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Interaction and Multiscale Mechanics
  Volume 3, Number 3, September 2010, pages 235-255
DOI: http://dx.doi.org/10.12989/imm.2010.3.3.235
 
open access

Investigation of allowable time-step sizes for generalized finite element analysis of the transient heat equation
P. O\'Hara, C.A. Duarte and T. Eason

 
Abstract
    This paper investigates the heat equation for domains subjected to an internal source with a sharp spatial gradient. The solution is first approximated using linear finite elements, and sufficiently small time-step sizes to yield stable simulations. The main area of interest is then in the ability to approximate the solution using Generalized Finite Elements, and again explore the time-step limitations required for stable simulations. Both high order elements, as well as elements with special enrichments are used to generate solutions. When compared to linear finite elements, the high order elements deliver better accuracy at a given level of mesh refinement, but do not offer an increase in critical time-step size. When special enrichment functions are used, the solution can be approximated accurately on very coarse meshes, while yielding solutions which are both accurate and computationally efficient. The major conclusion of interest is that the significantly larger element size yields larger allowable time-step sizes while still maintaining stability of the time-stepping algorithm.
 
Key Words
    generalized FEM; extended FEM; partition of unity methods; multi-scale methods; explicit time-stepping; critical time-step sizes.
 
Address
P. O\'Hara and C.A. Duarte: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Newmark Laboratory, 205 North Mathews Avenue, Urbana, Illinois 61801, USA
T. Eason: Air Force Research Laboratory, Air Vehicles Directorate, WPAFB, Ohio, USA
 

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