modelling magma intrusion into an underground opening presentation to volcanic eruption mechanism...
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Modelling Magma Intrusion into an Underground Opening
Presentation to
VOLCANIC ERUPTION MECHANISM MODELING WORKSHOP
November 14-16, 2002
University of Hew Hampshire
Durham, NH 03824, USA
Ed Gaffney and Rick RauenzahnLos Alamos National Laboratory, Los Alamos, NM 87545, USA
Modelling Magma Intrusion into an Underground Opening
Context of Yucca Mountain (Ed)–Geologic Setting–Repository Requirements–Potential Igneous Events–Goals of Modelling
CFDLIB (Rick)–Background and Basics–Version 02.1
•Volatile exsolution•Variable viscosity
Early results (Ed)–Initial Interactions–Effusive Flow
Context of Yucca Mountain
Geologic Setting– Fault block in rhyolitic tuff sequence
• Tertiary• Water table ~600 m,repository ~300 m
– Pliocene to Pleistocene basaltic eruptions• Closest (Lathrop Wells Cone) is 75 ka• ~0.15 km3
• Alkali basalt, 2-4 wt/o water
Context of Yucca Mountain
Repository Requirements– Exposure of target population
• Over 10,000 year span
– Potential hazards • Ground water seepage• Damage to waste packages from seismic activity• Volcanic intrusion
Context of Yucca Mountain
Potential Igneous Events– Unlikely (10-8 per year)– Intrusive/extrusive event similar to Lathrop wells
• alkali basalt• 1-4% (wt) H2O• ~0.1 km3
– Dike intersects drifts, damages waste packages• gas corrosion• heat effects on integrity• Impact, drag
– May erupt to surface• fissure, conduit, or dogleg
Context of Yucca Mountain
Goals of Modelling– Determine environment seen by waste packages
• Is there a shock from first eruption into drift?• Will magma fill drift?• Size and velocity of projectiles?• Peak environments (P, T, u, dynamic pressure) along drift• “Final” environments
– Evaluate mechanisms for release• Impacts of bombs, other fragments• Heating internal gas P rises rupture• Drag effects (carried to surface, torn by diff. drag forces, ...)
CFDLIB Background
• Multiphase compressible and incompressible flows– 10 years in development– Test bed for models– Applications in industry, defense
• Collocated (cell-centered) variables– Fluxing velocities are time-space advanced with pressure
correction
• ICE/MAC– Pressure waves treated implicitly (relax SS Courant
condition)– Advection/viscosity explicit– General EOS, multiphase exchange laws (user)
CFDLIB Background (cont’d)
• Particle-in-cell method– Allows mixed Lagrangian/Eulerian treatment– State variables (m, U, x, , …) kept on particles
that move with interpolated velocity– Fluid/structure interaction (history-dependent
stress laws)
• Example with rod penetrator
CFDLIB Background Elastic Rod Penetrator
CFDLIB Background Brittle Rod Penetrator
CFDLIB Background YMP special needs
• Vapor/magma equilibrium– Papale (1997, 1999)– Include air (extend K/J EOS by assuming ideal air)
• Variable (high) viscosity– Implicit treatment– Model of Shaw (1972)
• Generalized effective drag/heat transfer– Particle size/coefficients as f(k,Tk,...)
• Equations of state for gas (BKW) and liquid(Us-Up)
Early ResultsMagma /Tunnel Interaction
Early ResultsMagma /Tunnel Interaction
X
Y
0 200 400 6000
250
500
P130.0
60.328.013.0
6.02.81.3
N = 1296
Frame 001 10 Sep 2002 FLIPICE: Blast wave from steam-filled maFrame 001 10 Sep 2002 FLIPICE: Blast wave from steam-filled ma
Early ResultsGas Jet
A 20 bar gas jet expands into an atmosphere
X
Y
0 500 10000
100
200
300
400
500
600
700
800
900
1000
1100
1200
V87.6081.2974.9768.6662.3456.0349.7143.4037.0830.7724.4518.1411.83
5.51-0.80
CFDLIB 99.2
T = 1.000E+03N = 27061
Frame 001 17 Oct 2002 FLIPICE: Blast wave from steam-filled maFrame 001 17 Oct 2002 FLIPICE: Blast wave from steam-filled ma
Conclusions
• Goal: model magma drift interaction
• CFDLIB is multifluid, multiphase code• Mixed Lagrangian/Eulerian facilitates fluid-structure interaction• Implicit treatment of pressure waves• User supplied equation of state and exchange laws• Volatile equilibrium with silicate liquid like Papale but with different equation of state• Variable (high) viscosity
• Work has just begun and team is small• magma expansion into drift• effusive flow in drift (~ lava tube)• gas jet from a circular vent