Engineering Commons^™

Computation Of Hypersonic Flows With Lateral Jets Using K-Ω Turbulence Model, Spatika Dasharati Iyengar

Doctoral Dissertations and Master's Theses

Thermal Protection systems (TPS) are used as shields in space vehicles which encounter high heat and temperatures at the reentry altitudes. Among them, the cooling techniques and the ablative coatings are most popular. However, they have their own weight limitations. In the recent decade, another classification of TPS called the Non-Ablative Thermal Protection systems (NaTPS) have gained significance. The spike-lateral jet method is an NaTPS concept proposed for drag and heat flux reduction in hypersonic nose cones. Numerical simulations are conducted to analyze the effectiveness of spike-lateral jet concept at re-entry altitudes. The spike attached to the hemispherical nose has …

Experimental And Computational Investigation Of Ribbed Channels For Gas Turbine Thermal Management, Yash T. Mehta

Doctoral Dissertations and Master's Theses

This study focuses on the computational benchmarking as well as validation against experimental results of a rib roughed surface in an internal channel of a stationary turbine blade. STAR-CCM+ was utilized to replace a model from a published article, and to analyze the CFD conjugate heat transfer by determining the turbulence model that best matched the published experimental values. Using those computational conditions and CFD results, an in house experimental rig was validated by comparing convective heat transfer coefficients and pressure profiles. This cooling method, when compared to a smooth channel, enhances turbulent mixing my separating and reattaching the boundary …

Direct Adaptive Control For Stability And Command Augmentation System Of An Air-Breathing Hypersonic Vehicle, Ron Aditya

Doctoral Dissertations and Master's Theses

In this paper we explore a Direct Adaptive Control scheme for stabilizing a non-linear, physics based model of the longitudinal dynamics for an air breathing hypersonic vehicle. The model, derived from first principles, captures the complex interactions between the propulsion system, aerodynamics, and structural dynamics. The linearized aircraft dynamics show unstable and non-minimum phase behavior. It also shows a strong short period coupling with the fuselage-bending mode. The value added by direct adaptive control and the theoretical requirements for stable convergent operation is displayed. One of the main benefits of the Directive Adaptive Control is that it can be implemented …

Lagrangian Points And Jacobi Constants For A Class Of Asteroids, Tasneem Rashid

Doctoral Dissertations and Master's Theses

Asteroid Gravitational Potentials are difficult to model owing to their irregularity in shape. This thesis focuses on two approaches to model asteroid gravity fields, namely, multiple-body and spherical harmonics modeling. Computation of gravity potential serves as a first step to determine equilibrium points called Lagrangian points for a spacecraft orbiting as an asteroid. Further, Jacobi analysis is carried out to determine zero-velocity regions, i.e., inaccessible regions corresponding to the unstable Lagrangian points. Multiple sphere modeling was studied through analysis of so called Asteroid Restricted Three and Four Body Problems, providing insight into the method of modeling an asteroid as a …

Aerodynamic Trade Study Of Compound Helicopter Concepts, Julian Roche

Doctoral Dissertations and Master's Theses

The relative performance attributes of compound helicopter concepts have been examined, including their potential for meeting the requirements of several challenging mission profiles. For each concept, which included lift and/or propulsive compounding, a suite of aerodynamic performance models was developed using energy methods. In the case of a lift-compounded concept, an aerodynamic model representing the force interaction effects of the main rotor wake with the wing was also developed. Models of a conventional helicopter and of a tiltrotor were implemented as well, and the results used as a datum for comparison. In each case, the predictive capabilities of the model …

An Investigation Of Cooling Configurations In Gas Turbine Engines Using Jet Impingement, Bhushan Upalkar

Doctoral Dissertations and Master's Theses

A numerical investigation for predicting the heat transfer effects of turbulence was conducted by making a scaled-up model of a section in a jet impingement channel. Different turbulence models were run and the results were compared to experimental data. Experimental comparisons were made for impingement channels between a baseline case, which is a rectangular array of jets of 20 rows and 3 jets per row, and different hole spacing configurations. The heat transfer was measured using Temperature Sensitive Paint. The turbulence model v²-f gave the most accurate prediction with an error of about 17% with the EB k-E, with an …

Low-Velocity Impact Analysis Of Composite Repair Patches Of Different Shapes, Sarvesh Baliga

Doctoral Dissertations and Master's Theses

The area under crack for various structures can be effectively repaired by the use of composite materials. Low velocity impact can cause barely visible damage to the interior structure of laminated composite. These impacts can cause delamination in composite materials. In this study, a Finite Element Analysis was conducted using Abaqus/Explicit and the results of the analysis were compared to the experimental data from literature. E-glass/epoxy composite laminate was subjected to a low velocity impact test. To study the effect of patch repair, a composite patch was applied on a cracked laminate and a low velocity impact was then conducted …

Design, Fabrication, And Testing Of A Proprioceptive Electroadhesion Pad For Space Applications, Walter Saravia

Doctoral Dissertations and Master's Theses

The purpose of this study is to design, analyze, and fabricate an electroadhesion mechanism with the goal of providing controlled electrostatic adhesion to objects with little known surface finish, of varying curvature, and different materials. The main purpose of the mechanism is that of ensuring a soft docking, controlled in closed loop, for attachment to large pieces of orbital debris. Other envisaged purposes for the mechanism are sample collection and manipulation in free-fall and in-situ analysis of cohesive forces in regolith at small bodies, such as asteroids or comets. Electrostatic finite element analysis was performed on various electroadhesion pad designs …

Numerical Study Of Synthetic-Jet Actuation Effect On Airfoil Trailing Edge Noise, Marco Sansone

Doctoral Dissertations and Master's Theses

The current study conducts numerical simulations to assess the possibility of employing Synthetic Jet Actuators (SJAs) as active noise control devices for reduction of airfoil acoustic radiation. High-accuracy numerical efforts employ a sixth-order accurate Navier-Strokes solver implementing a low-pass filtering of poorly resolved high-frequency solution content to retain numerical accuracy and stability over the range of transitional flow regimes. In the adopted numerical procedure, the actuator is modeled without its resonator cavity through imposing a simple fluctuating-velocity boundary condition at the bottom orifice of the actuator. The orifice cavity with the properly defined boundary condition is embedded into the airfoil …

The Three-Dimensional Turbulent Boundary Layer On A Rotating Disk, Daniel Digre

Doctoral Dissertations and Master's Theses

Three-dimensional turbulent boundary layers (3DTBL) are seen quite commonly in nature as well as in the engineering applications. Despite this, very few high Reynolds number studies have been carried out on these boundary layers, particularly focusing on eddy structure, eddy scales and their interactions. The current study focused on developing, characterizing and evaluating an experimental framework to study high Reynolds number #3DTBL on a rotating disk with the long-term goal of carrying out high-fidelity measurements. The rotating disk flow is characterized by weak centrifugal pumping which sets up the cross flow that leads to turbulence. The tangential and radial velocities …

Similarity Analysis Of A Swirling Counter-Flow, Jitesh Rane

Doctoral Dissertations and Master's Theses

Swirling counter-flows are used in numerous engineering applications, like combustion, heat exchangers, cyclonic separation and mixing, etc. These swirling counter-flows produce complex flow fields. It is important to study these types of flows in order to use them properly in many applications.

The present work provides insight into the flowfield inside a swirling counter-flow when the fluid is injected tangentially in a cylindrical container. A semi-analytical solution is developed by starting with the full Navier-Stokes equation and using a similarity analysis. A decaying swirl along the axis of the cylinder is assumed, which reduces the Navier-Stokes equations to first order …

Design Of Synthetic Jet Actuator For Flight Control Of Small Uav, Priyanka Pagadala

Doctoral Dissertations and Master's Theses

The main idea of this project is to develop a prototype SJA - Synthetic Jet Actuator to embed into a small UAV with modified Glauert wing cross-section for Active Flow Control. Apart from lift enhancement, drag reduction, or separation control, etc; LCO suppression might be possible by modifying the boundary layer through the use of these actuators. For initial investigation, a wing section with span of 12.4 cm and chord of 14 cm was fabricated and tests were conducted in the subsonic wind tunnel at the free stream velocities of 5 and 10 m / s. From these experiments, lift …

Sensor Fusion And Obstacle Avoidance For An Unmanned Ground Vehicle, Gurasis Singh

Doctoral Dissertations and Master's Theses

In recent years, the capabilities and potential value of unmanned autonomous systems (UAS) to perform an extensive variety of missions have significantly increased. It is well comprehended that there are various challenges associated with the realization of autonomous operations in complex urban environments. These difficulties include the requirement for precision guidance and control in conceivably GPS-denied conditions as well as the need to sense and avoid stationary and moving obstructions within the scene. The small size of some of these vehicles restricts the size, weight and power consumption of the sensor payload and onboard computational processing that can accommodated by …

Supersonic Retro-Propulsion Computational Fluid Dynamics Analysis Applied To Future Mars Mission, Margarita Nataly Brandt

Doctoral Dissertations and Master's Theses

Supersonic Retro-Propulsion is one of the most promising emerging technologies being considered by NASA for use in future Mars missions. This new form of Entry Descent Landing has the potential to help increase the allowable payload mass currently constraining many science instruments and operations. Computational Fluid Dynamics was used to show the feasibility of supersonic retro - propulsion in Mars atmospheric conditions. The results presented show the SRP will be able to perform satisfactory using the same conditions that the Curiosity Rover was exposed to during its landing sequence. The plume expansion was analyzed for various cases, moving from free …

Aerodynamic And Structural Design Of A Winglet For Enhanced Performance Of A Business Jet, Nicolas El Haddad

Doctoral Dissertations and Master's Theses

The preliminary design of a winglet to improve the range and fuel burn of the Falcon 10 business jet is presented. Twelve candidate geometries were studied varying the cant angle and the span. The configuration offering the best compromise between induced drag reduction, profile drag increase and weight increase due to the winglet structure and necessary wing structural reinforcement was selected. More refined analysis was performed for that winglet with Reynolds averaged Navier-Stokes computational fluid dynamics and finite element analysis. Range and fuel burn were finally calculated for a typical mission using these refined results. The selected winglet, with a …

Modeling And Simulation Of Radiation From Electronic Transitions In Hypersonic Atmospheric Reentry Flow, Curtis Scholz

Doctoral Dissertations and Master's Theses

A capability for higher accuracy heat transfer modeling in CFD for hypersonic re-entry flows, via inclusion of thermal radiation, is sought. With temperatures reaching tens of thousands of degrees, radiation is known to be significant to chemical reaction rates and thermal boundary layer development, hence surface heat transfer and thermal ablation both to the heat shield and the backshell region of re-entry vehicles. Two current NASA solicitations seek such an improved capability relative to the Mars and Earth entry problems, as uncertainty typically leads to overdesign and excess weight. The present research develops a first physics-based “building block,” which computes …

Surface Structure And Its Effect On Reducing Drag, Ragini Ramachandran

Doctoral Dissertations and Master's Theses

A miniature subsonic open return wind tunnel was designed and fabricated to measure drag on small test models at low Reynolds numbers. The wind tunnel featured a sensitive strain gauge type load cell. The average drag coefficient of sphere and cube test models were used to validate the miniature wind tunnel, and the values obtained were consistent with published results over the range of Reynolds numbers tested. These initial results gave confidence that the tunnel could be used to study the effects of surface finish on the drag of various models. Several fabrics with differing ribbed surface structures, including a …

Attitude Determination & Control System Design And Implementation For A 6u Cubesat Proximity Operations Mission, Francisco J. Franquiz

Doctoral Dissertations and Master's Theses

The purpose of this work is to discuss the attitude determination and control system (ADCS) design process and implementation for a 12 kg, 6U (36.6 cm x 23.9 cm x 27.97 cm) CubeSat class nano-satellite. The design is based on the requirements and capabilities of the Application for Resident Space Object Proximity Analysis and IMAging (ARAPAIMA) proximity operations mission. The satellite is equipped with a cold gas propulsion system capable of exerting 2.5 mN m torques in both directions about each body axis. The attitude sensors include an angular rate gyro and star tracker (STR), supplemented by the payload optical …

Phased Array Beamsteering In Composite Laminates For Guided Wave Structural Health Monitoring, Peter Osterc

Doctoral Dissertations and Master's Theses

In this study a guided wave phased array beamsteering approach is applied to composite laminates. Current beamsteering algorithms derived for isotropic materials assume omnidirectional wave propagation. Due to inherent anisotropy in composites, guided wave propagation varies with direction and wavefronts no longer have perfect circular shapes.

By examining slowness, velocity and wave curves, as well as amplitude variation with direction for a given composite laminate, the wavefront from a single source can be described as a function of the angle of propagation and distance from origin. Using this approach, a more general delay and sum beamforming algorithm for composite laminates …

Determination Of A Simplified High-Order Vortex Equation For Radial Equilibrium With Cfd Verification, Travis K. Matsumoto

Doctoral Dissertations and Master's Theses

The goal of this thesis is to determine a flow model that provides a better blade design over current design techniques utilizing a hybrid vortex model. This hybrid vortex model combines the well-established simple radial equilibrium vortex models into a higher order equation that will establish the basis for a more flow-accurate model. In this paper, we will discuss the basis and derivation of these vortex models, the shortcomings of current techniques, and verification of the new vortex model with empirical data via Computational Fluid Dynamic (CFD). The simple radial equilibrium equation set has been known to the scientific community …

Scalloped Leading Edge Vaned Diffuser Analysis For A Compact High Pressure Ratio Centrifugal Compressor, Vinod Poonamchand Gehlot

Doctoral Dissertations and Master's Theses

Microturbines and small gas turbines are often an attractive option for turbo-hybrid application research in aviation due to their simple design and high power to weight ratio. However, the low operating pressure ratios of microturbines leads to low thermal efficiency, which results in very high fuel consumption. Higher operating pressure ratios in microturbines could vastly improve their current fuel efficiency. This thesis focuses on developing a compact, single stage 8:1 pressure ratio centrifugal compressor stage designed to meet the high-pressure ratio requirements of microturbines and small gas turbine engines in turbo hybrid-electric propulsion applications. The first stage vaned diffuser was …

Numerical Investigation Of Tonal Noise On A Transitional Airfoil Under Varying Conditions, Warren W. Hiner

Doctoral Dissertations and Master's Theses

The generation of discrete acoustic tones is a problem of interest in transitional airfoils. Such tones exist for moderate Re below 2,000,000 and for low to moderate angles of attack. The purpose of this study is to use linear stability theory to study the growth of instabilities on the pressure and suction surfaces of airfoils for varying Re between 144,000 and 468,000 and angles of attack between 0˚ and 12˚. High accuracy 2D simulations based on an Implicit Large Eddy Simulation (ILES) code are conducted for a NACA0012 airfoil for varied conditions, and linear stability analysis is performed to predict …

The Design For Manufacturing And Assembly Analysis And Redesign Of An Aircraft Refueling Door Hinge Utilizing Additive Manufacturing, Kurt A. Schwarz

Doctoral Dissertations and Master's Theses

In this thesis, an aircraft door hinge assembly provided by Gulfstream Aerospace was analyzed following an established process called DFMA. The hinge was then redesigned to be additively manufactured, which is uncommon currently in industry for load bearing components. It was shown that the Design for Manufacturing (DFM) guidelines were inadequate when applied to the new technology of additive manufacturing (AM). This was primarily due to AM's unique and unprecedented manufacturing capabilities.

A conservative redesign approach was followed due to a limitation in current AM material properties and time available for analysis. Despite this, a significant improvement in weight reduction …

Benchmarking Of Computational Models Against Experimental Data For Adiabatic Film-Cooling Effectiveness For Large Spacing Compound Angle Full Coverage Film Cooling Arrays, Simon R. Martinez

Doctoral Dissertations and Master's Theses

This study aims to benchmark experimental data that tested the effects of blowing ratio, surface angle, and hole spacing for two full coverage geometries composed of cylindrical staggered holes at a compound angle of 45 degrees. These holes varied parametrically the inclination angle to be 30 and 45 degrees, while maintaining a lateral and axial spacing of 14.5 hole diameters. Within this study, the local film cooling effectiveness was obtained from 30 rows for the 14.5 diameter spacing. Utilizing a velocity profile at the crossflow inlet produced significant differences in the results produced when compared to a uniform freestream velocity …

Investigation Of Pulse Detonation Engines: The Effect Of Variable Blockage Ratio On The Deflagration To Detonation Transition, Christopher Tate

Doctoral Dissertations and Master's Theses

Detonation and constant volume combustion is well known to be thermodynamically more efficient than the typically utilized constant pressure. There have been numerous approaches of achieving detonation through deflagration-to-detonation transition most of which use evenly spaced obstacles with a specified constant blockage ratio to generate turbulence and pressure fluctuations. There have been few efforts to study effects of varying blockage ratio as a function of axial distance. This research analyzes the effect of variable blockage ratio on deflagration-to-detonation transition in ethylene-air mixtures. The experiments show that with certain blockage ratio functions detonation is more repeatable and produces a smaller variation …

Analysis Of A Hybrid Rocket Burn Using Generalized Compressible Flow, Naveen Sri Uddanti

Doctoral Dissertations and Master's Theses

The analysis of square ports in a hybrid rocket is simple when compared to other complicated port geometries such as a wagon wheel configuration. In the present work, fuel grains with several ports in a hybrid rocket engine are analyzed by transforming the ports into equivalent square ports. As an example, the internal ballistics of a hybrid rocket with circular ports is analyzed by transforming it to an equivalent solid grain with square ports having the same amount of solid fuel and burn time. The results obtained are similar to that of circular port but with a slight decrease in …

Comparing Different Methods For Estimating Total Open Heliospheric Magnetic Flux, Samantha J. Wallace

Doctoral Dissertations and Master's Theses

There are extended periods over the solar cycle where significant discrepancies occur between the observed open magnetic flux (i.e., those based on spacecraft observations) and that determined from coronal models. One explanation for the source of these discrepancies is the magnetic fields in CMEs, which have yet to magnetically disconnect from the Sun. These “closed” flux sources can be included in open flux estimates, because open and closed magnetic field lines are not easily distinguished in spacecraft data. Another possibility is that a portion of the open flux measured by in situ spacecraft originates from the time-dependent evolution of solar …

Aircraft De-Icing System Using Thermal Conductive Fibers, Min Soon Park

Doctoral Dissertations and Master's Theses

The accumulation of ice on the leading edges of aircraft wing poses complications for flight control as drag is increased with a tendency for higher relative turbulence over the wing. Pre-emptive and reactive ice removal techniques have been employed in the past by electromechanical, thermal, chemical and pneumatic methods. In this thesis, a carbon fiber fabric is utilized as a heating de-icer for composites aircraft wing surface structures. Two prototypes are constructed, tested to generate temperature profiles, and an appropriate heating voltage is selected for effective de-icing via distinct avenues of heating system configurations. The heat transfer efficiency of the …

Economic Interrelationships And Impacts Of The Aviation/Aerospace Industry In The State Of Florida Using Input-Output Analysis, Kelly A. Whealan-George

Doctoral Dissertations and Master's Theses

The study provided a detailed description of the interrelatedness of the aviation and aerospace industry with principal industries in Florida and Volusia County (VC) using Input-Output (IO) analysis. Additionally, this research provided an economic impact analysis of the creation of a university research park in Daytona Beach (DB). The economic impact measures included not only direct economic output and industry employment descriptions but also described the multiplier effects in the form of indirect and induced impacts using data for 2012.

This research concluded the average labor income of the aviation and aerospace industry was higher than average labor income in …

Cubesat Wakes In The Earth’S Ionosphere, Robert M. Albarran Ii

Doctoral Dissertations and Master's Theses

Space exploration is currently being revolutionized by the advent of the CubeSat: 10cm cubed satellites that typically deploy in constellations for less than $100,000. Spacecraft instrumentation design must be redefined to abide by the compact CubeSat payload. Furthermore, the CubeSat dimension must be considered with respect to characteristic length scales of the space plasma environment, namely, the Debye length. Although spacecraft-plasma interactions- surface charging, plasma sheaths and wakes- have been well-studied for larger satellites, they are less understood for CubeSats.

The Dynamic Ionosphere CubeSat Experiment (DICE) is a 1.5U CubeSat which recently ended its mission. DICE carried two fixed-bias Langmuir …