Computational Engineering Commons^™

Experimental Investigation Of Mist Film Cooling And Feasibility Study Of Mist Transport In Gas Turbines, Reda M. Ragab

University of New Orleans Theses and Dissertations

In the modern advanced gas turbines, the turbine inlet temperature may exceed 1500°C as a requirement to increase power output and thermal efficiency. Therefore, it is imperative that the blades and vanes are cooled so they can withstand these extreme temperatures. Film cooling is a cooling technique widely used in high-performance gas turbines. However, the film cooling effectiveness has almost reached plateau, resulting in a bottleneck for continuous improvement of gas turbines' efficiency.

In this study, an innovative cooling scheme, mist film cooling is investigated through experiments. A small amount of tiny water droplets with an average diameter about 10-15 …

Numerical Modelling Of Downburst Interaction With Bluff Body, Aditi Jog

Electronic Thesis and Dissertation Repository

The objective of this study is to investigate the interaction of a bluff body with a downburst flow. Numerical investigation of the flow field using CFD analysis was carried out for three different downburst sizes (h/d=1, 2, 4) under suitable boundary conditions subjected to constant jet velocity. The downburst-structure interaction study was conducted for two jet diameters (h/d=1 and 4) and two radial locations from the downburst center.

The results showed that the downburst size greatly dominates the intensity of the flow. The largest downburst resulted in the highest velocity magnitude near the ground and also covered a larger area …

Adsorption And Diffusion Of Gases In Nano-Porous Materials, Nethika Sahani Suraweera

Doctoral Dissertations

In this work, a systematic computational study directed toward developing a molecular-level understanding of gas adsorption and diffusion characteristics in nano-porous materials is presented. Two different types of porous adsorbents were studied, one crystalline and the other amorphous. Physisorption and diffusion of hydrogen in ten iso-reticular metal-organic frameworks (IRMOFs) were investigated. A set of nine adsorbents taken from a class of novel, amorphous nano-porous materials composed of spherosilicate building blocks and isolated metal sites was also studied, with attention paid to the adsorptive and diffusive behavior of hydrogen, methane, carbon dioxide and their binary mixtures. Both classes of materials were …

Effects Of Data Resolution And Human Behavior On Large Scale Evacuation Simulations, Wei Lu

Doctoral Dissertations

Traffic Analysis Zones (TAZ) based macroscopic simulation studies are mostly applied in evacuation planning and operation areas. The large size in TAZ and aggregated information of macroscopic simulation underestimate the real evacuation performance. To take advantage of the high resolution demographic data LandScan USA (the zone size is much smaller than TAZ) and agent-based microscopic traffic simulation models, many new problems appeared and novel solutions are needed. A series of studies are conducted using LandScan USA Population Cells (LPC) data for evacuation assignments with different network configurations, travel demand models, and travelers’ compliance behavior.

First, a new Multiple-Source-Nearest-Destination Shortest Path …

Bayesian Dictionary Learning For Single And Coupled Feature Spaces, Li He

Doctoral Dissertations

Over-complete bases offer the flexibility to represent much wider range of signals with more elementary basis atoms than signal dimension. The use of over-complete dictionaries for sparse representation has been a new trend recently and has increasingly become recognized as providing high performance for applications such as denoise, image super-resolution, inpaiting, compression, blind source separation and linear unmixing. This dissertation studies the dictionary learning for single or coupled feature spaces and its application in image restoration tasks. A Bayesian strategy using a beta process prior is applied to solve both problems.

Firstly, we illustrate how to generalize the existing beta …

Extension Of A High-Order Petrov-Galerkin Implementation Applied To Non-Radiating And Radar Cross Section Geometries, William L. Shoemake

Masters Theses and Doctoral Dissertations

Capabilities of a high-order Petrov-Galerkin solver are expanded to include N-port systems. Tait-Bryan angles are employed to launch electro-magnetic waves in arbitrary directions allowing off axis ports to be driven. The transverse-electric (TE) formulation is added allowing waveguide geometries to be driven directly. A grid convergence study is performed on a coax-driven waveguide system. Physical data are matched to a hybrid-T junction (magic-T) electromagnetic waveguide structure to verify the TE driving formulation along with the Tait-Bryan angles and modified post-processing routines. A simple sphere case is used to exercise the radar cross section (RCS) routines and to examine the benefits …

Stabilized Finite Elements For Compressible Turbulent Navier-Stokes, Jon Taylor Erwin

Masters Theses and Doctoral Dissertations

In this research a stabilized finite element approach is utilized in the development of a high-order flow solver for compressible turbulent flows. The Reynolds averaged Navier-Stokes (RANS) equations and modified Spalart-Almaras (SA) turbulence model are discretized using the streamline/upwind Petrov-Galerkin (SUPG) scheme. A fully implicit methodology is used to obtain steady state solutions or to drive unsteady problems at each time step. Order of accuracy is assessed for inviscid and viscous flows in two and three dimensions via the method of manufactured solutions. Proper treatment of curved surface geometries is of vital importance in high-order methods, especially when high aspect …

Higher-Order Petrov-Galerkin Methods For Analysis Of Antennas, Xueying Zhang

Masters Theses and Doctoral Dissertations

A temporally and spatially high-order accurate Petrov-Galerkin finite-element method is applied to the analysis of several antenna configurations. The method obtains numerical solutions of Maxwell's equations in the time domain using implicit time stepping and introduces energy into the domain using a Gaussian pulse to allow frequency-domain parameters to be computed over a range of frequencies with a single time-dependent solution. Verification cases for a monopole antenna and a microstrip patch antenna are used to examine the accuracy of the algorithm. Effects of varying antenna parameters on subsequent performance metrics are discussed based on the results from the simulations. Post-processing …

A New Software Framework For Unstructured Mesh Representation And Manipulation, Craig R. Tanis

Masters Theses and Doctoral Dissertations

This research presents a unique new software framework for representing and manipulating unstructured meshes in parallel, for use in modern scientific simulation codes. Due to the central nature of the unstructured mesh, this framework provides a variety of functionality, desirable throughout the lifecycle of an application, such as IO, parallel partitioning, phantom node data updates, adaptive refinement, derefinement and load balancing. What makes the framework unique is a focus on generality: like a database, the user provides a programmatic schema defining the structure of the mesh, including topological descriptions of the valid mesh entities. The system extracts adjacency information from …

Validation Of Interpolative Interfaces For Rotorcraft Applications, Adam L. Cofer

Masters Theses and Doctoral Dissertations

The study uses computational methods to simulate fluid flow on the NASA ROBIN helicopter model and on a simplified rotor geometry previously tested at Mississippi State. The ROBIN model and the rotor are run using an unstructured grid. Results from the Tenasi flow solver are compared against both simulated and wind tunnel data. Tenasi is an unstructured, Reynolds Averaged Navier-Stokes (RANS) solver developed at the SimCenter: National Center for Computational Engineering, located at the University of Tennessee at Chattanooga. Steady-state results for the isolated ROBIN fuselage and unsteady results for both fuselage and rotor systems are computed. In the unsteady …

2-D Cfd Design Of The Cross-Sectional Shape Of Arterial Stents, Kristen Karman

Masters Theses and Doctoral Dissertations

An approach for desigining arterial stents to maximize wall shear stress is presented. A cost equation to maximize wall shear stress is derived and then inverted into a minimization problem for the optimizer. A 2-D mixed-element finite-volume scheme for solving the compressible Navier-Stokes equations is implemented. A paramaterization of the cross- sectional shape of the stent wire using Hicks-Henne functions is described. The strategies used in the commercial optimization software, DAKOTA, to minimize the cost equation are described. The solver is validated using well known fluid flow test cases and is shown to match other published computed results for bloodflow …

Physics-Based Point Placement By Particle Dynamics Simulation, Philip Wesley Fackler

Masters Theses and Doctoral Dissertations

A physics-based approach to point cloud distribution for mesh generation is investigated using inter-nodal attraction and repulsion forces based on the Lennard-Jones pair potential and a simplified particle dynamics simulation. This method produces smooth distributions of points which accurately correspond to desired scalar spacing fields. Resulting point distributions are triangulated using Lawson's algorithm and the quality of these resulting meshes is measured, demonstrating the effectiveness of the approach. Several features planned for future development for increasing the robustness and versatility of the proposed method are discussed.

Action Potential Simulation Of The Hirudo Medicinalis's Retzius Cell In Matlab, Zechari Ryan Tempesta

Master's Theses

Modification of Hodgkin and Huxley’s experimentally derived set of nonlinear differential equations was implemented to accurately simulate the action potential of the Hirudo Medicinalis’s Retzius cell in MATLAB under analogous conditions to those found in the Retzius cell environment. The voltage-gated sodium and potassium channel responses to changes in membrane potential, as experimentally determined by Hodgkin and Huxley, were manipulated to suit simulation parameters established by electrophysiological Retzius cell recordings. Application of this methodology permitted additional accurate simulation of the Hirudo Medicinalis’s P cell under analogous conditions to those found in the P cell environment. Further refinement of this technique …

Artist-Driven Fracturing Of Polyhedral Surface Meshes, Tyler Casella

Master's Theses

This paper presents a robust and artist driven method for fracturing a surface polyhedral mesh via fracture maps. A fracture map is an undirected simple graph with nodes representing positions in UV-space and fracture lines along the surface of a mesh. Fracture maps allow artists to concisely and rapidly define, edit, and apply fracture patterns onto the surface of their mesh.

The method projects a fracture map onto a polyhedral surface and splits its triangles accordingly. The polyhedral mesh is then segmented based on fracture lines to produce a set of independent surfaces called fracture components, containing the visible surface …

Using Real Property Layouts To Study The Foreclosure Contagion Effect In Real Estate With Agent-Based Modeling And Simulation, Daniele Vernon-Bido

Computational Modeling & Simulation Engineering Theses & Dissertations

Foreclosures in the United States increased sharply from 2007 to 2009. These foreclosures had a spillover effect on neighboring property values causing additional foreclosures. This is known as the foreclosure contagion effect.

Recent studies have quantified the discount attributed to foreclosure contagion using equation-based techniques. However, the discount varied between studies and markets. Further studies using agent-based modeling and simulation have demonstrated the relationship between the discounts, the time a foreclosure remains on the market, the prevailing interest rates and the average property values.

This study uses agent-based modeling and simulation (ABMS) to explore the differences that varying neighborhood densities …

Essentially Analytical Theory Closure For Space Filtered Thermal-Incompressible Navier-Stokes Partial Differential Equation System On Bounded Domains, Mikhail Alexandrovich Sekachev

Doctoral Dissertations

Numerical simulation of turbulent flows is identified as one of the grand challenges in high-performance computing. The straight forward approach of solving the Navier-Stokes (NS) equations is termed Direct Numerical Simulation (DNS). In DNS the majority of computational effort is spent on resolving the smallest scales of turbulence, which makes this approach impractical for most industrial applications even on present-day supercomputers. A more feasible approach termed Large Eddy Simulation (LES) has evolved over the last five decades to facilitate turbulent flow predictions for reasonable Reynolds (Re) numbers and domain sizes. LES theory uses the concept of convolution with a spatial …

Network Dynamics Of Visual Naming, Christopher R. Conner

Dissertations & Theses (Open Access)

Recognition and naming of objects and actions are fundamental components of language. They involve several different systems working in coordination to accomplish a complex behavior. During visual naming, sensory and semantic processing are carried out by dedicated cortical substrates in the temporal and occipital lobes, while response selection and articulatory planning are handled by prefrontal cortex. Despite decades of research using lesion analysis, functional MRI and electro-encephalography, the precise dynamics involved remain unknown due to the inadequate spatio-temporal resolution of these methodologies. Of particular interest is the organization of semantic knowledge and the degree of serial and parallel organization of …

Preconditioning Methods For Ideal And Multiphase Fluid Flows, Ashish Gupta

Masters Theses and Doctoral Dissertations

The objective of this study is to develop a preconditioning method for ideal and multiphase multispecies compressible fluid flow solver using homogeneous equilibrium mixture model. The mathematical model for fluid flow going through phase change uses density and temperature in the formulation, where the density represents the multiphase mixture density. The change of phase of the fluid is then explicitly determined using the equation of state of the fluid, which only requires temperature and mixture density. The method developed is based on a finite-volume framework in which the numerical fluxes are computed using Roe’s [1] approximate Riemann solver and the …

Computational Investigation Of The Effects Of Casing Treatments On The Performance Of A Turbofan, Weiyang Lin

Masters Theses and Doctoral Dissertations

A computational survey focused on modifications to the casing near the rotor blade tip is carried out for the purpose of enhancing the performance and increasing the stall margin of a model turbofan stage in transonic operating conditions. The study is divided into three phases. During the first phase two types of casing treatments, inward protruding rings and circumferential grooves, were tested with relatively coarse grids. In the second phase, a grid resolution study is carried out with the results from this phase influencing the choices for the third stage. In the third phase, a comprehensive study is performed to …

Computing Radiation Exchange, Jonathan L. Nutzati Fontaine

Doctoral Dissertations and Master's Theses

A computational tool to simulate thermal radiation between surfaces is developed. The output is verified against cases for which the analytical solutions are available. The tool can be used as a stand-alone program, or as an interactive module for CFD. In such an application the module would augment other heat transfer boundary conditions. The tool is demonstrated by post-processing surface temperature field data from a supersonic CFD calculation. The result is a net thermal radiation surface data field - the black body radiative effluxes as functions of temperature, less the integrated influxes multiplied by their geometric view factors from other …

A Multi-Configuration Display Methodology Incorporating Reflection For Real-Time Haptic-Interactive Virtual Environments, Mohammad F. Obeid

Computational Modeling & Simulation Engineering Theses & Dissertations

There is a natural need for real-time min-or reflection in many interactive virtual reality applications to achieve visuo-haptic collocation through optical reflection. Its use, however, calls for adjustments to the original model since a mirror reverses image characteristics. This thesis introduces a design and implementation of a generic configuration component for virtual environments that adjusts image characteristics and haptic interfaces to accommodate various display setups while preserving the correct orientation and properties of the original models in the graphical scene. Four different but related approaches were developed for image connection and are compared and contrasted against primary criteria. The haptic …

0tter - 0g Tracking And Targeting Experiment In Real-Time, Brandon Bussjaeger

Computer Science and Software Engineering

No abstract provided.

Point Based Approximate Color Bleeding With Cuda, Nicholas D. Feeney

Master's Theses

Simulating light is a very computationally expensive proposition. There are a wide variety of global illumination algorithms that are implemented and used by major motion picture companies to render interesting and believable scenes. Every algorithm strives to find a balance between speed and accuracy. The Point Based Approximate Color Bleeding algorithm is one of the most widely used algorithms in the field today. The Point Based Approximate Color Bleeding(PBACB) global illumination algorithm is based on the central idea that the geometry and direct illumination of the scene can be approximated by using a point cloud representation. This point cloud representation …

Paris: A Parallel Rsa-Prime Inspection Tool, Joseph R. White

Master's Theses

Modern-day computer security relies heavily on cryptography as a means to protect the data that we have become increasingly reliant on. As the Internet becomes more ubiquitous, methods of security must be better than ever. Validation tools can be leveraged to help increase our confidence and accountability for methods we employ to secure our systems.

Security validation, however, can be difficult and time-consuming. As our computational ability increases, calculations that were once considered “hard” due to length of computation, can now be done in minutes. We are constantly increasing the size of our keys and attempting to make computations harder …

Algorithms For Library-Based Microbial Source Tracking, Aldrin Montana

Master's Theses

Pyroprinting is a novel, library-based microbial source tracking method developed by the Biology department at Cal Poly, San Luis Obispo. This method consists of two parts: (1) a collection of bacterial fingerprints, called pyroprints, from known host species, and (2) a method for pyroprint comparison. Currently, Cal Poly Library of Pyroprints (CPLOP), a web-based database application, provides storage and analysis of over $10000$ pyroprints. This number is quickly growing as students and researchers continue to use pyroprinting for research. Biologists conducting research using pyroprinting rely on methods for partitioning collected bacterial isolates into bacterial strains. Clustering algorithms are commonly used …

Computation Of Heat Transfer In Turbine Rotor Blade Cooling Channels With Angled Rib Turbulators, Guy Austin Flynt

Masters Theses and Doctoral Dissertations

The effects of rotation and Reynolds number on heat transfer in rotating two-pass square and rectangular channels with smooth walls and walls with 45 degree angled and V-shaped rib turbulators were investigated numerically using an unstructured, incompressible, Reynolds-averaged Navier-Stokes flow solver. The influence of 45 degree angled ribs and channel orientation on the local Nusselt number ratios for leading and trailing surfaces in a two-pass square channel (AR=1) are compared to experimental data for Reynolds numbers from 5,000 to 25,000 and dimensionless rotation numbers from 0.0 to 0.118. The influence of V-shaped ribs and channel orientation on the local Nusselt …

A Survey Of Systems For Predicting Stock Market Movements, Combining Market Indicators And Machine Learning Classifiers, Jeffrey Allan Caley

Dissertations and Theses

In this work, we propose and investigate a series of methods to predict stock market movements. These methods use stock market technical and macroeconomic indicators as inputs into different machine learning classifiers. The objective is to survey existing domain knowledge, and combine multiple techniques into one method to predict daily market movements for stocks. Approaches using nearest neighbor classification, support vector machine classification, K-means classification, principal component analysis and genetic algorithms for feature reduction and redefining the classification rule were explored. Ten stocks, 9 companies and 1 index, were used to evaluate each iteration of the trading method. The classification …

Computational Material Modeling For Mechanical Properties Prediction And A Methodology For Mie Gruneisen Equation Of State Characterization Via Molecular/Nano Scale Cementitious Material Constituents, Ahmed Mohamed

Dissertations

Cementitious materials have complex hierarchical structures with random features that range from nanometer (nm) to millimeter (mm) scale. Processes occurring at the nanometer scale affect the performance at larger length scales. The present work employs molecular dynamics (MD) simulations as the computational modeling methodology to predict mechanical properties for both hydrated and unhydrated cementitious materials at the molecular/nano scale level. A detailed study on the effect of increasing MD simulation cell size, dynamics time duration on the predicted mechanical properties was performed. Further studies focused on understanding the effect of higher thermodynamic pressure states on predicted …

Two-Dimensional Hydrodynamic Modeling Of Two-Phase Flow For Understanding Geyser Phenomena In Urban Stormwater System, Zhiyu S. Shao

Theses and Dissertations--Civil Engineering

During intense rain events a stormwater system can fill rapidly and undergo a transition from open channel flow to pressurized flow. This transition can create large discrete pockets of trapped air in the system. These pockets are pressurized in the horizontal reaches of the system and then are released through vertical vents. In extreme cases, the transition and release of air pockets can create a geyser feature.

The current models are inadequate for simulating mixed flows with complicated air-water interactions, such as geysers. Additionally, the simulation of air escaping in the vertical dropshaft is greatly simplified, or completely ignored, in …

Architecture--Performance Interrelationship Analysis In Single/Multiple Cpu/Gpu Computing Systems: Application To Composite Process Flow Modeling, Richard Harrison Haney

Dissertations

Current developments in computing have shown the advantage of using one or more Graphic Processing Units (GPU) to boost the performance of many computationally intensive applications but there are still limits to these GPU-enhanced systems. The major factors that contribute to the limitations of GPU(s) for High Performance Computing (HPC) can be categorized as hardware and software oriented in nature. Understanding how these factors affect performance is essential to develop efficient and robust applications codes that employ one or more GPU devices as powerful co-processors for HPC computational modeling. The present work analyzes and understands the intrinsic interrelationship of both …