment …

Modern Flight Control Design, Implementation, And Flight Test, Phillip T. Edwards

Theses and Dissertations

This thesis addresses the application issues raised implementing flight control designs derived from optimal control theory and the challenges in obtaining acceptable handling qualities when using these techniques. Using the USAF TPS FCS project as the controller architecture, four controllers were designed using classical methods, and H2, H3, and mixed H2/H optimal control theory. These designs were implemented in the Calspan VSS II Learjet, simulating unstable aircraft longitudinal dynamics and a limited handling qualities flight test evaluation was performed. The design phase found the optimal control techniques, as applied, difficult to design to handling qualities specifications. The H2, H3 and …

Nested Fork-Join Queuing Networks And Their Application To Mobility Airfield Operations Analysis, Craig J. Willits

Theses and Dissertations

A single-chain nested fork-join queuing network (FJQN) model of mobility airfield ground processing is proposed. In order to analyze the queuing network model, advances on two fronts are made. First, a general technique for decomposing nested FJQNs with probabilistic forks is proposed, which consists of incorporating feedback loops into the embedded Markov chain of the synchronization station, then using Marie's Method to decompose the network. Numerical studies show this strategy to be effective, with less than two percent relative error in the approximate performance measures in most realistic cases. The second contribution is the identification of a quick, efficient method …

The Effects Of Elevator Rate Limiting And Stick Dynamics On Longitudinal Pilot-Induced Oscillations, Patrick J. Peters

Theses and Dissertations

This report presents the results of an investigation into the effects of elevator rate limiting and stick dynamics on longitudinal pilot-induced oscillations (PIO). A simulation study was conducted to prepare for the flight test, but also to gain insight into the effects of rate limiting and stick dynamics. Due to the non-numerical nature of the simulation results, a flexible three-phase flight test plan was developed, first varying the rate limits, then varying the stick dynamics, and finally flying a matrix determined in the first two phases. There were three major conclusions. First, the offset landing task flown was insufficient to …

An Object Oriented Simulation Of The C-17 Wingtip Vortices In The Airdrop Environment, Hans J. Petry

Theses and Dissertations

This thesis effort focuses on the development of an object-oriented simulation of C-17 personnel airdrop operations and provides a tool for risk assessment of jumper and wingtip vortex interaction. Using the initial modeling efforts of the Wright Laboratory, this model expands those efforts to include random aircraft, wind and jumper movement within the simulation using MODSIM III as its language. Once the model was built, verified, and calibrated, it helped perform a preliminary analysis of jumper risk with varying element spacing and no crosswind. The results of the simulation provided 15 data points with which linear and logistic regression provided …

Numerical And Experimental Investigation Of The Flowfield Near A Wrap-Around Fin, Carl P. Tilmann

Theses and Dissertations

A wall-mounted semi-cylindrical model fitted with a single wrap-around fin (WAF) has been investigated both numerically and experimentally, with the objective of characterizing the mean and turbulent flowfield in the vicinity of the fin. Numerical and experimental results are used to determine the nature of the flowfield and quantify the effects of fin curvature on the character of the flow near WAFs. This research has been motivated by the need to identify possible sources of a rolling moment reversal observed at high speeds in sub-scale flight tests. Detailed mean flow and turbulence measurements were obtained in the AFIT Mach 3 …

An Investigation Of The Hydrodynamic Effects Of Enteromorpha Clathrata Fouling On Hydrofoils, Brian J. Collino

Master's Theses - Daytona Beach

The purpose of this investigation was to determine the effects of biological fouling on hydrofoils. NACA 4412 and 4415 hydrofoil models with 6 inch chord and 8 inch span were used in this study. A water tunnel facility was designed and constructed to perform the tests, and the results were verified using computational fluid dynamic modeling. The CFD software package Fluent was used to create a two dimensional model of the water tunnel test section and hydrofoil. The model was meshed using a Laplacian grid smoothing technique that forced the structured grid lines to follow the same approximate contour as …

Cosmic Calling

Syracuse University Magazine

No abstract provided.

The Nuts & Bolts Of Cooperative Learning In Engineering, Nikos J. Mourtos

Nikos J. Mourtos

A great number of engineering students work alone most of the time. This is in sharp contrast with industry where most of the work is performed in teams. The ability to work in a team effectively is not acquired automatically. It takes interpersonal and social skills which need to be developed and practiced. In addition, research shows that the student-student interaction, often neglected in traditional ways of teaching, is a most effective way of learning. Thus, it is imperative that we encourage our students to work with each other in their efforts to achieve their educational goals. In this paper …