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РОССИЙСКАЯ АКАДЕМИЯ НАУК Институт проблем безопасного развития
атомной энергетики
RUSSIAN ACADEMY OF SCIENCES Nuclear Safety Institute (IBRAE)
Modeling unsaturated groundwater flow and
transport in vadose zone using GeRa code
Suskin V.V., Kapyrin I.V., Rastorguev A.V.
5th International Conference HYDRUS Software Applications to
Subsurface Flow and Contaminant Transport Problems
March 30-31 2017
Prague, Czech Republic
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Outline
Plan: 1. A brief description of the GeRa code. 2. Formulation of
four tests and modeling results
presentation along with cross-verification with other codes.
3. Conclusions.
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Aim of the work – unsaturated flow and transport in the vadose
zone models
verification.
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Present-day GeRa capabilities Modeling: • geological, •
groundwater flow, • transport.
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Platform – INMOST (www.inmost.org), Parallelization – MPI,
Unstructured grids – two generators.
http://www.inmost.org/�
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Main modeled processes
1 • Groundwater flow (confined, unconfined, unsaturated);
2 • Advective-diffusive-dispersive transport (homogeneous and
doubleporosity media);
3 • Geochemistry (equilibrium and nonequilibrium, by isotherms
and with the calculation of
reactions);
4 • Radioactive decay chains;
5 • Density-driven flow;
6 • Heat transfer;
7 • Thermal convection with variable viscosity of solutions.
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Performed tests
1. Webb’s capillary barrier problem. 2. Two-dimensional
saturated-unsaturated flow and transport
through heterogeneous vadose zone with radioactive decay. 3.
Experiment on flow and transport of solutes and water in a
drained tray. 4. Two-dimensional unconfined model using pseudo
unsaturated
approach.
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Test 1. Webb’s capillary barrier problem
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Hexahedral grid, 1600 cells. 4 grid domains: • upper and lower
layers are 0.45 m thick, • two medium layers are 0.05 m thick. 3
finite volume schemes: • two-point scheme, • O-scheme, • nonlinear
monotone scheme.
Computational grid
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Test 1. Webb’s capillary barrier problem (results)
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Water saturation
Water head
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Test 1. Webb’s capillary barrier problem (results)
Calculated ratio of the flux through the barrier to groundwater
flow
Reference results
Comparison with FEFLOW: similar results, GeRa demonstrates the
monotonicity while in the solution of FEFLOW
oscillations can be observed.
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Hydrogeological conditions
Water saturation
Test 2. Two-dimensional saturated-unsaturated flow and transport
through heterogeneous vadose zone with
radioactive decay • Heterogeneous media: two rock types. •
Initial conditions: constant pressure head (-4.5 m)
over the domain. • Constant flux on the top (0.01 m/day). •
Constant contaminant concentration in the flux
from the storage pit (C=1000 mg/l).
Transport of contaminant
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VS2DT GeRa
With
out d
ecay
W
ith d
ecay
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Test 2. Two-dimensional saturated-unsaturated flow and transport
through heterogeneous vadose zone with
radioactive decay (results)
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Test 3. Flow and transport of solutes and water in the drained
tray
Experiment*:
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*Thais Paris Anguela. Etude du transfert d'eau et de solutes
dans un sol a nappe supercielle drainee articiellement. Life
Sciences. ENGREF (AgroParisTech), 2004.
In this test two types of grids were used: triangular grid and
hexahedral grid.
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Full saturation region (red), free surface and water heads 20,
30, 40, 50, 60 cm.
Triangular grid
Hexahedral grid
Test 3. Flow and transport of solutes and water in the drained
tray (GW flow results 1)
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Comparison of experimental data with the numerical solution
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Test 3. Flow and transport of solutes and water in the drained
tray (GW flow results 2)
Triangular grid
Hexahedral grid
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KCl concentration in drain:
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first experiment second experiment
Test 3. Flow and transport of solutes and water in the drained
tray (transport results)
Calculated time of the concentration front in both experiments
is the same. Experiment number 1. Simulation using GeRa code
repeats the experimental results and the
simulation results of the experiment by Anguela.
• Experiment number 2. In this experiment, there are differences
in the magnitude of the peak.
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Basic principles of unconfined model using pseudo unsaturated
approach
Basic principles: • Water flow should occur almost
only in the saturated zone (below the water table).
• Minimum knowledge of media parameters needed.
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( )
( )
if ,
if ,
if .
max
minr max
max min
r r
h hh h h h h
hh h
hh
hhφ θ
ϕ
θ ϕ
α ϕ α
=
>
− <
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Test 4. Two-dimensional unconfined groundwater flow
ΔX = 0.1 m, ΔZ = 0.5 m, hleft = 6 m, hright = 3 m. Unconfined
model – MODFLOW, Unconfined model, implemented using pseudo
unsaturated approach – GeRa.
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Test 4. Two-dimensional unconfined groundwater flow
(results)
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Conclusions
As a result it can be said that: Groundwater flow and transport
models in the vadose zone
were verified. The results using GeRa code are close to the
results obtained
using FEFLOW, VS2DT and HYDRUS. Implemented unconfined model
with pseudounsaturated
approach was cross-verified with MODFLOW.
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Thank you for attention!
Modeling unsaturated groundwater flow and transport in vadose
zone using GeRa code OutlinePresent-day GeRa capabilitiesMain
modeled processesPerformed testsTest 1. Webb’s capillary barrier
problemTest 1. Webb’s capillary barrier problem (results)Test 1.
Webb’s capillary barrier problem (results)Test 2. Two-dimensional
saturated-unsaturated flow and transport through heterogeneous
vadose zone with radioactive decayTest 2. Two-dimensional
saturated-unsaturated flow and transport through heterogeneous
vadose zone with radioactive decay (results)Test 3. Flow and
transport of solutes and water in the drained trayTest 3. Flow and
transport of solutes and water in the drained tray (GW flow results
1)Test 3. Flow and transport of solutes and water in the drained
tray (GW flow results 2)Test 3. Flow and transport of solutes and
water in the drained tray (transport results)Basic principles of
unconfined model using pseudo unsaturated approachTest 4.
Two-dimensional unconfined groundwater flowTest 4. Two-dimensional
unconfined groundwater flow (results)ConclusionsThank you for
attention!
