Engineering Commons^™

Stability And Power Optimality In Time-Periodic Flapping Wing Structures, Bret Stanford, Philip Beran, Richard Snyder, Mayuresh Patil

United States Air Force: Publications

This paper investigates the nonlinear dynamics of a vehicle with two flexible flapping wings. The body dynamics and the wings' deformation are monolithically grouped into a single system of equations, with aerodynamics accounted for by a quasi-steady blade element method. A periodic shooting method is then used to locate closed orbits of this non-autonomous system, and Floquet multipliers assess the linearized stability about the nonlinear orbit. This framework is then exposed to a gradient based optimizer, in order to quantify the role of wing planform variables, wing structure variables, and kinematic actuation variables in obtaining vehicles with superior open-loop stability …

Turbulence Modeling For Subsonic Separated Flows Over 2-D Airfoils And 3-D Wings, Aaron Michael Rosen

Open Access Theses

Accurate predictions of turbulent boundary layers and flow separation through computational fluid dynamics (CFD) are becoming more and more essential for the prediction of loads in the design of aerodynamic flight components. Standard eddy viscosity models used in many commercial codes today do not capture the nonequilibrium effects seen in a separated flow and thus do not generally make accurate separation predictions. Part of the reason for this is that under nonequilibrium conditions such as a strong adverse pressure gradient, the history effects of the flow play an important role in the growth and decay of turbulence. More recent turbulence …

Direct Flutter And Limit Cycle Computations Of Highly Flexible Wings For Efficient Analysis And Optimization, Bret Stanford, Philip Beran

United States Air Force: Publications

The usefulness of flutter as a design metric is diluted for wings with destabilizing (softening) nonlinearities, as a stable high-amplitude limit cycle (subcritical) may exist for flight speeds well below the flutter point. It is thus desired to design aeroelastic structures such that the post-flutter behavior is as benign (i.e., supercritical) as possible, among the other constraints commonly considered in the optimization process. In order to account for these metrics in an accurate and efficient manner, direct tools are utilized to first locate the Hopf-point (flutter speed), and then to obtain a nonlinear perturbation solution via the method of multiple …

Effect Of Aviation Fuel Type And Fuel Injection Conditions On The Spray Characteristics Of Pressure Swirl And Hybrid Air Blast Fuel Injectors, Rick Thomas Feddema

Open Access Theses

Feddema, Rick T. M.S.M.E., Purdue University, December 2013. Effect of Aviation Fuel Type and Fuel Injection Conditions on the Spray Characteristics of Pressure Swirl and Hybrid Air Blast Fuel Injectors. Major Professor: Dr. Paul E. Sojka, School of Mechanical Engineering

Spray performance of pressure swirl and hybrid air blast fuel injectors are central to combustion stability, combustor heat management, and pollutant formation in aviation gas turbine engines. Next generation aviation gas turbine engines will optimize spray atomization characteristics of the fuel injector in order to achieve engine efficiency and emissions requirements.

Fuel injector spray atomization performance is affected by the …

Effects Of Strain Energy Release Rate On Delamination In Temperature Environment, Venkata Naga Ravitej Sankarabatla

Mechanical and Aerospace Engineering Theses - Archive

Delamination is the weakest and major failure mode in laminated composites. Extensive efforts on initiation and growth of delamination under mechanical load have been investigated. A little emphasis was made earlier to account for the delamination in laminates under temperature loading. Strain energy release rate, a fracture mechanics parameter has been widely accepted to use for study the characteristics of delamination growth. In order to conduct a quick assessment of delamination growth, a closed form expression is developed to quantify the strain energy release rate of the laminate subjected to temperature environment. A finite element model is also developed to …

Investigation Of Side Wall Effects On An Inward Scramjet Inlet At Mach Number 8.6, Tiago Cavalcanti Rolim

Mechanical and Aerospace Engineering Dissertations - Archive

Experimental and computational studies were conducted to evaluate the performance of a scramjet inlet as the side cowl length is changed. A slender inward turning inlet with a total length of 304.8 mm, a span of 50.8 mm with a top and a bottom compression ramp each at 11.54 deg and a compression ratio of 4.79 was used. The side cowl lengths were of 0, 50.8 and 76.2 mm. The UTA Hypersonic Shock Tunnel facility was used in the reflected mode to test the inlet model. The model was instrumented with nine piezoelectric pressure transducers, for static and total pressure …

Development Of Artificial Neural Network Based Black Box Model Of A Data Center As A Temperature Predicting Tool As A Function Of Server Location, Dissipating Server Heat And Crac Fan Speed, Chinmay N. Date

Mechanical and Aerospace Engineering Theses - Archive

Modern data centers consume an astonishing 1.3\% power all around the world. As the number of data centers continue to grow, there is an increasing need and demand to develop new ways to reduce the power footprint. Several approaches are being made to achieve this. One of such several approaches is to develop control systems that would keep the data centers running energy efficiently. Various control theories have been developed throughout the world to achieve the optimal energy efficient state. However, during the synthesis of such control schemes, the CFD simulations take up excessive time for plotting the thermal map …

Development Of Multi-Element Active Aerodynamics For The Formula Sae Car, James Patrick Merkel

Mechanical and Aerospace Engineering Theses - Archive

This thesis focuses on the design, development, and implementation of an active aerodynamics system on 2013 Formula SAE car. The aerodynamics package itself consists of five element front and rear wings as well as an under body diffuser. Five element wings produce significant amounts of drag which is a compromise between the cornering ability of the car and the acceleration capability on straights. The active aerodynamics system allows for the wing angle of attack to dynamically change their configuration on track based on sensory data to optimize the wings for any given scenario. The wings are studied using computational fluid …

The Samara Spacecraft: Design And Development Of A Self-Stabilizing, Auto-Rotating, Distributed Sensing System, Amit Desai Lalloobhai

Mechanical and Aerospace Engineering Theses - Archive

The scope of this research is the design and development of a self-stabilizing re-entry vehicle that closely resembles naturally occurring seeds in nature. It was hypothesized that a femto-satellite with a shape of a samara could self stabilize and passively generate lift, as well as transmit a signal during its descent through the atmosphere. The research included a conceptual design phase and a preliminary design phase that entailed analytic simulations, and an experimental demonstration. The goal was to investigate the feasibility of developing the above-mentioned femto-vehicle that could increase the range capability of its descent to maximize data capture.

Development And Operation Of An Integrated Sampling Probe And Gas Analyzer For Turbulent Mixing Studies In Complex Supersonic Flows, John D. Wiswall

Mechanical and Aerospace Engineering Theses - Archive

For many aerospace applications, mixing enhancement between co-flowing streams has been identified as a critical and enabling technology. Due to short fuel residence times in scramjet combustors, combustion is limited by the molecular mixing of hydrogen (fuel) and air. Determining the mixedness of fuel and air in these complex supersonic flowfields is critical to the advancement of novel injection schemes currently being developed at UTA in collaboration with NASA Langley and intended to be used on a future two-stage to orbit (~Mach 16) hypersonic air-breathing vehicle for space access.Expanding on previous work, an instrument has been designed, fabricated, and tested …

Numerical Study Of Incompressible Fluid Flow In A Vertically Dropping Pool With And Without End Sill, Vimal Ramanuj

Mechanical and Aerospace Engineering Theses - Archive

The study involves numerical analysis of flow field for three different flow regimes taking place in a vertically dropping pool. In general, a vertically dropping flow generates a skimming flow regime with one recirculation zone along with a developing shear layer. The presence of an obstacle (end sill) results in the formation of another recirculation zone downstream of the impinging jet. Based on the nature of these zones, the flow is categorized as napped, periodically oscillatory and skimming. The type of flow regime depends on the flow parameters like velocity and depth of flow which are controlled by Froude number. …

3-D Fracture Study Of The Beol Cu/Low-K Stack To Assess And Mitigate The Cpi Risk During The Reflow Process, Zaeem Baig

Mechanical and Aerospace Engineering Theses - Archive

As scaling of components continues, using SiO2 as a dielectric in the Back-End-Of-Line (BEoL) is no longer a viable option and can be replaced with low-k and ultralow-k (ULK) dielectric materials for advanced integrated circuits (IC) packaging solutions. The low-k materials improve performance by reducing parasitic capacitance and crosstalk between adjacent metal lines. However, low-k dielectrics have lower modulus, lower fracture toughness, higher coefficient of thermal expansion (CTE), and poor adhesion as compared to SiO2. Thus, low-k dielectric integration in the contemporary IC packages poses a significant reliability challenge. Delamination along the metal-dielectric interfaces and crack propagation in the dielectric …

A Novel Approach For Two-Dimensional Inclusion/Hole Problems Using The Airy Stress Function Method, Manikandan Madhavan

Mechanical and Aerospace Engineering Theses - Archive

This thesis demonstrates the application of the Airy stress function in solving plane elasticity problems. An Airy stress function is determined for two-dimensional infinite plates containing a circular inclusion embedded with a circular hole subjected to tensile loading and the traction and displacement functions for various boundary conditions satisfy the equilibrium and continuity conditions. Mathematica was useful for solving the complex expressions and to calculate the elastic fields for a variety of elastic problems in this study.

Modeling The Dynamic Behavior Of Estrogen Docking Into Its Receptor Using The Multiscale Analysis, Anudeep Palanki

Mechanical and Aerospace Engineering Theses - Archive

This work models the dynamic behavior of Estrogen docking into its receptor. It lays the foundation for the development of a new theoretical screening technique to identify carcinogens. It is predicted that this year, more than 1 million Americans and more than 10 million people worldwide will be diagnosed with cancer. Only 5 to 10 percent of all cancer cases can be attributed to genetic defects, whereas the remaining 90 to 95 percent have their roots in the environment. It has been suggested that some chemical compounds have a similar structure and properties as natural hormones produced by the human …

Utilization Of Microencapsulated Phase Change Material For The Optimization Of Evaporative Cooling Technology, Jeet Shah

Mechanical and Aerospace Engineering Theses - Archive

IT equipments are the essential facet of most institutional operations of the advanced world. Modern IT equipments are far more vigorous than older equipments. With increasing density of array of servers and growth of computing power, assessing the cooling requirements has emerged as an aspect of prime importance. Evaporative cooling is a very common cooling technology used in cooling of data centers due to low installation and power costs and simple operation. Phase change materials have been investigated over the years as thermal energy storage for cooling and heating applications. These researches have also investigated encapsulated PCM in different sizes …

Structural Analysis At Aircraft Conceptual Design Stage, Reza Mansouri

Mechanical and Aerospace Engineering Theses - Archive

In the past 50 years, computers have helped by augmenting human efforts with tremendous pace. The aircraft industry is not an exception. Aircraft industry is more than ever dependent on computing because of a high level of complexity and the increasing need for excellence to survive a highly competitive marketplace. Designers choose computers to perform almost every analysis task. But while doing so, existing effective, accurate and easy to use classical analytical methods are often forgotten, which can be very useful especially in the early phases of the aircraft design where concept generation and evaluation demands physical visibility of design …

Numerical Simulations Of Transonic Wingtip, Suparat Chanrith

Mechanical and Aerospace Engineering Theses - Archive

This report presents numerical simulations using ANSYS FLUENT for a NACA 0012 wing both in two- and three-dimensional cases to compare with an experimental data. This comparison also allowed for any wall interference in wind tunnels to be examined. Moreover, the report also presents numerical simulation of a NACA 0012 wingtip. The simulations were conducted at Mach 0.5, 0.7, 0.75, and 0.8 at various chord Reynolds number and the angle of attack of 0, 2, 4, and 5. The numerical andexperimental data were in good agreement for the full wing and the wingtip cases.

Experimental Study On The Effects Of Gaseous Contamination On It Equipment, Rahul Srinivas Raghunathan

Mechanical and Aerospace Engineering Theses - Archive

Every company is trying to reduce their carbon footprint in today's world. The data center industry is no different. To reduce the cooling costs and increase the efficiency, air -side economizers are used. Air-side economizers bring in outside ambient cold air to cool the data center equipment. Through this, we can save on cooling costs. The problem relating to air-side economization is that we have no control over the humidity and contamination. Humidity and contamination go hand in hand, as one influence the other. In the past filters have been used to combat contamination but it has proved to be …

Development Of Foil Thrust Bearing Test Rig, Rohit Harishchandra Yadav

Mechanical and Aerospace Engineering Theses - Archive

Oil lubricated bearings have been widely used in variety of turbo machinery, though it has its own limitations such as thermal degradation of oil over temperature, complicated oil lubrication system and their maintenance. Commercial application of the air foil bearing (AFB) in Microturbomachinery have been acknowledged. Microturbomachinery term is used in applications with shaft power less than 1000KW and shaft diameter less than 100mm. Microturbomachinery has demanded light weighted, compact, extreme temperature and high speed operation. DN number for oil lubricated bearings and rolling element bearings is very less when compared to foil bearings. Absence of external pressurizing and lubricating …

Point Measurement Of Detonation Wave Propagation Using Ion Guage, Nitesh Karpakala Manjunatha Gupta

Mechanical and Aerospace Engineering Theses - Archive

Accurate measurement of detonation wave velocity is important in the study of detonations. Detonation wave velocity is calculated by the ratio of distance between two transducers which the wave front travels over the propagation time. Conventional methods included transducers placed a few cm apart thereby yielding an average velocity of the wave. A gauge was developed in which the transducers were placed a few mm apart so that an effective point measurement of velocity can be determined. Different types of sensors used in determining the detonation wave velocity included pressure, flame and ion. Of the three, the ion sensor was …

Effect Of Nanoparticle Dispersions In A Binary Nitrate Salt As Thermal Energy Storage Material In Concentrated Solar Power Applications, Bharath Dudda

Mechanical and Aerospace Engineering Theses - Archive

Despite the huge improvements in the field of solar energy to produce electricity, the high cost of production has been one of the major problems in this field. Concentrated solar power (CSP) uses a number of mirrors to concentrate solar radiant energy onto a single focal point. Electrical power is produced when the concentrated light is converted to heat, which drives a heat engine connected to an electrical power generator. This heat is first stored in a thermal energy storage (TES) and transferred to a heat engine to be converted to electricity and thus TES can provide heat even after …

Utilization Of Molten Nitrate Salt Nanomaterials For Heat Capacity Enhancement In Solar Power Applications, Ramaprasath Devaradjane

Mechanical and Aerospace Engineering Theses - Archive

Concentrated solar power (CSP) system use general thermodynamic cycle to produce electricity and thus the system efficiency is mainly determined by the working temperature of heat transfer fluid (HTF). Organic-based HTFs (e.g., mineral oil, ethylene glycol, etc.) were firstly used for this application. However, this has limited the working temperature of CSP around 300 °C since these organic material starts to decompose below 400 °C. Typical liquid salts are thermally stable to high temperatures (500~600 °C). Using these salts as HTF can significantly increase the working temperature and as a result the system efficiency can also be highly enhanced. For …

Design And Analysis Of A Compression Molded Carbon Composite Wheel Center, Vinoth Kumar Dhananjayan

Mechanical and Aerospace Engineering Theses - Archive

Importance of closed mold and short fibers in the manufacture of carbon composite parts was realized based on a study of existing manufacturing processes for thermoset resins as these can improve production volumes, cost reduction of the part, production of near net shape parts eliminating secondary operations and production of parts with near isotropic properties due to random fiber orientation. Compression molding process is the most preferred process as this addresses the problems of fiber damage effectively because of the minimal flow in the material. A brief study was done on the compression molded carbon composite parts in the industry. …

Integrated Modeling Approach For Solid Oxide Fuel Cell-Based Power Generating System, Jeongpill Ki

Mechanical and Aerospace Engineering Dissertations - Archive

Solid oxide fuel cell (SOFC) systems have been recognized as the most advanced power generation system with the highest thermal efficiency with a compatibility with a wide variety of hydrocarbon fuels, synthetic gas from coal, hydrogen, etc. As a result of research focused on numerical studies for a tubular type- or a planar type-SOFC, fuel flexibility, design aspects of SOFC, materials, start-up process, and so on, SOFC technologies are remarkably being developed.Currently, most research activities are limited to a component level characterization of single fuel cell stack or material research for catalyst, electrolyte, sealing process, etc. In other words, approaches …

Development Of Computational Fluid Dynamics (Cfd) Based Erosion Models For Oil And Gas Industry Applications, Deval Pandya

Mechanical and Aerospace Engineering Dissertations - Archive

Erosion prediction plays a critical role in different oil and gas industry segments including drill bit manufacturing, measurement & logging while drilling (M&LWD), and reservoir engineering/completions tools. Recently, Computational Fluid Dynamics (CFD) is used to predict erosion due to multiphase flows in complex geometries. Currently used CFD-based erosion models are able to predict erosion regions fairly accurately in various applications but they are highly inaccurate when it comes topredictions of quantities like erosion rate. Predicted quantities within an order of magnitude of the measured values are common and may be considered acceptable for many applications in the industry simply because …

Advanced Materials Characterization Based On Full Field Deformation Measurements, A Paige Carpentier

Mechanical and Aerospace Engineering Dissertations - Archive

Accurate stress-strain constitutive properties are essential for understanding the complex deformation and failure mechanisms for materials with highly anisotropic mechanical properties. Among such materials, glass-fiber- and carbon-fiber-reinforced polymer-matrix composites play a critical role in advanced structural designs. The large number of different methods and specimen types currently required to generate three-dimensional allowables for structural design slows down the material characterization. Also, some of the material constitutive properties are never measured due to the prohibitive cost of the specimens needed. This work shows that simple short-beam shear (SBS) specimens are well-suited for measurement of multiple constitutive properties for composite materials and …

Multi-Objective Design Optimization Of Beol/Fbeol Region During Chip Attachment To Substrate, Hardik Parekh

Mechanical and Aerospace Engineering Theses - Archive

Semiconductor industry has recognized the need to replace traditional Al/SiO2 interconnects with Cu/Low-k interconnects in the mainstream electronics devices following the latter's impact on power, RC delay, and cross-talk reduction. However due to lower elastic modulus, strength, and poor adhesion characteristic, reliability of the Cu/Low-k interconnects turns out to be a concern for its integration in the back-end-of-line (BEoL). Flip-chip attachment process (cooling from ~200C to room) can result in critical damage in nano-scale Cu/Low-k interconnects. The objective of this study is to improve the reliability of Cu/Low-k interconnects during die attach reflow process for a specific die to substrate …

Design And Control Of A Smart Bed For Pressure Ulcer Prevention, Zachary Govier Brush

Mechanical and Aerospace Engineering Theses - Archive

This work details the design, simulation, and experimental testing of a mechanically actuated smart hospital bed for the prevention of pressure ulcers in hospital patients. The smart hospital bed, or Smartbed, is designed to improve the “turning” process currently performed by health care workers, ensuring that patients are turned consistently and decreasing the labor requirement for caregivers. The mechanical structure of the bed is described, along with its advantages over current Smartbed products. Next, dynamic models of the Smartbed actuating systems are discussed along with descriptions of the devised single-unit and overall bed control systems. The control equations determined in …

Design And Evaluation Of A Chemical Reactor For The Pyrolysis Wood Pellets, Pawarat Bootpakdeetam

Mechanical and Aerospace Engineering Theses - Archive

Currently there is interest in converting waste biomass into valuable products, such as fuels and specialty chemicals. However, the product composition, yield, the energy required to run the reaction, and the required residence time are all factors influence the economics of the process. Estimate of these factors at the laboratory scale is important for evaluating whether a pilot or demonstration scale study is warranted. In this work, a bench-scale chemical reactor was designed and constructed to conduct the batch pyrolysis of pelletized biomass. The reactor was tested using pine wood pellets as the feedstock. The feedstock weight to reactor volume …

Optimal Design Of Beams, Shivakumar Samala

Mechanical and Aerospace Engineering Theses - Archive

Beams are basic structural components that are capable of withstanding load primarily by resisting bending. Unlike Euler-Bernoulli beams, Timoshenko beams undergo both shear deformation and rotational effects, making it suitable for analyzing the behavior of thick or short beams, composite beams and beams that are subjected to high frequency excitation when their wave length becomes shorter. This thesis work focuses on optimal design of straight and tapered Timoshenko beams under static and dynamic constraints for rectangular and circular cross sections. In this work Timoshenko beam static and dynamic equations were studied. The finite element method was used for static and …