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One Team: Relevant . . . Ready . . . Responsive . . . Reliable

Basic Research Program

Particle-Scale Distribution of Soil Moisture in Porous Media

20 September 2007

Dr. Chris Kees and Dr. Matthew FarthingCoastal and Hydraulics Laboratory

Purpose: To develop a multi-scale theoretical and

computational model of variably saturated granular/porous media that will improve our ability to perform engineering-scale analyses.

Results:Theoretical and computational frameworks for

passing information between microscopic two-phase flow/particle systems to macroscopic variably saturated media.

New constitutive models for macroscopic models and numerical multiscale models for macroscale engineering models.

Payoff:Understanding the macroscopic structural,

hydraulic, thermal, electromagnetic, and chemical properties of variably saturated soils will lead to improved ability to detect subsurface targets and features, to build structures, and to predict chemical species transport in soils

Schedule & Cost

Total$ 726K

MILESTONES Prior FY07 FY08 FY09Years

Army 227 249 250Other

Initial Plan/Prep

($K)

Particle Scale Theory Particle Scale SimulatorThree-phase Theory

Particle-Scale Distribution of Soil Moisture in Porous Materials

Status:Basic 6.1

Particle-Scale Velocity and Pressure Computations

Three-phase Simulator

$726KTotal Army

Program

Multiscale TheoryMultiscale Simulator

What is the Problem? – We don’t understand the macroscopic structural, hydraulic, thermal, electromagnetic, and chemical properties of variably saturated soils. These properties affect our ability to detect subsurface targets and features, build structures, and predict chemical species transport in soils.

What are the barriers to solving the problem? – Accurately measuring thermodynamic conjugate variables in physical experiments under dynamic conditions, as required for formulation of fundamentally sound constitutive relationships, is not possible. Quantities such as phase pressures, surface tension, fluid phase distribution, fluid phase kinetic and potential energies cannot be independently measured at the pore scale.

Collaboration across ERDC, commercial firms and/or academia –

Ernest Berney (GSL) - Physics of granular mediaClint Willson (LSU), - Particle scale measurementsTim Kelley (NCSU) - Multilevel solvers analysisClint Dawson(UT, Austin) – Finite element analysisHigh Fidelity Vessel Effects Project (CHL) Countermine phenomenology (GSL) Institute for Maneuverability and Terrain Physics (ITL)

What is innovative about this work? The use of particle-scale continuum fluid mechanics simulations that explicitly model the separate phases and the fluid-water and fluid-solid interfaces. The coupling of those models to discrete element models of granular materials to facilitate multi-scale numerical modeling of these systems.

What is your publication plan? FY07 - Mini-symposium on near surface air/water flow at U.S.

National Congress on Computational Mechanics (July). FY08 - Advances in Water Resources FY09 - Journal of Computational Physics, Multiscale Modeling

and Simulation (SIAM).

Particle-Scale Distribution of Soil Moisture in Porous Materials

How will you overcome these barriers? – Apply state-of-the-art computational methods to rigorous continuum thermo-mechanical models of the interaction of air and water phases in granular materials; collaborate with experimentalists and numerical analysis specialists from academia.

What are the results of this research and what is its value? – A multiscale theoretical and computational modeling capability for variably saturated granular materials. The ability to calculate macroscopic properties from particle-scale measurements and/or use simulations to supplement experimental methods in complex three-dimensional settings where direct observation of all physical quantities is not possible; a computational multiscale framework that can be used to carry out fundamentally sound engineering analyses.


Accomplishments / Status• Working prototype of 2D/3D air/water

Navier-Stokes model based on front-capturing approaches.

• Working prototypes of 1D/2D/3D macro-scale (porous media) air/water flow models using locally mass-conservative continuous and discontinuous finite element methods.

• Set up five month visit to UT by Kees to collaborate with various researchers on numerical and pore-/multi-scale modeling issues.


Accomplishments / Status

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Accomplishments / Status

Cross-section of a 3D tomographic image showingresidual water (blue), air (red), sand (green). Courtesy of Clint Willson, LSU.


• Theoretical and computational frameworks for passing information between microscopic two-phase flow/particle systems to macroscopic variably saturated media.

• New constitutive models for macroscopic models and numerical multiscale models for macroscale engineering models.

Products


• High-fidelity vessel effects(Kees and Farthing): Arbitrary Lagrangian-Eulerian mesh technology and porous structure theory/models.

• Countermine Phenomenology(Howington): Mesh generation capability and moisture distribution theory/models.

• Stress Transfer in Granular Media(Peters):Discrete Element method coupling and upscaling tools, surface tension theory/models.

Technology Transfer


• USNCCM 2007 Minisymposium– Robust Nonlinear Iterative Methods for Time-Dependent

Unsaturated Flow. Kees, Farthing, et al.– Locally Conservative, Stabilized Finite Element Methods for

Richards’ Equation. Farthing, Kees, et al.– A Computational Tool for Creating Synthetic, Smallscale Infrared

Imagery of Vegetated Soil Surfaces. Peters, Ballard, et al.• Locally Conservative, Stabilized Finite Element Methods for

Richards’ Equation. Kees, Farthing, et al. To be Submitted 10/07 Computational Geosciences

• Local Discontinuous Galerkin Approximations to Richards’ Equation. Li, Farthing, et al. Advances in Water Resources 30, 555-575 (2007).

• Adaptive Local Discontinuous Galerkin Approximations to Richards’ Equation. Li, Farthing, et al. Advances in Water Resources 30, 1883-1901. (2007).

Publications and Related Work


• A numerical model of particle-scale two-phase flow.

• A theory of variably-saturated granular media.

• A numerical model of variably-saturated granular media

• A multi-scale theoretical and computational model of variably-saturated granular media.

Publications


• Porous media experiments– Clint Willson (LSU)– David DiCarlo (UT)– Tissa Illangesekare (CSM)

• Mesh generation– Graham Carey (UT)– Owen Eslinger (ITL)

• Finite Elements– Clint Dawson (UT)– Lea Jenkins and John Chrispell (Clemson)

• Pore-scale and Multi-scale Theory and Computations– Steve Bryant and Masa Prodanovic (UT)– Todd Arbogast (UT)

Collaborations


• Research on physical theory is related to thin film research in industrial mathematics, non-aqueous phase liquid research in environmental engineering, and granular media research in civil engineering.

• Combining fluid mechanics with solid mechanics is an active area in several fields, but no consensus on a standard set of theoretical or computational tools exists.

Assessment of Research Area


Issues• Weak points in the computational infrastructure

– Mesh generation– Visualization– Stability, maturity, availability of HPC

environment– Fast, robust solvers for parallel architectures

• Weak points in the theoretical approach– Non-equilibrium thermodynamics.– Obtaining relevant experimental data and

incorporating into the models.– Accurately modeling the stress jump due to

surface tension and conservation of mechanical energy and mass

one team: relevant... ready... responsive... reliable basic research program particle-scale...

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