On the continuum-scale simulation of gravity-driven fingers with hysteretic Richards equation: Trucation error induced numerical artifacts

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The authors consider the ability of the numerical solution of Richards equation to model gravity-driven fingers. Although gravity-driven fingers can be easily simulated using a partial downwind averaging method, they find the fingers are purely artificial, generated by the combined effects of truncation error induced oscillations and capillary hysteresis. Since Richards equation can only yield a monotonic solution for standard constitutive relations and constant flux boundary conditions, it is not the valid governing equation to model gravity-driven fingers, and therefore is also suspect for unsaturated flow in initially dry, highly nonlinear, and hysteretic media where these fingers occur. However, analysis ... continued below

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29 p.

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ELIASSI,MEHDI & GLASS JR.,ROBERT J. March 8, 2000.

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This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this article can be viewed below.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

The authors consider the ability of the numerical solution of Richards equation to model gravity-driven fingers. Although gravity-driven fingers can be easily simulated using a partial downwind averaging method, they find the fingers are purely artificial, generated by the combined effects of truncation error induced oscillations and capillary hysteresis. Since Richards equation can only yield a monotonic solution for standard constitutive relations and constant flux boundary conditions, it is not the valid governing equation to model gravity-driven fingers, and therefore is also suspect for unsaturated flow in initially dry, highly nonlinear, and hysteretic media where these fingers occur. However, analysis of truncation error at the wetting front for the partial downwind method suggests the required mathematical behavior of a more comprehensive and physically based modeling approach for this region of parameter space.

Physical Description

29 p.

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OSTI as DE00752074

Medium: P; Size: 29 pages

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  • Journal Name: Water Resources Research; Other Information: Submitted to Water Resources Research

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  • Report No.: SAND2000-0608J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 752074
  • Archival Resource Key: ark:/67531/metadc710449

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  • March 8, 2000

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  • Sept. 12, 2015, 6:31 a.m.

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  • April 10, 2017, 7:08 p.m.

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ELIASSI,MEHDI & GLASS JR.,ROBERT J. On the continuum-scale simulation of gravity-driven fingers with hysteretic Richards equation: Trucation error induced numerical artifacts, article, March 8, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc710449/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.