Aerospace Engineering Commons^™

An Experimental And Numerical Study Of High Temperature Gaseous Flow Through An Open Cell Silicon Carbide Foam Heater, Denis Pansolin

LSU New Orleans Theses and Dissertations

No abstract provided.

Impact Of Isolated Atmospheric Aging Processes On The Cloud Condensation Nuclei Activation Of Soot Particles, Franz Friebel, Prem Lobo, David Neubauer, Ulrike Lohmann, Saskia Drossaart Van Dusseldorp, Evelyn Mühlhofer, Amewu A. Mensah

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act …

Bubble Pinch-Off In Turbulence, Daniel J. Ruth, Wouter Mostert, Stephane Perrard, Luc Deike

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Although bubble pinch-off is an archetype of a dynamical system evolving toward a singularity, it has always been described in idealized theoretical and experimental conditions. Here, we consider bubble pinch-off in a turbulent flow representative of natural conditions in the presence of strong and random perturbations, combining laboratory experiments, numerical simulations, and theoretical modeling. We show that the turbulence sets the initial conditions for pinch-off, namely the initial bubble shape and flow field, but after the pinch-off starts, the turbulent time at the neck scale becomes much slower than the pinching dynamics: The turbulence freezes. We show that the average …

Performance Modeling Of Supercritical Carbon Dioxide Zigzag-Channel Printed Circuit Heat Exchangers, Katrine Birgitte Bennett

UNLV Theses, Dissertations, Professional Papers, and Capstones

Supercritical carbon dioxide (sCO2) is currently being studied as the working fluid in power producing Brayton cycles due to its excellent physical and thermodynamic properties, especially near the critical point. Printed circuit heat exchangers (PCHEs) are being considered for use as condensers and recuperators for this purpose due to their high strength and compact designs. Many experimental and numerical studies are being conducted to characterize and optimize sCO2 PCHE operation and develop correlations to describe their thermal-hydraulic performance. Additionally, a few experimental and numerical structural assessments of these PCHEs have been conducted, but all have been somewhat limited due to …

Double Wall Cooling Of An Effusion Plate With Simultaneous Cross Flow And Impingement Jet Array Internal Cooling, Phil Ligrani, Austin Click, David Ritchie, Federico Liberatore, Rajeshriben Patel, Yin-Hsiang Ho

PRC-Affiliated Research

The present study considers comparisons of hot-side effusion plate results for a mainstream flow passage with CR = 1 and for a mainstream flow passage with CR = 4. The coolant supply arrangement for both CR contraction ratio values includes simultaneous use of cross flow and an impingement jet array. For the effusion cooled/hot surface, presented are spatially-resolved distributions of surface adiabatic film cooling effectiveness, and surface heat transfer coefficients (measured using infrared thermography). These results are given for main flow Reynolds numbers Rems of 89,900 to 95,800. For this main flow Reynolds number range, four different combination values of …

Double Wall Cooling Of An Effusion Plate With Simultaneous Cross Flow And Impingement Jet Array Internal Cooling, Phil Ligrani, Austin Click, David Ritchie, Federico Liberatore, Rajeshriben Patel, Yin-Hsiang Ho

PRC-Affiliated Research

The present study considers comparisons of hot-side effusion plate results for a mainstream flow passage with CR = 1 and for a mainstream flow passage with CR = 4. The coolant supply arrangement for both CR contraction ratio values includes simultaneous use of cross flow and an impingement jet array. For the effusion cooled/hot surface, presented are spatially-resolved distributions of surface adiabatic film cooling effectiveness, and surface heat transfer coefficients (measured using infrared thermography). These results are given for main flow Reynolds numbers Rems of 89,900 to 95,800. For this main flow Reynolds number range, four different combination values of …

Double Wall Cooling Of An Effusion Plate With Simultaneous Cross Flow And Impingement Jet Array Internal Cooling, Phil Ligrani, Austin Click, David Ritchie, Federico Liberatore, Rajeshriben Patel, Yin-Hsiang Ho

PRC-Affiliated Research

The present study considers comparisons of hot-side effusion plate results for a mainstream flow passage with CR = 1 and for a mainstream flow passage with CR = 4. The coolant supply arrangement for both CR contraction ratio values includes simultaneous use of cross flow and an impingement jet array. For the effusion cooled/hot surface, presented are spatially-resolved distributions of surface adiabatic film cooling effectiveness, and surface heat transfer coefficients (measured using infrared thermography). These results are given for main flow Reynolds numbers Rems of 89,900 to 95,800. For this main flow Reynolds number range, four different combination values of …

The Investigation Of Noise, Vibrations And Emissions Of Aero-Gas Turbine Combustion With Synthetic Kerosene Fuels, Margaret Kilpatrick

Honors College Theses

Climatic changes from aviation emissions are complex and include effects of greenhouse gases such as: CO2, NOx, and aerosols. For that reason, the objectives of this study were to investigate the noise, vibrations and emissions characteristics of synthetic kerosene combustion in an aerospace gas turbine to reduce the engine’s environmental impact. Sustainably produced synthetic kerosene is known for having low soot emissions due to little to no aromatics (compounds that create particle pollutants), and for being a sustainable alternative fuel source to imported oil. The noise and sound levels were collected using Bruel & Kjaer microphones to measure various mid …

Analysis Of Shock Wave Unsteadiness Using Space And Time Correlations Applied To Shadowgraph Flow Visualization Data, Shannon Marko, Phillip M. Ligrani

PRC-Affiliated Research

Unsteady flow characteristics of a normal shock wave, a lambda foot, and a separated turbulent boundary layer are investigated within a unique test section with supersonic inlet flow. The supersonic wind tunnel facility, containing this test section, provides a Mach number of approximately 1.54 at the test section entrance. Digitized shadowgraph flow visualization data are employed to visualize shock wave structure within the test section. These data are analyzed to determine shock wave unsteadiness characteristics, including grayscale spectral energy variations with frequency, as well as time and space correlations, which give coherence and time lag properties associated with perturbations associated …

Analysis Of Shock Wave Unsteadiness Using Space And Time Correlations Applied To Shadowgraph Flow Visualization Data, Shannon Marko, Phillip M. Ligrani

PRC-Affiliated Research

Unsteady flow characteristics of a normal shock wave, a lambda foot, and a separated turbulent boundary layer are investigated within a unique test section with supersonic inlet flow. The supersonic wind tunnel facility, containing this test section, provides a Mach number of approximately 1.54 at the test section entrance. Digitized shadowgraph flow visualization data are employed to visualize shock wave structure within the test section. These data are analyzed to determine shock wave unsteadiness characteristics, including grayscale spectral energy variations with frequency, as well as time and space correlations, which give coherence and time lag properties associated with perturbations associated …

Analysis Of Shock Wave Unsteadiness Using Space And Time Correlations Applied To Shadowgraph Flow Visualization Data, Shannon Marko, Phillip M. Ligrani

PRC-Affiliated Research

Unsteady flow characteristics of a normal shock wave, a lambda foot, and a separated turbulent boundary layer are investigated within a unique test section with supersonic inlet flow. The supersonic wind tunnel facility, containing this test section, provides a Mach number of approximately 1.54 at the test section entrance. Digitized shadowgraph flow visualization data are employed to visualize shock wave structure within the test section. These data are analyzed to determine shock wave unsteadiness characteristics, including grayscale spectral energy variations with frequency, as well as time and space correlations, which give coherence and time lag properties associated with perturbations associated …

Methodology Of Topology Optimization, Naziha Khandoker

Honors Theses

The need for lighter products is becoming increasingly essential as it cuts material cost and significant amount of weight, which is a key factor in the automotive and aerospace industries. Topology optimization allows us to achieve that by applying the concept to different structures with the goal of optimal distribution of material within finite volume design domain. Its algorithms selectively remove and relocate elements to achieve the optimum performance. This project performs a study on the effect of each design parameter over mechanical performance using Finite Element Analysis and applies it to set of wing attachment brackets. The optimized brackets …

Multiscale Modeling Of Fracture In Quasi-Brittle Materials Using Bifurcation Analysis And Element Elimination Method, Keyvan Zare Rami

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Analyzing the fracture of heterogeneous materials is a complex problem, due to the fact that the mechanical behavior of a heterogeneous material is strongly dependent on a variety of factors, such as its microstructure, the properties of each constituent, and interactions between them. Therefore, these factors must be effectively taken into account for accurate analysis, for which the multiscale method has been widely used. In this scheme, the computational homogenization method is used to obtain the effective macroscopic properties of a heterogeneous material based on the response of a Representative Volume Element (RVE). The growth of damage in an RVE …

Pulsed Detonation Engine Nozzle Design And Analysis, Rahul Kumar

Mechanical and Aerospace Engineering Dissertations - Archive

For a hypersonic flight mission, different flight regimes have been recognized. The successful and efficient operation of the aircraft to traverse through all the flight regimes requires the integration of various propulsion cycles into a single flow path. Using the phenomenon of detonation initiation and propagation, a multi-mode detonation based propulsion concept was proposed for hypersonic flight. Of the different modes proposed, it was recognized that the efficient operation of Normal Detonation Wave Engine (NDWE) mode and Oblique Detonation Wave Engine (ODWE) mode played an important role as they delivered thrust at critical parts of the trajectory. For this study, …

Improving Compressive Strength Of High Modulus Carbon-Fiber Reinforced Polymeric Composite With Varying Modulus Fibers, Sarvenaz Ghaffari

Mechanical and Aerospace Engineering Dissertations - Archive

There has been a strong demand in using high-modulus (HM) carbon-fiber composites potentially enabling lightweight aircraft structures with significant weight savings. However, extremely low fiber-direction compressive strength has been a well-recognized weakness of the HM composites, preventing their implementation in aircraft platforms. Fiber-direction compressive strength of HM and intermediate-modulus (IM) carbon fiber-reinforced polymers (CFRP’s) is presumably governed by microstructural stability. However, strong decrease in fiber-direction compressive strength of HM carbon-fiber composites, compared to their intermediate modulus (IM) counterparts, contradicts predictions from available microstructural buckling theories. A recent work demonstrated that significant improvement in the fiber-direction compressive strength of HM carbon-fiber …

Numerical Study Of Detonation Flame Arrestor Performance And Detonation Interaction With The Arrestor Element, Hoden Ali Farah

Mechanical and Aerospace Engineering Dissertations - Archive

A numerical study of detonation propagation and interaction with a flame arrestor product in a combustible gas/vapor transport pipeline system is conducted. The flame arrestor element is modeled as a porous medium using the Forchheimer equation, which is incorporated in the governing conservation equations as a momentum sink. The Forchheimer porous medium model is then used to model the flow through a representative four-inch detonation flame arrestor and is validated with experimental data. The detonation propagation simulation is modeled with the Reynolds averaged Navier-Stokes (RANS) equations extended for reacting flow. A 21-step chemical kinetic mechanism with 10 species is used …

Numerical Study Of High–Frequency Fluidic Valve Injectors For Detonation Engine Applications, Sushma Yalavarthi

Mechanical and Aerospace Engineering Dissertations - Archive

The feasibility of fluidic valves for use in detonation-based engines was studied numerically. The fluidic valve acted by shutting off reactant flow through the high pressure behind detonation waves propagating past the valve opening. The valve which featured a plenum cavity was mounted to the side of a pulsed detonation engine, an arrangement that allowed the valve to be characterized under a sustained operation. A series of different cavity lengths were studied. Further, a numerical study of the high-frequency fluidic valve was conducted by using a two-dimensional reactive Euler solver. A 19–step elementary mechanism was employed for the stoichiometric oxyhydrogen …

Dynamics Of A Pulse Detonation Engine Driven Linear Power Generator, Umang Umeshkumar Dighe

Mechanical and Aerospace Engineering Dissertations - Archive

The dynamics of a pulse detonation engine driven linear power generator were studied. For an ideal pulse detonation engine, the thrust generated is in the form of a piecewise function given by the Endo-Fujiwara model. Nonlinear electromagnetic damping is also introduced in the system due to the rare earth permanent magnets present in the linear generator architecture. Various linear generator topologies were studied using static magnetic analysis. Two configurations of a single degree-of-freedom oscillator system, one with a linear spring restoring force and another with geometric nonlinear spring restoring force, were investigated to study any potential advantages of using nonlinear …

Droplet-Based Microextraction Of Dna Enabled By Electrowetting-On-Dielectric Digital Microfluidics, Shubhodeep Paul

Mechanical and Aerospace Engineering Dissertations - Archive

In recent years there have been significant advances in micro/nanotechnologies employing miniaturized platforms to achieve efficient sample pre-processing, separation, and quantification processes. The idea of bringing several lab-scale protocols on to a single chip, i.e., a lab-on-a-chip (LOC) device along with automation, is a reality now. Miniaturization of biochemical operations usually handled in a laboratory has numerous advantages, such as cost effectiveness, multiplexing, assay speed, and sensitivity. Microfluidic technologies used in LOC devices can manipulate tiny volumes of samples and reagents to perform on-chip protocols with minimal human intervention. Electrowetting-on-dielectric (EWOD)-based digital microfluidics (DMF) is one of the LOC platforms …

Assessment Of Material State In Composites Using Global Dielectric State Variable, Vamsee Vadlamundi

Mechanical and Aerospace Engineering Dissertations - Archive

Composites are heterogeneous in nature and a fundamental understanding of the material response to applied mechanical, thermal, electrical and other multi-physical fields is required to efficiently design and synthesize the material system and demands attention to long-term behavior in particular. Unlike metals, composites are designed to develop distributed damage and initiation of a single microscopic crack does not individually affect the strength/life of these materials. Therefore, the primary interest is not in single local events but in the process of interaction of multiple events that have a collective global effect on the material behavior. The interaction of these local events …

Development And Testing Of A Control Strategy For Dynamic Cooling At Rack Level In Data Centers, Amrutha Valli Rachakonda

Mechanical and Aerospace Engineering Theses - Archive

Cooling is a critical part of data center’s infrastructure, and with ongoing demands in data processing and storage, thermal management issues are of great concern. Some imperative methods of removing heat are either using air or liquid (preferably water or refrigerant). When high power density modules are involved, liquid cooling addresses some of the problems faced by air cooling as liquid coolants have higher thermal capacitance. Also, in the case of multi-chip modules, a non-uniform heating due to multi-core generates hot-spots and increases temperature gradients across the module. A dynamic cold plate along with a self-regulated flow control device was …

Autonomous Carrier Landing Of A Fixed-Wing Uav With Airborne Deck Motion Estimation, Metin Kus

Mechanical and Aerospace Engineering Theses - Archive

This study focuses on the design, implementation, and evaluation of an autonomous carrier landing system featuring an airborne deck motion estimation module. The three-dimensional dynamics of a fixed-wing UAV with the actuator and engine dynamics are considered. A carrier motion model that accounts for the perturbations caused by various sea states is built. An airborne measurement system, which is composed of a calibrated camera and light-emitting beacons, is utilized to detect several coplanar target points on the moving carrier deck. The known correspondence between the locations of the target points and their coordinates on the focal plane of the camera …

Static Response Calibration Of 3d Printed Thin Walled Structures Using Fused Deposition Modelling, Akhilesh Ravindra Kulkarni

Mechanical and Aerospace Engineering Theses - Archive

3-D printing has enabled flexible, tool-less fabrication that yields numerous benefits. One benefit is unique and complex structural arrangements that increase design freedom to minimize weight. Such arrangements can be guided by advanced topology, shape, and sizing optimization tools using appropriate process constraints to ensure a printable design and can include highly integrated structural details such as stiffeners, flanges, frames, and other connections. 3D printing thin wall aircraft structures presents challenges for material and structural characterization. 3D printing enables integrated structural details, each detail is affected by the print process capability to fabricate the local geometry and deviations from designed …

Backstepping Approach For Design Of Cascaded Pid Controller With Guaranteed Trajectory Tracking Performance For Micro-Air Uav, Yusuf Kartal

Mechanical and Aerospace Engineering Theses - Archive

Flight controllers for micro-air UAVs are generally designed using Proportional- Integral-Derivative (PID) methods, where the tuning of gains is difficult and time-consuming, and performance is not guaranteed. In this thesis, we develop a rigorous method based on the sliding mode analysis and nonlinear backstepping to design a PID controller with guaranteed performance. This technique provides the structure and gains for the PID controller, such that a robust and fast response of the UAV for trajectory tracking is achieved. First, the second-order sliding variable errors are used in a rigorous nonlinear backstepping design to obtain guaranteed performance for the nonlinear UAV …

Analysis Of Laminated Curved Beam With And Without Defects And Imperfections, Wei-Tsen Lu

Mechanical and Aerospace Engineering Dissertations - Archive

Several studies have focused on the modeling and response characterization of composite structural members, with particular emphasis on composite curved beams. The class of curved beam is explored to determine mechanical response in primary aerospace structural applications. The present work focuses on developing analytical closed-form solutions for investigating composite curved beams with and without fiber waviness and delamination. The present work can efficiently characterize the structural behavior of composite curved beams under bending. This work shows the development of a novel mathematical approach to predict structural performance by investigating axial stiffness, bending stiffness with consideration of shear deformation in composite …

Electrowetting-On-Dielectric (Ewod) Digital Microfluidic Device For Synthetic Organic Chemistry, Matin Torabinia

Mechanical and Aerospace Engineering Dissertations - Archive

Over the past decades, microscale chemical reaction technology has been attractive in diverse areas of chemistry. It allows the precise control of quantified reagents and highly efficient heat and mass transfer, because of a large interface-to-volume ratio–particularly in case of the exothermic reaction and mixing–, reduced consumption of toxic or expensive agents, improved reaction profiles, and enhanced selectivity compared to macro-scale reactions. The mainstream microscale reaction processes were established using continuous microchannel flow systems, which has emerged as a powerful complement to batch chemistry on the laboratory scale due to relative advantages, some of which include: increased safety, more accurate …

An Implementation Of The Regularized Extended Finite Element Method In Abaqus, Yu-Jui Liang

Mechanical and Aerospace Engineering Dissertations - Archive

The Regularized eXtended Finite Element Method (Rx-FEM) methodology is a discrete damage modeling (DDM) technique, which represents an approach to the progressive damage analysis (PDA) in laminated composites when multiple damage events such as matrix cracks and delamination are introduced into the model via the displacement discontinuities. In the Rx-FEM, the Heaviside step function that is typically used to introduce a displacement discontinuity across a crack surface in the eXtended Finite Element Method (x-FEM) is replaced by a continuous function approximated by using the finite element (FE) shape functions. This regularization offers unique possibility for the implementation of the Rx-FEM …

Material Characterization And Fracture Prediction Of Fdm Printed Parts, Sanchita Sheth

Mechanical and Aerospace Engineering Theses - Archive

In order to take advantage of the design freedom that Additive Manufacturing offers, most applications require reliable material characterization. This can ensure that a design performs within its environment and life requirements. This work discusses two models. One investigates the raster angle dependency of stiffness properties and the other numerically predicts fracture in Fused Deposition Modeling (FDM) printed polymer parts. Pre-processing of FDM geometry was done in Abaqus CAE (SIMULIA TM). FEA and post-processing was done in BSAM, which is a damage prediction software developed for composites. BSAM uses a regularized extended finite element approach of Discrete Damage Modeling. In …

A Robust Controller Design For A Tailless Uav With Effective Control Allocation, Ethem Hakan Orhan

Mechanical and Aerospace Engineering Theses - Archive

Attempts to completely remove the tails from aircraft can be dated back to the early days of modern aviation. A number of stability and control problems arising from the unique characteristics of the configuration resulted in poor handling qualities and some dangerous flight characteristics in the early designs. Lately, this configuration is becoming widespread again and the current state-of-the-art of fly-by wire technology and modern control design techniques enable design of tailless aircraft which are safe to fly. In this thesis, a study on the application of modern robust control design techniques on a tailless UAV is presented. A nonlinear …

Estimation Of The Fatigue Life Of Additively Manufactured Metallic Components Using Modified Strain Life Parameters Based On Surface Roughness, Peter Grohs

Masters Theses

In this study, a method is developed to estimate the effects of surface roughness on the fatigue life of additively manufactured titanium Ti6Al4V, aluminum 7075–T6, and steel 4340 alloys through modified strain life parameters using finite element analysis (FEA). This method is highly beneficial to the fatigue analysis of as-built additively manufactured metal components, which possess rough surfaces that reduce fatigue life significantly but are challenging to analyze directly using finite element simulation because of complex geometries, i.e., modeling an exact surface profile is arduous.

An effective stress concentration factor, incorporating roughness data, is defined to quantify their effects on …