Dynamic Gas-Surface Interaction Modeling For Satellite Aerodynamic Computations, 2011 University of Colorado at Boulder

#### Dynamic Gas-Surface Interaction Modeling For Satellite Aerodynamic Computations, Marcin Dominik Pilinksi

*Aerospace Engineering Sciences Graduate Theses & Dissertations*

Drag coefficients are a large source of uncertainty when predicting the aerodynamic forces on orbiting satellites. Accordingly, the focus of this research is to improve the fidelity of drag modeling by investigating the nature of gas-surface interactions in low earth orbit. The author has investigated to what extent oxygen adsorption can influence the parameters of drag coefficient models, most notably the energy accommodation coefficient. To accomplish this, several analysis techniques are applied. Fitted drag coefficients for 68 objects were provided by Air Force Space Command Drag Analysis Office and are analyzed using analytical and numerical aerodynamic models. Gas-surface parameters are ...

One-Dimensional Spacecraft Formation Flight Testbed For Terrestrial Charged Relative Motion Experiments, 2011 University of Colorado at Boulder

#### One-Dimensional Spacecraft Formation Flight Testbed For Terrestrial Charged Relative Motion Experiments, Carl Seubert

*Aerospace Engineering Sciences Graduate Theses & Dissertations*

Spacecraft operating in a desired formation offers an abundance of attractive mission capabilities. One proposed method of controlling a close formation of spacecraft is with Coulomb (electrostatic) forces. The Coulomb formation flight idea utilizes charge emission to drive the spacecraft to kilovolt-level potentials and generate adjustable, micronewton- to millinewton-level Coulomb forces for relative position control. In order to advance the prospects of the Coulomb formation flight concept, this dissertation presents the design and implementation of a unique one-dimensional testbed. The disturbances of the testbed are identified and reduced below 1 mN. This noise level offers a near-frictionless platform that is ...

Atmospheric Coupling Through Gravity Waves During Stratospheric Sudden Warmings: Gravity Wave Variations, Generation Mechanisms, And Impacts, 2011 University of Colorado at Boulder

#### Atmospheric Coupling Through Gravity Waves During Stratospheric Sudden Warmings: Gravity Wave Variations, Generation Mechanisms, And Impacts, Chihoko Yamashita

*Aerospace Engineering Sciences Graduate Theses & Dissertations*

Full understanding of gravity wave influences on the middle and upper atmosphere remains an unresolved research topic. The goals of this work are two-fold. First, gravity wave sources and propagation characteristics are explored using assimilated meteorological analyses from the European Centre for Medium-Range Weather Forecasting (ECMWF) during the 2009 stratospheric sudden warming (SSW). Second, gravity wave impacts on polar temperatures in the middle and upper atmosphere are examined by modulating the gravity wave parameterization scheme in the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM). Gravity waves that are resolved in ECMWFT799 are validated with satellite and lidar observations. ECMWF gravity wave potential ...

Modeling The Micro Behavior And Failure Of Collagen Based Fibrous Materials, 2011 University of Colorado at Boulder

#### Modeling The Micro Behavior And Failure Of Collagen Based Fibrous Materials, Spencer T. Hallowell

*Civil Engineering Graduate Theses & Dissertations*

The field of tissue engineering has expanded vastly over the last decade. Due to difficulties in testing tissues in vivo, numerical models must be produced to determine their mechanical behavior. Load bearing tissues in mammals are typically composed of collagenous fibrous networks connected by covalent cross links. To accurately model the behavior of these complicated tissues, a two dimensional Representative Volume Element has been formulated. The RVE utilizes truss elements, linear elastic springs and constraint forces to provide accurate behavior. The RVE behavior is calibrated to mimic experimental tensile testing of collagen gels by Xu et al. (International Journal of ...

An Analytical Theory For The Perturbative Effect Of Solar Radiation Pressure On Natural And Artificial Satellites, 2011 University of Colorado at Boulder

#### An Analytical Theory For The Perturbative Effect Of Solar Radiation Pressure On Natural And Artificial Satellites, Jay Warren Mcmahon

*Aerospace Engineering Sciences Graduate Theses & Dissertations*

Solar radiation pressure is the largest non-gravitational perturbation for most satellites in the solar system, and can therefore have a significant influence on their orbital dynamics. This work presents a new method for representing the solar radiation pressure force acting on a satellite, and applies this theory to natural and artificial satellites. The solar radiation pressure acceleration is modeled as a Fourier series which depends on the Sun's location in a body-fixed frame; a new set of Fourier coefficients are derived for every latitude of the Sun in this frame, and the series is expanded in terms of the ...

Influence Of Initial Mean Helicity On Homogeneous Turbulent Shear Flow, 2011 University of San Diego

#### Influence Of Initial Mean Helicity On Homogeneous Turbulent Shear Flow, Frank G. Jacobitz, Kai Schneider, Wouter J. T. Bos, Marie Farge

*School of Engineering: Faculty Scholarship*

Helicity statistics are studied in homogeneous turbulent shear flow. Initial mean helicity is imposed on an isotropic turbulence field using a decomposition of the flow into complex-valued helical waves. The initial decay of the turbulent kinetic energy is weakened in the presence of strong mean helicity, consistent with an analytic analysis of the spectral tensor of velocity correlations. While exponential growth of the mean turbulent kinetic energy is obtained, the mean helicity decays. Probability distribution functions (PDFs) of helicity are skewed and show that the imposed mean helicity prevails throughout the simulations. A wavelet-based scale-dependent analysis shows a trend to ...

Flight Control Design For A Tailless Aircraft Using Eigenstructure Assignment, 2011 CUNY Graduate Center

#### Flight Control Design For A Tailless Aircraft Using Eigenstructure Assignment, Clara Nieto-Wire, Kenneth Sobel

*Publications and Research*

We apply eigenstructure assignment to the design of a flight control system for a wind tunnel model of a tailless aircraft. The aircraft, known as the innovative control effectors (ICEs) aircraft, has unconventional control surfaces plus pitch and yaw thrust vectoring. We linearize the aircraft in straight and level flight at an altitude of 15,000 feet and Mach number 0.4. Then, we separately design flight control systems for the longitudinal and lateral dynamics. We use a control allocation scheme with weights so that the lateral pseudoinputs are yaw and roll moment, and the longitudinal pseudoinput is pitching moment ...

Techno-Economic Analysis And Engineering Design Consideration Of Algal Biofuel In Southern Nevada, 2011 University of Nevada, Las Vegas

#### Techno-Economic Analysis And Engineering Design Consideration Of Algal Biofuel In Southern Nevada, Jian Ma

*Mechanical Engineering Faculty Publications*

As the biological and chemical technologies in algae biofuels production, engineering design, siting and resources are playing some dominant role in successfully developing and scaling locally. The southwest region in U.S. has been identified by DoE and the USDA as the most suitable area for developing algal biofuel production due to several merits like the high level of solar radiation, large arid land not good for food production. Among this region, Southern Nevada has unique advantage to grow microalgae biomass, which is the large amount of CO2 emission from about 16 power plants in Clark County to support the ...

The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, 2011 Old Dominion University

#### The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar

*Mechanical & Aerospace Engineering Faculty Publications*

Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and ...

Flaw Detection In Multi-Layer, Multi-Material Composites By Resonance Imaging: Utilizing Air-Coupled Ultrasonics And Finite Element Modeling, 2011 Iowa State University

#### Flaw Detection In Multi-Layer, Multi-Material Composites By Resonance Imaging: Utilizing Air-Coupled Ultrasonics And Finite Element Modeling, Richard Livings

*Graduate Theses and Dissertations*

Ceramic tiles are the main ingredient of a multi–material, multi–layered composite being considered for the modernization of tank armors. The high stiffness, low attenuation, and precise dimensions of these uniform tiles make them remarkable resonators when driven to vibrate. Defects in the tile, during manufacture or after usage, are expected to change the resonance frequencies and resonance images of the tile. The comparison of the resonance frequencies and resonance images of a pristine tile/lay–up to a defective tile/lay–up will thus be a quantitative damage metric. By examining the vibrational behavior of these tiles and ...

3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, 2011 University of California, San Diego

#### 3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, Y. Bazilevs, Ming-Chen Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar

*Ming-Chen Hsu*

In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2 we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction ...

Quantifying Model Uncertainty Using Measurement Uncertainty Standards, 2011 Missouri University of Science and Technology

#### 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 ...

A Numerical Study Of Novel Drag Reduction Techniques For Blunt Bodies In Hypersonic Flows, 2011 Missouri University of Science and Technology

#### 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 ...

Shaker Table Vibration Testing Of A Microsatellite, 2011 Missouri University of Science and Technology

#### Shaker Table Vibration Testing Of A Microsatellite, Tonya Michelle Sanders

*Masters Theses*

"In the satellite development process, structural testing is a means to gain confidence in analytical models and ultimately support qualification of the spacecraft for flight. Vibration testing, in particular, is motivated by the safety considerations of crew or launch personnel, the survivability of delicate hardware and electronics, and the avoidance of large stresses that cause structural fatigue or failure. The subject of this thesis is concerned with the shaker table vibration testing of a microsatellite pair designed and built by students at the Missouri University of Science and Technology in Rolla, Missouri. A finite element model (FEM) used in structural ...

Uncertainty Quantification Integrated To Computational Fluid Dynamic Modeling Of Synthetic Jet Actuators, 2011 Missouri University of Science and Technology

#### 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 ...

Inherent And Model-Form Uncertainty Analysis For Cfd Simulation Of Synthetic Jet Actuators, 2011 Missouri University of Science and Technology

#### Inherent And Model-Form Uncertainty Analysis For Cfd Simulation Of Synthetic Jet Actuators, Daoru Frank Han

*Masters Theses*

"A mixed aleatory (inherent) and epistemic (model-form) uncertainty quantification (UQ) analysis method was applied to a computational fluid dynamics (CFD) modeling problem of synthetic jet actuators. A test case, (Case 3, flow over a hump model with synthetic jet actuator control) from the CFDVAL2004 workshop was selected to apply the Second-Order Probability framework implemented with a stochastic response surface obtained from Quadrature-Based Non-Intrusive Polynomial Chaos (NIPC). Three uncertainty sources were considered: (1) epistemic uncertainty in turbulence model, (2) aleatory uncertainty in free stream velocity and (3) aleatory uncertainty in actuation frequency. Uncertainties in both long-time averaged and phase averaged quantities ...

Continuous Low Thrust For Small Spacecraft Proximity Operations, 2011 Missouri University of Science and Technology

#### Continuous Low Thrust For Small Spacecraft Proximity Operations, James Harris Meub

*Masters Theses*

"Recently, both DoD and NASA have demonstrated increased interest in the development of close proximity operations for space systems. AFRL's Advanced Sciences and Technology Research Institute for Astrodynamics (ASTRIA) has defined several key research topics relevant to military priorities, with one area of critical importance being the inspection and observation of low Earth orbit resident space objects (RSOs). This study investigates the feasibility of using a low-thrust cold-gas propulsion system to effectively and accurately facilitate resident space object inspection. Specifically, this study focuses on the Missouri S&T Satellite mission (M-SAT) as a means to demonstrate autonomous RSO inspection ...

Magnetometer-Only Attitude Determination With Application To The M-Sat Mission, 2011 Missouri University of Science and Technology

#### Magnetometer-Only Attitude Determination With Application To The M-Sat Mission, Jason D. Searcy

*Masters Theses*

"The topic of this thesis focuses on attitude determination for small satellites. The method described uses only a magnetometer to resolve the three-axis attitude of the satellite. The primary challenge is that magnetometers only instantaneously resolve two axes of a satellite's attitude. Typically, magnetometers are used in conjunction with other sensors to resolve all three axes. However, by using a filter over an adequately long orbit arc, the magnetometer data can yield all the information necessary. The magnetic field data are filtered to obtain the magnetic field derivative vector, which are combined with the magnetic field vector to fully ...

Hall-Effect Thruster Surface Properties Investigation, 2011 Missouri University of Science and Technology

#### 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 ...

Computational Investigation Of Plasma Actuator As An Active Flow Control Strategy Of Laminar Separation Bubbles, 2011 Missouri University of Science and Technology

#### 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 ...