Computational Engineering Commons^™

Development And Validation Of An Open-Source Qct-Based Finite Element Analysis And Phase Field Modeling For Fracture Prediction In Goat Tibia, Debangshu Paul

Masters Theses

Predicting mechanical responses under various load conditions is of significant interest in the field of orthopedic research. Despite an abundance of research on finite element (FE) modeling for human bones, studies specifically focusing on the tibia remain notably limited. Given that mechanical properties and structural form of goat tibiae closely mimic those of human tibiae at the region of interest (ROI), they can serve as excellent models for comparative orthopedic research. While existing literature on ovine bone research offers rich in-vivo models, it lacks a validated FE model of the tibia subjected to thorough spatial error assessment.

This thesis presents …

A Cfd Study On The Performance Of High Speed Planing Hulls, Mowgli J. Crosby

Masters Theses

Most high speed water craft are able to achieve high speeds through the use of a planing hull. Planing hulls use hydrodynamic forces to lift a portion of the vessel out of the water, reducing drag, and allowing for greater speeds. Determining the flow around such vessels is traditionally achieved using a scale model in a tow tank. The purpose of this study was to analyze the performance of a high speed planing hull determine the effects of several geometric features using computational fluid dynamics rather than traditional experimentation. The goal was to determine the best configuration to ensure the …

Mixed-Mode Dynamic Crack Propagation Using The Discontinuous Galerkin Method, Russell Thomas Hollman

Masters Theses

A recently proposed Discontinuous Galerkin (DG) method for modeling nonlinear fracture mechanics problems in the context of the finite element method is investigated. The DG method provides a framework for fracture mechanics by employing interface elements within the region of interest where cracking is expected. Previous studies have shown that the use of traction-separation laws within the DG method have enhanced stability for dynamic problems by removing the issue of artificial compliance compared to intrinsic cohesive zone elements. The purpose of this thesis is to apply the DG method to a mixed-mode dynamic crack propagation problem, namely the Kalthoff-Winkler experiment. …

Improving Ventricular Catheter Design Through Computational Fluid Dynamics, Sofy Hefets Weisenberg

Masters Theses

Cerebrospinal fluid (CSF) shunts are fully implantable medical devices that are used to treat patients suffering from conditions characterized by elevated intracranial pressure, such as hydrocephalus. In cases of shunt failure or malfunction, patients are often required to endure one or more revision surgeries to replace all or part of the shunt. One of the primary causes of CSF shunt failure is obstruction of the ventricular catheter, a component of the shunt system implanted directly into the brain's ventricular system. This work aims to improve the design of ventricular catheters in order to reduce the incidence of catheter obstruction and …

Control Of Cation Ordering In Zinc Tin Nitride And In-Situ Monitoring Of Growth, Brian Christopher Durant

Masters Theses

Semiconducting materials with a band gap around 1.5 eV are very much sought after due to their close match to the solar spectrum. However, some compounds that have shown promise for highly efficient solar cells contain rare, expensive, and sometimes toxic elements, such as indium and gallium. As such, a search for earth abundant materials has become more prominent recently. One such earth abundant semiconducting material that has garnered interest is ZnSnN₂. It has been shown through previous studies that there is the possibility of continuously tuning the band gap between 1.0 and 2.0 eV by controlling the …

From Mpi To Openshmem: Porting Lammps, Chunyan Tang

Masters Theses

This work details the opportunities and challenges of porting a petascale-capable, MPI-based application LAMMPS to OpenSHMEM. We investigate the major programming challenges stemming from the differences in communication semantics, address space organization, and synchronization operations between the two pro- gramming models. This work provides several approaches to solve those challenges for representative communication patterns in LAMMPS, e.g., by utilizing group synchronization, peer’s buffer status tracking, double buffer strategy and unpacked direct transfer of data. The performance of LAMMPS is evaluated on the Titan HPC system at ORNL. The OpenSHMEM implementations are compared with MPI version in terms of both strong …

Analytical And Computational Modeling Of Membrane Nanotubes, Sina Mirzaeifard

Masters Theses

This thesis investigates the interplay between cell membranes and the actin cytoskeleton in cellular structures known as membrane nanotubes. Membrane nanotubes are slender membrane structures that physically connect cells over long distances, and experiments suggest that they play a role in transferring material and information between cells. Disrupting the actin cytoskeleton disrupts membrane nanotubes. Although recent studies have revealed insight into the physical properties and functions of membrane-actin systems, further research is needed to understand their behavior in biological contexts. Membrane nanotubes provide a novel system with which to investigate interactions between the cell membrane and actin.

In this thesis, …

Real-Time Hybrid Simulation With Online Model Updating, Adam Mueller

Masters Theses

Hybrid simulations have shown great potential for economic and reliable assessment of structural seismic performance through a combination of physically tested components, called the experimental substructure, and numerically simulated components, called the numerical substructure. Current hybrid simulation practices often use a fixed numerical model without considering the possible availability of a more accurate model obtained during hybrid simulation through an online model updating technique. To address this limitation and improve the reliability of numerical models in hybrid simulations, this study describes the implementation of an online model updating method in real-time hybrid simulation (RTHS). The Unscented Kalman Filter (UKF) was …

Graphics Processing Unit Bloom Filters: Classical And Probabilistic, Joshua Michael Pyle

Masters Theses

Graphics Processing Units (GPUs) have been used to enhance the speed and efficiency of both data structures and algorithms alike. A common data structure used in Computer Science is the Bloom Filter, which is used in many types of applications including databases and security logging. The Bloom Filter is a lossy data structure that uses several hash functions to store keys into a bit array. A novel, new Bloom Filter meant for use in internet traffic detection called the Probabilistic Bloom Filter has recently been developed. In practice, this new Bloom Filter typically makes use of more hash functions than …

A Validation Study Of The Amp Nuclear Fuel Performance Code, Aaron Martin Phillippe

Masters Theses

The Advanced Multi-Physics (AMP) Fuel Performance Code is a fully coupled, 3-dimensional (3D) code currently in development at the Oak Ridge National Laboratory (ORNL) for the purposes of advanced fuel performance evaluation and simulation. The purpose of this study was to investigate and examine the capabilities of AMP, as developed so far, in thermo-mechanical evaluations of experimental benchmark data. The IFA-432 and IFA-597 datasets from the Nuclear Energy Agency’s (NEA) International Fuel Performance Experiments (IFPE) database were examined, and a code-to-code comparison made against FRAPCON-3.4, a one dimensional (1D) code used by the Nuclear Regulatory Commission (NRC) for fuel licensing. …

Development And Verification Of A Navier-Stokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell

Masters Theses

Vorticity Confinement (VC) is a numerical technique which enhances computation of fluid flows by acting as negative diffusion within the limit of vortical regions, preventing the inherent numerical dissipation present with conventional methods. VC shares similarities with large eddy simulation (LES), but its behavior is based on a stable negative dissipation of vortical structures controlled by the automatic balance between two parameters, μ [mu] and ε [epsilon].

In this thesis, three-dimensional, parallel-computing Navier-Stokes solvers with VC are developed using the OpenFOAM computational framework. OpenFOAM is an open-source collection of C++ libraries developed for computational fluid dynamics. Object-oriented programming concepts are …

Propagation Of Periodic Waves Using Wave Confinement, Paula Cysneiros Sanematsu

Masters Theses

This thesis studies the behavior of the Eulerian scheme, with "Wave Confinement" (WC), when propagating periodic waves. WC is a recently developed method that was derived from the scheme "vorticity confinement" used in fluid mechanics, and it efficiently solves the linear wave equation. This new method is applicable for numerous simulations such as radio wave propagation, target detection, cell phone and satellite communications.

The WC scheme adds a nonlinear term to the discrete wave equation that adds stability with negative and positive diffusion, conserves integral quantities such as total amplitude and wave speed, and it allows wave propagation over long …