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Volker Clausnitzer

Introduction to FEFLOW

DHI Groundwater Modelling Centre

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FEFLOW More than GroundwaterFEFLOW handles groundwater flow and related processes in one software environment, one user interface, and one simulation model:

Variably saturated flow Contaminant transport Heat transport Density-affected flow Chemical reactions And more ...

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FEFLOW More than GroundwaterPrimary development goal: FEFLOW is intented to be

Easy to use and intuitive to quickly master everyday groundwater projects,

but at the same time

Powerful and comprehensive to model complex subsurface processes.

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Complex Processes - Geometry Finite-element discretization Triangular or quad elements (2D) Prisms or cuboids (3D) 3D or 2D horizontal/vertical/axisymmetric projection 1D and 2D for fracture/pipe/borehole flow

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Complex Processes - PhysicsGroundwater and vadose-zone flow

Saturated flow (Darcy law) Unconfined conditions (different approaches) Unsaturated / variably saturated flow (Richards equation) Fracture flow Density- and viscosity-dependent flow

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Complex Processes - PhysicsTransport

Heat transport (advection-conduction equation) Solute transport (advection-diffusion equation) Combined solute/heat transport Sorption, Decay Multispecies simulation Kinetic reaction systems

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Ease of use

User interface for preprocessing, simulation, and postprocessing GIS/CAD/ASCII file interfaces for import and export 2D/3D map support Advanced computational methods

Powerful mesh generators Automatic time-stepping scheme Algebraic multigrid solver Parallelization

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Visualization

2D top / cross-section views 3D views

2D / 3D map support 3D clipping and carving Live, interactive visualization

during simulation run

Hardware acceleration via OpenGL

3D stereoscopic display/projector support currently in betatesting

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FEFLOW Viewer Free (no license required) Works with existing FEFLOW models Visualization and analysis Export of figures and animations Model and results files Use by modeler

No license necessary for postprocessing

Share your model with colleagues even if licenses are limited

Usage by consulting clients No need to purchase an additional license

Deliver viewable model files to customers

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Extensibility Open programming interface

Documented API interface User can develop plug-ins for

oAdditional functionalityoWorkflow automation

Application Examples Groundwater / surface water coupling Integration of technical installations in geothermal modeling Import of model properties Export of model results

Development Services Plug-in development as a consulting service

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Fields of Application Regional groundwater management

Mine water management

Construction and tunneling

Groundwater surface water interaction

Agriculture (irrigation, drainage, salinization, nutrient management)

Remediation / natural attenuation

Capture-zone delineation

Saltwater intrusion

Geothermal energy

Industrial porous materials

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FEFLOW Community

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FEFLOW Community

www.feflow.info/forum

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User Support We help by

Giving advice on FEFLOW modeling

Analyzing possible model improvements

Explaining theoretical background and functionality

In addition, we offer Training courses Solutions Software customization Consulting in modeling

projects Model review

FEFLOW ServicesTeam

Support Training Plug-in Solutions

Dipl.-Ing. Alexander Renz

Dipl.-Ing. Julia Mayer

Dipl.-Ing.Bastian Rau

Dipl.-Ing. Peter Schtzl

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Why FEFLOW? Highly scalable software package

Different feature levels available Optimal cost efficiency for every application Upgrades possible at any time

One software for current and future projects No need for additional software and training Saves time and money

Commercial software DHI guarantees consistent services Close contact to support staff Software performance benchmarked and documented Quality assurance Ongoing development

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Application Examples

1. Optimization of landscape water regime

2. Construction of an underground liquefied natural-gas storage system

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Agricultural Development PlanningGlietzener Polder, Germany

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ObjectivesConcept for landscape water regime that accommodates agricultural, environmental, and general landscape water balance goals:

Improvement of agricultural conditionsSustainment of low-water discharge, securing of minimum discharge in low-water periodsImprovement of groundwater and surface water qualityFlood protectionImprovement of the ecological role of water bodies

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Potential for conflict

AgricultureEnvironment

Landscape waterbalance

Conflicting Objectives

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Approach

1. Calculation of groundwater and surface water levels applying a coupled GW-SW model for different system states

2. Calculation of depth to groundwater using the groundwater levels and a DEM

3. Intersection of depth to groundwater with defined target levels, definition of areas of conflict

4. Simulation of scenarios lowering the potential for conflict, using the target levels as goal for future planning

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FEFLOW

Coupled Model FEFLOW-MIKE11

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Target Compliance, Initial State (March)

too drytoo wetacceptable

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Planned Measures Modification of target water levels for pumping stations Adaptation of structures, change of storage levels Installation of weirs and low weirs (ground sills) Desludging of ditches Closure of Altreetz pumping station

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Mrz (Plan - Ist)[m]

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Entschlammungs-strecken

Predicted Change in Water Level

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SW-Gebiet Paulshof I

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Area Controlled by Pumping Station Paulshof I

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Cavern Construction for LNG Storage

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Ice RingIce Ring

InsulationInsulation

Stainless Stainless SteelSteel

CavernCavernLNG

-162 C

Principle

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Simulation Objectives

Represent the dewatering process over a 4-year construction period with a complex construction schedule

Inflow/drainage for all parts of the underground structure Impact on groundwater level in the surrounding area Seawater intrusion potential

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Density-dependent variably saturated flow

Advective-dispersive transport of dissolved constituents

Physical Processes

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Model Domain

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Model Domain

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Superelement mesh

253 polygons

463 lines

Spatial Discretization

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Finite-element mesh

956,125 elements

498,914 nodes

Spatial Discretization

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Finite-element mesh Cavern structures

Spatial Discretization

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Finite-element mesh Cavern structures

Spatial Discretization

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Saturated conductivity

Porosity

Granitic Gneiss 10-910-8 m/s 1%

Mica Schist 10-7 m/s 1%

Altered zone 12 x 10-6 m/s 5%

Insulation 10-11 m/s 1%

Material Properties

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Kr = Seff

Seff = (1 + ||-n)-m

= 2

= 0.1 m-1 n = 1.964 m = 0.509

Effective saturation vs. Pressure head

Relative conductivity vs. Effective saturation

Material Properties

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Groundwater recharge

Boundary Conditions

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Flow (Hydraulic head)

Dirichlet condition along coastline

No-flow (zero-value Neumann) condition elsewhere

Transport (Solute concentration)

Dirichlet (fixed-concentration) condition for infiltrating seawater along coastline

Zero-value Neumann condition for fluid leaving domain along coastline

Impermeability condition elsewhere

Boundary Conditions

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Internal surfaces of the structure are treated asSeepage face

Dirichlet condition of fixed atmospheric pressurefor outwarding-pointing head gradient

No-flow (zero-value Neumann) condition otherwise

Boundary Condtions

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Simulation requires successive activation of seepage-face B.C.s as construction progresses.

New B.C.s must continuously be introduced during the simulation.

Solution:

Seepage-face activation via a separate module using the FEFLOW Open Programming Interface:

arbitrary node groups and activation intervals

arbitrary pressure

import capability from ASCII files

saves all information with the problem file

Transient Boundary Conditions

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Steady-state head and solute-concentration distributions obtained for undisturbed conditions

Initial Condition

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0 d0 d 360 d360 d

720 d720 d 1080 d1080 d

Pressure

Simulation Results

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Pressure

0 d

360 d

720 d

1080 d

Simulation Results

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Solute concentration

Simulation Results

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Groundwater table

Simulation Results