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

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.
Authors:
;
Publication Date:
OSTI Identifier:
752074
Report Number(s):
SAND2000-0608J
TRN: AH200017%%112
DOE Contract Number:
AC04-94AL85000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Water Resources Research; Other Information: Submitted to Water Resources Research; PBD: 8 Mar 2000
Research Org:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org:
US Department of Energy (US)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ENVIRONMENTAL TRANSPORT; MATHEMATICAL MODELS; DATA COVARIANCES; HYDRAULIC CONDUCTIVITY