ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Displaying 1 - 2 of 2
Filtering by
- All Subjects: Computational Physics
Description
This thesis focuses on studying the interaction between floating objects and an air-water flow system driven by gravity. The system consists of an inclined channel in which a gravity driven two phase flow carries a series of floating solid objects downstream. Numerical simulations of such a system requires the solution of not only the basic Navier-Stokes equation but also dynamic interaction between the solid body and the two-phase flow. In particular, this requires embedding of dynamic mesh within the two-phase flow. A computational fluid dynamics solver, ANSYS fluent, is used to solve this problem. Also, the individual components for these simulations are already available in the solver, few examples exist in which all are combined. A series of simulations are performed by varying the key parameters, including density of floating objects and mass flow rate at the inlet. The motion of the floating objects in those simulations are analyzed to determine the stability of the coupled flow-solid system. The simulations are successfully performed over a broad range of parametric values. The numerical framework developed in this study can potentially be used in applications, especially in assisting the design of similar gravity driven systems for transportation in manufacturing processes. In a small number of the simulations, two kinds of numerically instability are observed. One is characterized by a sudden vertical acceleration of the floating object due to a strong imbalance of the force acting on the body, which occurs when the mass flow of water is weak. The other is characterized by a sudden vertical movement of air-water interface, which occurs when two floating objects become too close together. These new types of numerical instability deserve future studies and clarifications. This study is performed only for a 2-D system. Extension of the numerical framework to a full 3-D setting is recommended as future work.
ContributorsMangavelli, Sai Chaitanya (Author) / Huang, Huei-Ping (Thesis advisor) / Kim, Jeonglae (Committee member) / Forzani, Erica (Committee member) / Arizona State University (Publisher)
Created2018
Description
Autonomic closure is a recently-proposed subgrid closure methodology for large eddy simulation (LES) that replaces the prescribed subgrid models used in traditional LES closure with highly generalized representations of subgrid terms and solution of a local system identification problem that allows the simulation itself to determine the local relation between each subgrid term and the resolved variables at every point and time. The present study demonstrates, for the first time, practical LES based on fully dynamic implementation of autonomic closure for the subgrid stress and the subgrid scalar flux. It leverages the inherent computational efficiency of tensorally-correct generalized representations in terms of parametric quantities, and uses the fundamental representation theory of Smith (1971) to develop complete and minimal tensorally-correct representations for the subgrid stress and scalar flux. It then assesses the accuracy of these representations via a priori tests, and compares with the corresponding accuracy from nonparametric representations and from traditional prescribed subgrid models. It then assesses the computational stability of autonomic closure with these tensorally-correct parametric representations, via forward simulations with a high-order pseudo-spectral code, including the extent to which any added stabilization is needed to ensure computational stability, and compares with the added stabilization needed in traditional closure with prescribed subgrid models. Further, it conducts a posteriori tests based on forward simulations of turbulent conserved scalar mixing with the same pseudo-spectral code, in which velocity and scalar statistics from autonomic closure with these representations are compared with corresponding statistics from traditional closure using prescribed models, and with corresponding statistics of filtered fields from direct numerical simulation (DNS). These comparisons show substantially greater accuracy from autonomic closure than from traditional closure. This study demonstrates that fully dynamic autonomic closure is a practical approach for LES that requires accuracy even at the smallest resolved scales.
ContributorsStallcup, Eric Warren (Author) / Dahm, Werner J.A. (Thesis advisor) / Herrmann, Marcus (Committee member) / Calhoun, Ronald (Committee member) / Kim, Jeonglae (Committee member) / Kostelich, Eric J. (Committee member) / Arizona State University (Publisher)
Created2020