University of Vienna
Transcript of University of Vienna
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Numerical study of acoustic wavesaround and inside an underground cavity
CTBTO Young Scientist Research Award 2014
WWTF project 2015
Sofi Esterhazy, Ilaria Perugia, Joachim Schoberl, Gotz Bokelmann
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Wave animation
Scattered wave field Zoom
Sofi Esterhazy University of Vienna 2 / 13
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Objectives
Contribution to the scientific groundwork for OSI
Numerical investigation
Development of new method for elastic-acoustic problemsImprovement of computational algorithms
Applied investigation
Define characteristics of wave field interactionsImprove and design methods and experiments
Sofi Esterhazy University of Vienna 3 / 13
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On-Site Inspection
Launch Pre-Inspection Inspection Post-InspectionRequest of OSI
Equipment - Training/Field tests - OSI Action Plan
Techniques IFE08 IFE14 Techniques IFE08 IFE14
Visual Observations Environmental measurements
Seismological aftershock monitoring Electrical conductivity measurements
Gamma radiation monitoring Air-borne gamma spectroscopy
Magnetic field mapping Active seismic survey
Gravitational field mapping Resonance seismometry
Multi-spectral imaging Drilling
Argon-37 and radioxenonmeasurement
Key: Tested, Partly tested, Not tested
Sofi Esterhazy University of Vienna 4 / 13
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Seismic Methods
Subsurface structure after an UNE
(Adushkin
&Spivak,2004)
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Simplified model
2
1
?
Sources:
Passive seismic sources: Body waves, Surface waves, Noise
Active seismic sources: Vibroseis, Explosions
Sofi Esterhazy University of Vienna 5 / 13
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Underling physics
Acoustic wave equation in medium 1 2
1
?
Elastic wave equation in medium 2
Focus on compressional waves
Time harmonic cases:
Spherical point source?
Plane wave sources
Sofi Esterhazy University of Vienna 6 / 13
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Underling physics
Acoustic wave equation in medium 1 2
1
?
Elastic wave equation in medium 2 Focus on compressional waves
Time harmonic cases:
Spherical point source?
Plane wave sources
Sofi Esterhazy University of Vienna 6 / 13
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In/Out Scattering
Separation into the incident and scattered wave field:
p = pinc + pscat
pinc
pscat
Better inside to the wave field interaction
Sofi Esterhazy University of Vienna 7 / 13
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Numerical results (1)
Scattered wave field from a plane wavefrom the bottom left with f = 16Hz
Cavity at depth D = 600m and diameter d = 60m
Material parameters:v1 = 300m/s, 1 = 1kg/m
3
v2 = 3000m/s, 2 = 1000kg/m3 Incident wave field
Without Cavity With cavity
Sofi Esterhazy University of Vienna 8 / 13
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Numerical results (1)
Scattered wave field from a plane wavefrom the bottom left with f = 16Hz
Cavity at depth D = 600m and diameter d = 60m
Material parameters:v1 = 300m/s, 1 = 1kg/m
3
v2 = 3000m/s, 2 = 1000kg/m3
Netgen/Ngsolve
Automatic 2D/3D adap-tive mesh generator
High-order Finite Element Method Applicable for Heat-flow, Acous-
tics, Elasticity, Navier-Stokes,Maxwell, etc.
Open-source, C++, MPI parallel,Python Plugin
Without Cavity With cavity
Sofi Esterhazy University of Vienna 8 / 13
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Numerical Results (2)
Scattering profile
No surface
Total field Scattered field
Geometrywith PML
Plane wave from the bottom with f = 16Hz
Cavity at depth D = 600m and diameter d = 60m
Material parameters:v1 = 3000m/s, 1 = 1000kg/m
3, v2 = 300m/s, 2 = 1kg/m3
kR = 1
Sofi Esterhazy University of Vienna 9 / 13
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Numerical Results (2)
Scattering profile
No surface
Total field Scattered field
Zoom
Plane wave from the bottom with f = 16Hz
Cavity at depth D = 600m and diameter d = 60m
Material parameters:v1 = 3000m/s, 1 = 1000kg/m
3, v2 = 300m/s, 2 = 1kg/m3
kR = 1
Sofi Esterhazy University of Vienna 9 / 13
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Analytic Approach (Felix M. Schneider)
Express the incident and the scattered wave field by linearcombinations of spherical vectors and solve a system of linearequations
For each index l find the coefficients to match at the boundary r = R
Sofi Esterhazy University of Vienna 10 / 13
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Scattering cross sections(Valeri Korneev, Geophys. J. Int. (1993))
S = Ein/Escat . . . Ratio between scattered and incoming energy flow
kR = U/ . . . Ratio between cavity circumference and incident wavelength
Vacuum inclusion Acoustic inclusion
Modeling the cavity as an acoustic inclusion is crucial to resonanceseismometry
Sofi Esterhazy University of Vienna 11 / 13
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Summary & Outlook
Project distinguished by the Young Scientists Research Award
Wave propagation with focus on acoustic case
Identification of underlying physics
Investigation of characteristics (analytically and numerically)
Set up of an efficient numerical code
Extension to full elastic wave field
Extension to 3D
Numerical improvement and Post-processing
Incorporation of our findings into the practices of an OSI
Thank you!
Sofi Esterhazy University of Vienna 12 / 13
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Summary & Outlook
Project distinguished by the Young Scientists Research Award
Wave propagation with focus on acoustic case
Identification of underlying physics
Investigation of characteristics (analytically and numerically)
Set up of an efficient numerical code
Extension to full elastic wave field
Extension to 3D
Numerical improvement and Post-processing
Incorporation of our findings into the practices of an OSI
Thank you!
Sofi Esterhazy University of Vienna 12 / 13
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In/Out Separation
Ansatz p = pinc + pscat
pinc solves
2pinc + k1pinc = (x x0) + rad. cond. for x x0
The remaining unknown pscat is then the solution of
(
1
1pscat
)+
k11
pscat = 0 in 2
(
1
2pscat
)+
k22
pscat =1
2(k1 k2)pinc in 1
pscat = pinc on
+ radiation condition for r
Sofi Esterhazy University of Vienna 12 / 13
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Numerical method
High-Order Finite Element Method
Can handle highly complex, irregularly shaped geometriesTends to exponentially increase the accuracy of the computations
Software
Netgen: Automatic 2D/3D tetrahedral adaptive mesh generatorNgsolve: Applicable for Heat-flow, Acoustics, Elasticity,Navier-Stokes, Maxwell, etc.Open-source, C++, MPI parallel, Python Plugin
Hardware
Internal server with 48 coresVienna Scientific Cluster 3 - 140/2020 dual nodes a 8 cores
Sofi Esterhazy University of Vienna 13 / 13
ObjectivesApproachResults