Aerospace Engineering Commons^™

Design, Analysis, And Optimization Of Composite Structures For Aerospace Applications, Tyler Jason Keil

Masters Theses

"This thesis contains three papers that focus on composites that pertain to a variety of structures commonly found in the aerospace industry. The first paper presents an investigation of the stowage and deployment strength of a thin carbon fiber-reinforced polymer shell capable of being rolled and stowed in a tight rolled configuration. The intent of this structure is for use as a segment of a larger deployable reflective aperture. This study involved finite element analysis of several laminates, coupon-level and full-scale prototype testing, which provided a much needed insight and benchmark of composite shells used in this manner.

The second …

On The Advantages Of E100 Over Gasoline In Down-Sized, Turbo-Charged, Direct-Injected, Variable Valve Actuated, And Stoichiometric S.I. Engines, Alberto A. Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Current flexi fuel gasoline and ethanol engines have efficiencies generally lower than dedicated gasoline engines. Considering ethanol has a few advantages with reference to gasoline, namely the higher-octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. the higher compression ratio and the higher boost permitted by ethanol allows …

Study Of Turbulence-Radiation Interaction In Hypersonic Turbulent Boundary Layers, L. (Lian) Duan, A. M. Feldick, M. P. Martín, M. F. Modest, D. A. Levin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In the paper, we conduct direct numerical simulations (DNS) to investigate the effect of turbulence-radiation interaction (TRI) in hypersonic turbulent boundary layers, representative of the Orion crew exploration vehicle (CEV) at peak heating condition during reentry. The radiative transfer equation (RTE) is solved using the tangent slab approximation. 1 The RTE solver is line-by-line (LBL) accurate, making use of a developed efficient spectral database 2 for spectral modeling. A multi-group full-spectrum correlated-k-distribution (FSCK) method 3 is used to reduce the number of RTE evaluations while preserving LBL accuracy. A nondimensional governing parameter to measure the significance of TRI is proposed, …

Assessment Of Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, L. (Lian) Duan, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Studies of the turbulence-chemistry interaction are performed in hypersonic turbulent boundary layers using direct numerical simulation flow fields under typical hypersonic conditions representative of blunt-body and slender body hypersonic vehicles, with super catalytic and noncatalytic wall conditions in pure air. Nondimensional governing parameters, the interaction Damköhler number and the interaction relative heat release, are proposed to measure the influence of turbulence-chemistry interaction on flow composition and temperature. Both a priori and posteriori studies are performed to assess the effect of turbulence-chemistry interaction on chemical production rates and mean and turbulent flow characteristics. It is found that the governing parameters provide …

Uncertainty Quantification Integrated To Computational Fluid Dynamic Modeling Of Synthetic Jet Actuators, Srikanth Adya

Masters Theses

"The Point Collocation Non-Intrusive Polynomial Chaos (NIPC) method was applied to a stochastic synthetic jet actuator problem to demonstrate the integration of computationally efficient uncertainty quantification to the high-fidelity CFD modeling of Synthetic Jet Actuators. The uncertainty quantification approach was first implemented in two stochastic model problem cases for the prediction of peak exit plane velocity using a Fluid Dynamic Based analytical model of the Synthetic Jet Actuator, which is computationally less expensive than CFD simulations. The NIPC results were compared with direct Monte Carlo sampling results. To demonstrate the efficient uncertainty quantification in CFD modeling of synthetic jet actuators, …

Study Of Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, Lian Duan, M. Pino Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Studies of the turbulence-chemistry interaction (TCI) are performed in hypersonic turbulent boundary layers using direct numerical simulation (DNS) flow fields under typical hypersonic conditions representative of blunt-body and slender-body hypersonic vehicles, with super catalytic and noncatalytic wall conditions in pure air. Nondimensional governing parameters, 'interaction' Damk̈ohler number and relative heat release, are proposed to measure the influence of TCI on flow composition and temperature. Both a priori and posteriori studies are performed to assess the effect of TCI on chemical production rates and mean and turbulence flow characteristics. In addition, an effective approach (called PDF-TS) to estimate the intensity of …

Use Of Bio-Ethanol And Bio-Diesel The Key Solution For A More Sustainable Road Transport, Alberto Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Life Cycle Analysis (LCA) of alternative transportation fuels clearly shows the advantages of reducing the use of nonrenewable fossil fuels vs. renewable biologic novel fuels to reduce the emissions of carbon dioxide. Being based on the natural recycle of carbon dioxide through the use of renewable energy sources, use of these renewable fuels does not imply depletion of natural resources and is therefore sustainable in the long term. Renewable fuels and advanced internal combustion engines and powertrains are the technologies that in addition to be the most likely to produce benefits in term of carbon balance and fossil fuel saving, …

Enhancement Technique For Aerial Images, Sertan Erkanli, Ahmet Gungor Pakfiliz, Jiang Li

Electrical & Computer Engineering Faculty Publications

Recently, we proposed an enhancement technique for uniformly and non-uniformly illuminated dark images that provides high color accuracy and better balance between the luminance and the contrast in images to improve the visual representations of digital images. In this paper we define an improved version of the proposed algorithm to enhance aerial images in order to reduce the gap between direct observation of a scene and its recorded image.

A Shock Tube Technique For Blast Wave Simulation And Studies Of Flow Structure Interactions In Shock Tube Blast Experiments, Nicholas N. Kleinschmit

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Improvised explosive devices (IED’s) are widely used against US and allied forces fighting in Iraq and Afghanistan. Exposure to IED blast may cause blast-induced traumatic brain injury (bTBI). The injury mechanisms are however not well understood. A critical need in bTBI-related research is the ability to replicate the loading conditions of IED blast waves in a laboratory environment. In this work, experimental studies have been carried out to explore the use of the shock tube technique for generating air shock waves that mimic the temporal and spatial characteristics of free-field blast waves and to investigate the blast wave-test sample interactions …

Robust Decentralized Formation Flight Control, Weihua Zhao, Tiauw Hiong Go

Aerospace, Physics, and Space Science Faculty Publications

Motivated by the idea of multiplexed model predictive control (MMPC), this paper introduces a new framework for unmanned aerial vehicles (UAVs) formation flight and coordination. Formulated using MMPC approach, the whole centralized formation flight system is considered as a linear periodic system with control inputs of each UAV subsystem as its periodic inputs. Divided into decentralized subsystems, the whole formation flight system is guaranteed stable if proper terminal cost and terminal constraints are added to each decentralized MPC formulation of the UAV subsystem. The decentralized robust MPC formulation for each UAV subsystem with bounded input disturbances and model uncertainties is …

Experimental Flow Visualization For Corrugated Airfoils At Low Reynolds Number Including Development Of A Pitch And Plunge Fixture, Jeremy Ryan Sparks

University of Kentucky Master's Theses

Micro Air Vehicles (MAV’s) have small size and extreme maneuverability which makes them ideal for surveillance. Propulsion mechanisms include propellers, rotors, and flapping airfoils. Flapping motions, along with biologically-inspired wing profiles, are of interest due to their use of natural physics. Corrugated airfoil structures appears to have poor aerodynamic performance at higher Reynolds numbers, but serve well at Re<10,000. Understanding flow structures around corrugated profiles and comparing them to a standard airfoil will aid in understanding how these corrugated profiles perform well and have been adopted by some of nature’s most acrobatic flyers. Motivation for this investigation is to compare static flow visualizations of corrugated profiles to a standard National Advisory Committee for Aeronautics (NACA) airfoil from low to high angles of attack and further observe flow structure development of a pitching and plunging flat plate at a Re<10,000 and a Strouhal number relevant to natural fliers. The static visualization was conducted at Re=1,000 with a NACA 0012 airfoil and two corrugated models. The Pitch and Plunge Fixture (PPF) developed was constructed by simplifying flapping wings as a two degree of freedom motion in plunge (translation) and pitch (rotation). Results obtained from the PPF were compared with a numerical simulation.

Perch Landing Maneuvers And Control For A Rotating-Wing Mav, Jonathan Louis Lubbers

University of Kentucky Master's Theses

This thesis addresses flight control of the perch landing maneuver for micro-aerial vehicles. A longitudinal flight model is constructed for a pigeon-sized aircraft. In addition to a standard elevator control surface, wing-rotation also considered as a non-standard actuator for increasing low-speed aerodynamic braking. Optimal state and control trajectories for the perch landing maneuver are computed using commercial software. A neighboring optimal control law is then developed and implemented in a set of flight simulations. Simulations are run with both a quasisteady and an unsteady aerodynamic model. The effectiveness of wing rotation and of the neighboring optimal control law is discussed, …

Ultra-Abrupt Tapered Fiber Mach-Zehnder Interferometer Sensors, B. Li, J. Lan, W. Sumei, L. Zhou, Hai Xiao, Hai-Lung Tsai

Electrical and Computer Engineering Faculty Research & Creative Works

A fiber inline Mach-Zehnder interferometer (MZI) consisting of ultra-abrupt fiber tapers was fabricated through a new fusion-splicing method. By fusion-splicing, the taper diameter-length ratio is around 1:1, which is much greater than those (1:10) made by stretching. The proposed fabrication method is very low cost, 1/20-1/50 of those of LPFG pair MZI sensors. The fabricated MZIs are applied to measure refractive index, temperature and rotation angle changes. The temperature sensitivity of the MZI at a length of 30 mm is 0.061 nm/°C from 30-350 °C. The proposed MZI is also used to measure rotation angles ranging from 0° to 0.55°; …

Exploring Increased Productivity Through Employee Engagement, Wayne K. Richards Jr.

Walden Dissertations and Doctoral Studies

Disengaged employees cost U.S. companies billions of dollars annually in lowered productivity, a cost which has been compounded by the difficult economic situations in the country. The potential for increasing productivity through increased employee engagement was examined in this study. Using personal engagement theory and the theory of planned behavior, the purpose of this phenomenological study was to explore how the experiences of salaried aerospace employees affected productivity and the financial performance of an organization. Interviews were conducted with a purposive sample of 20 aerospace employees whose responses were codified and analyzed to identify themes. The analysis indicated that (a) …

Uniform And Partially Uniform Redistribution Rules, Florentin Smarandache, Jean Dezert

Branch Mathematics and Statistics Faculty and Staff Publications

This paper introduces two new fusion rules for combining quantitative basic belief assignments. These rules although very simple have not been proposed in literature so far and could serve as useful alternatives because of their low computation cost with respect to the recent advanced Proportional Conflict Redistribution rules developed in the DSmT framework.

Evidence Supporting Measure Of Similarity For Reducing The Complexity In Information Fusion, Xinde Li, Jean Dezert, Florentin Smarandache, Xinhan Huang

Branch Mathematics and Statistics Faculty and Staff Publications

This paper proposes a new solution for reducing the number of sources of evidence to be combined in order to diminish the complexity of the fusion process required in some applications where the real-time constraint and strong computing resource limitation are of prime importance. The basic idea consists in selecting, among the whole set of sources of evidence, only the biggest subset of sources which are not too contradicting based on a criterion of Evidence Supporting Measure of Similarity (ESMS) in order to process solely the coherent information received. The ESMS criterion serves actually as a generic tool for outlier …

Hall-Effect Thruster Surface Properties Investigation, David George Zidar

Masters Theses

"Surface properties of Hall-effect thruster channel walls play an important role in the performance and lifetime of the device. Physical models of near-wall effects are beginning to be incorporated into thruster simulations, and these models must account for evolution of channel surface properties due to thruster operation. Results from this study show differences in boron nitride channel surface properties from beginning-of-life and after 100's of hours of operation. Two worn thruster channels of different boron nitride grades are compared with their corresponding pristine and shadow-shielded samples. Pristine HP grade boron nitride surface roughness is 9000±700 Å, while the worn sample …

A Numerical Study Of Novel Drag Reduction Techniques For Blunt Bodies In Hypersonic Flows, Christopher Marley

Masters Theses

"Numerical simulations of a full three-dimensional hemispherical body in hypersonic flow are conducted and innovative techniques involving forward injection of gas from the stagnation point of the sphere are investigated; techniques include annular (ring) and swirled injection both with and without upstream energy deposition. Objectives of the analysis are the assessment of 1) drag reductions achieved on the blunt body (including the detrimental drag effect caused by the forward-facing injection itself) and 2) stability characteristics of the jet. Studies are conducted at free-stream Mach numbers of 10 and 6.5 at standard atmospheric conditions corresponding to 30 km altitude. While centered …

Computational Investigation Of Plasma Actuator As An Active Flow Control Strategy Of Laminar Separation Bubbles, Justin Roger Aholt

Masters Theses

"A parametric computational study designed to examine the plausibility of an external body force generated by active means, such as a plasma actuator, as a means of controlling a Laminar Separation Bubble (LSB) over an airfoil at low Reynolds numbers was conducted. Computational Fluid Dynamics (CFD) was employed to characterize the effect that a body force, localized to a small region tangent to the airfoil surface, might have on an LSB. In this study, the effects of altering the strength and location of the "actuator" on the size and location of the LSB and on the aerodynamic performance of the …

Quantifying Model Uncertainty Using Measurement Uncertainty Standards, Harsheel Rajesh Shah

Masters Theses

"Model uncertainty quantification is mainly concerned with the problem of determining whether the observed data is consistent with the model prediction. In real world, there is always a disagreement between a simulation model prediction and the reality that the model intends to represent. Our increased dependence on computer models emphasizes on model uncertainty which is present due to uncertainties in model parameters, lack of appropriate knowledge, assumptions and simplification of processes. In addition, when models predict multi-variate data, the experimental observation and model predictions are highly correlated. Thus, quantifying the uncertainty has a basic requirement of comparison between observation and …