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Modelling Magma Intrusion into an Underground Opening: 

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 Rauenzahn Los Alamos National Laboratory, Los Alamos, NM 87545, USA

Modelling Magma Intrusion into an Underground Opening: 

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: 

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: 

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: 

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: 

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: 

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): 

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 Elastic Rod Penetrator

CFDLIB Background Brittle Rod Penetrator: 

CFDLIB Background Brittle Rod Penetrator

CFDLIB Background YMP special needs: 

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 Results Magma /Tunnel Interaction: 

Early Results Magma /Tunnel Interaction

Slide14: 

Early Results Magma /Tunnel Interaction

Slide15: 

Early Results Gas Jet A 20 bar gas jet expands into an atmosphere

Slide16: 

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

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