Impact Of Isolated Atmospheric Aging Processes On The Cloud Condensation Nuclei Activation Of Soot Particles,
2019
Missouri University of Science and Technologoy
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,
2019
Missouri University of Science and Technology
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,
2019
University of Nevada, Las Vegas
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,
2019
University of Alabama in Huntsville
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,
2019
University of Alabama in Huntsville
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,
2019
University of Alabama in Huntsville
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,
2019
Georgia Southern University
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,
2019
University of Alabama in Huntsville
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,
2019
University of Alabama in Huntsville
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,
2019
University of Alabama in Huntsville
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,
2019
Western Michigan University
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,
2019
University of Nebraska-Lincoln
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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,
2019
University of Texas at Arlington
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 …
