A systematic approach for integrated product, materials, and design-process design

Designers are challenged to manage customer, technology, and socio-economic uncertainty causing dynamic, unquenchable demands on limited resources. In this context, increased concept flexibility, referring to a designer s ability to generate concepts, is crucial. Concept flexibility can be significantly increased through the integrated design of product and material concepts. Hence, the challenge is to leverage knowledge of material structure-property relations that significantly affect system concepts for function-based, systematic design of product and materials concepts in an integrated fashion. However, having selected an integrated product and material system concept, managing complexity in embodiment design-processes is important. Facing a complex network of decisions and evolving analysis models a designer needs the flexibility to systematically generate and evaluate embodiment design-process alternatives. In order to address these challenges and respond to the primary research question of how to increase a designer s concept and design-process flexibility to enhance product creation in the conceptual and early embodiment design phases, the primary hypothesis in this dissertation is embodied as a systematic approach for integrated product, materials and design-process design. The systematic approach consists of two components i) a function-based, systematic approach to the integrated design of product and material concepts from a systems perspective, and ii) a systematic strategy to design-process generation and selection based on a decision-centric perspective and a value-of-information-based Process Performance Indicator. The systematic approach is validated using the validation-square approach that consists of theoretical and empirical validation. Empirical validation of the framework is carried out using various examples including: i) design of a reactive material containment system, and ii) design of an optoelectronic communication system.Ph.D.Committee Chair: Allen, Janet K.; Committee Member: Aidun, Cyrus K.; Committee Member: Klein, Benjamin; Committee Member: McDowell, David L.; Committee Member: Mistree, Farrokh; Committee Member: Yoder, Douglas P

Simulation of the Spherically Symmetric Stellar Core Collapse, Bounce, and Postbounce Evolution of a 13 Solar Mass Star with Boltzmann Neutrino Transport, and Its Implications for the Supernova Mechanism

With exact three-flavor Boltzmann neutrino transport, we simulate the stellar core collapse, bounce, and postbounce evolution of a 13 solar mass star in spherical symmetry, the Newtonian limit, without invoking convection. In the absence of convection, prior spherically symmetric models, which implemented approximations to Boltzmann transport, failed to produce explosions. We are motivated to consider exact transport to determine if these failures were due to the transport approximations made and to answer remaining fundamental questions in supernova theory. The model presented here is the first in a sequence of models beginning with different progenitors. In this model, a supernova explosion is not obtained. We discuss the ramifications of our results for the supernova mechanism.Comment: 5 pages, 3 figures, Submitted to Physical Review Letter

General Relativistic Simulations of Stellar Core Collapse and Postbounce Evolution with Boltzmann Neutrino Transport

We present self-consistent general relativistic simulations of stellar core collapse, bounce, and postbounce evolution for 13, 15, and 20 solar mass progenitors in spherical symmetry. Our simulations implement three-flavor Boltzmann neutrino transport and standard nuclear physics. The results are compared to our corresponding simulations with Newtonian hydrodynamics and O(v/c) Boltzmann transport.Comment: 6 pages, 3 figures, to appear in Proceedings of the 20th Texas Symposium on Relativistic Astrophysics, edited by J.C. Wheeler and H. Martel (American Institute of Physics

A Finite Difference Representation of Neutrino Radiation Hydrodynamics in Spherically Symmetric General Relativistic Space-Time

We present an implicit finite difference representation for general relativistic radiation hydrodynamics in spherical symmetry. Our code, Agile-Boltztran, solves the Boltzmann transport equation for the angular and spectral neutrino distribution functions in self-consistent simulations of stellar core collapse and postbounce evolution. It implements a dynamically adaptive grid in comoving coordinates. Most macroscopically interesting physical quantities are defined by expectation values of the distribution function. We optimize the finite differencing of the microscopic transport equation for a consistent evolution of important expectation values. We test our code in simulations launched from progenitor stars with 13 solar masses and 40 solar masses. ~0.5 s after core collapse and bounce, the protoneutron star in the latter case reaches its maximum mass and collapses further to form a black hole. When the hydrostatic gravitational contraction sets in, we find a transient increase in electron flavor neutrino luminosities due to a change in the accretion rate. The muon- and tauon-neutrino luminosities and rms energies, however, continue to rise because previously shock-heated material with a non-degenerate electron gas starts to replace the cool degenerate material at their production site. We demonstrate this by supplementing the concept of neutrinospheres with a more detailed statistical description of the origin of escaping neutrinos. We compare the evolution of the 13 solar mass progenitor star to simulations with the MGFLD approximation, based on a recently developed flux limiter. We find similar results in the postbounce phase and validate this MGFLD approach for the spherically symmetric case with standard input physics.Comment: reformatted to 63 pages, 24 figures, to be published in ApJ

Global Comparison of Core-Collapse Supernova Simulations in Spherical Symmetry

We present a comparison between several simulation codes designed to study the core-collapse supernova mechanism. We pay close attention to controlling the initial conditions and input physics in order to ensure a meaningful and informative comparison. Our goal is three-fold. First, we aim to demonstrate the current level of agreement between various groups studying the core-collapse supernova central engine. Second, we desire to form a strong basis for future simulation codes and methods to compare to. Lastly, we want this work to be a stepping stone for future work exploring more complex simulations of core-collapse supernovae, i.e., simulations in multiple dimensions and simulations with modern neutrino and nuclear physics. We compare the early (first ~500ms after core bounce) spherically-symmetric evolution of a 20 solar mass progenitor star from six different core-collapse supernovae codes: 3DnSNe-IDSA, AGILE-BOLTZTRAN, FLASH, F{\sc{ornax}}, GR1D, and PROMETHEUS-VERTEX. Given the diversity of neutrino transport and hydrodynamic methods employed, we find excellent agreement in many critical quantities, including the shock radius evolution and the amount of neutrino heating. Our results provide an excellent starting point from which to extend this comparison to higher dimensions and compare the development of hydrodynamic instabilities that are crucial to the supernova explosion mechanism, such as turbulence and convection.Comment: 24 pages, 7 figures, J. Phys. G focus issue on core-collapse supernovae. This document was written collaboratively on Authorea, comments welcome at https://www.authorea.com/users/1943/articles/167397-global-comparison-of-core-collapse-supernova-simulations-in-spherical-symmetr

Pulsed ultrasonic doppler velocimetry for measurement of velocity profiles in small channels and capplilaries

Pulsed ultrasound Doppler velocimetry proved to be capable of measuring velocities accurately (relative error less than 0.5 percent). In this research, the limitations of the method are investigated when measuring: in channels with a small thickness compared to the transducer diameter, at low velocities and in the presence of a flow reversal area. A review of the fundamentals of pulsed ultrasound Doppler velocimetry reveals that the accuracy of the measured velocity field mainly depends on the shape of the acoustic beam through the flow field and the intensity of the echo from the incident particles where the velocity is being measured. The ultrasonic transducer turned out to be most critical component of the system. Fundamental limitations of the method are identified. With ultrasonic beam measurements, the beam shape and echo intensity is further investigated. In general, the shape of the ultrasonic beam varies depending on the frequency and diameter of the emitter as well as the characteristics of the acoustic interface that the beam encounters. Moreover, the most promising transducer to measure velocity profiles in small channels is identified. Since the application of pulsed ultrasound Doppler velocimetry often involves the propagation of the ultrasonic burst through Plexiglas, the effect of Plexiglas walls on the measured velocity profile is analyzed and quantified in detail. The transducers ringing effect and the saturation region caused by highly absorbing acoustic interfaces are identified as limitations of the method. By comparing measurement results in the small rectangular channel to numerically calculated results, further limitations of the method are identified. It was not possible to determine velocities correctly throughout the whole channel at low flow rates, in small geometries and in the flow separation region. A discrepancy between the maximum measured velocity, velocity profile perturbations and incorrect velocity determination at the far channel wall were main shortcomings. Measurement results are improved by changes in the Doppler angle, the flow rate and the particle concentration. Suggestions to enhance the measurement system, especially its spatial resolution, and to further investigate acoustic wave interactions are made.M.S.Committee Member: Cyrus K. Aidun; Committee Member: Farrokh Mistree; Committee Member: Philip J. W. Roberts; Committee Member: Yves H. Berthelo