Dissertation/Thesis Abstract

An optimization-based method for high order gradient calculation on unstructured meshes
by Busatto, Alcides Dallanora, Ph.D., Mississippi State University, 2012, 150; 3522192
Abstract (Summary)

A new implicit and compact optimization-based method is presented for high order derivative calculation for finite-volume numerical method on unstructured meshes. High-order approaches to gradient calculation are often based on variants of the Least-Squares (L-S) method, an explicit method that requires a stencil large enough to accommodate the necessary variable information to calculate the derivatives. The new scheme proposed here is applicable for an arbitrary order of accuracy (demonstrated here up to 3rd order), and uses just the first level of face neighbors to compute all derivatives, thus reducing stencil size and avoiding stiffness in the calculation matrix.

Preliminary results for a static variable field example and solution of a simple scalar transport (advection) equation show that the proposed method is able to deliver numerical accuracy equivalent to (or better than) the nominal order of accuracy for both 2nd and 3rd order schemes in the presence of a smoothly distributed variable field (i.e., in the absence of discontinuities).

This new Optimization-based Gradient REconstruction (herein denoted OGRE) scheme produces, for the simple scalar transport test case, lower error and demands less computational time (for a given level of required precision) for a 3rd order scheme when compared to an equivalent L-S approach on a two-dimensional framework. For three-dimensional simulations, where the L-S scheme fails to obtain convergence without the help of limiters, the new scheme obtains stable convergence and also produces lower error solution when compared to a third order MUSCL scheme.

Furthermore, spectral analysis of results from the advection equation shows that the new scheme is better able to accurately resolve high wave number modes, which demonstrates its potential to better solve problems presenting a wide spectrum of wavelengths, for example unsteady turbulent flow simulations.

Indexing (document details)
Advisor: Walters, Dibbon K.
Commitee: Janus, Jonathan M., Kim, Seongjai, Luke, Edward A.
School: Mississippi State University
Department: Computational Engineering
School Location: United States -- Mississippi
Source: DAI-B 74/01(E), Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Applied Mathematics, Aerospace engineering, Electrical engineering
Keywords: Finite volume method, Gradient reconstruction, High order schemes, Unstructured meshes
Publication Number: 3522192
ISBN: 9781267540966
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