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Numerical Modeling of Explosively Loaded
Concrete Structures Using a Coupled CFD-
CSD Methodology
Michael E. Giltrud, Joseph D. Baum, Orlando A. Soto
Fumiya Togashi; Applied Simulations Inc.
Rainald Löhner; George Mason University
International Explosive Safety Symposium, 9 August 2018
2
Outline
• Methodology
• Background
• Kasun Finite Element Model
• Kasun Finite Element Analysis• 1 - 6.9kg Bare Charge
• 16 - 6.9kg Bare Charges
• 1 - 155mm Cased Charge
• 16 - 155mm Cased Charges
• Summary and Conclusions
3
Flow Solver: FEFLO
Adaptive, unstructured grids (triangles/tetrahedra)
Compressible & incompressible flows
Inviscid, laminar & turbulent flow
Several turbulence models (MILES, Smagorisnky, Baldwin-Lomax, Spalart-Allmaras, K-Epsilon)
Explicit and implicit time stepping
EOS: Real air, water (Tate), SESAME, polynomials, tables
State-of-the-art shock capturing numerical schemes (Roe, FCT, HLLC, ENO, WENO, DG…..)
Body-fitted ALE or embedded for moving bodies/change of topology
Edge-based FE data structure
Kinetic combustion modeling
JWL (HE, non-ideal HE), Miller after-burn models, Cheetah
Particles as a dilute phase
Exchange of mass/momentum/energy with flow
Extensive benchmarking and validation
International group of users (in many disciplines)
4
Structural Dynamics Solver: ASICSD
ASICSD:
CSD solver: specifically for large, plastic deformations
Beams, shells & solid elements
Elastic, plastic, viscoelastic materials
Various concrete models
Rivets, bolts etc.
Erosion model, but
Cracking, rather than erosion for structural break-up
Mott’s model for weapon case break
Johnson and Cook model for thermal softening
Non-reflecting BC
5
MASTER: FEMAP
Find Interpolating Parameters
Between CFD & CSD Meshes
Faces and Nodes
Use Octree for fast Search
Impose stress Loads
(p, v), heat flux
CFD -> CSD
Impose Boundary
Displacement,
Velocities
CSD -> CFD
CFD/CSD Loose Coupling Approach
CFD - FEFLO
CSD: ASICSD
Transfer Interface Mesh
Transfer Interface Mesh
6
Background
• Background:• In 2008, a joint Norwegian and Swedish
experimental program was conducted to examined the detonation of explosives within concrete ammunition storage structures
• The program focused on pressure occurring from detonation and the debris thrown caused by the detonation
• The concrete structure known as Kasun III was 2m x 2m x 2m having nominal wall thickness of 150mm
7
Kasun Finite Element Mesh
8
Kasun III Configuration and Charge
1 – 6.9kg Bare Charge
9
Pressure Comparisons
1 – 6.9kg Bare Charge
Pressure gauges located
on internal wall
P1-Pressure on Lower Left
P4-Pressure on Upper Left
Experimental Pressure
Experimental Impulse
Calculated Pressure
Calculated Impulse
10
Peak Pressure Versus Range
1 – 6.9kg Bare Charge
Range (cm)
Pea
k P
ress
ure
(psi
)
Pressure Off The Side
200 300 400 500 600 700 800 1000 2000 3000 4000 50000.20.2
0.3
0.5
0.7
1
2
3
5
7
10
FEFLO Pmax (psi)Exp Pmax (psi)
Range (cm)
Pea
k P
ress
ure
(psi
)Pressure Off The Back
200 300 400 500 600 700 800 1000 2000 3000 4000 50000.2
0.3
0.5
0.7
1
2
3
5
7
10
FEFLO Pmax (psi)Exp Pmax (psi)
11
Kasun III Configuration and Charge
16 – 6.9kg Bare Charges
12
Pressure Comparisons
16 – 6.9kg Bare Charges
Pressure gauges located
on internal wall
P3-Pressure on Lower Right
P6-Pressure on Upper Right
Experimental Pressure
Experimental Impulse
Calculated Pressure
Calculated Impulse
13
Pressure/Impulse Versus Range
16 – 6.9kg Bare Charges
Range (cm)
Pea
k P
ress
ure
(psi
)
KASUN 110kg Bare ChargeBack Radial
200 300 400 500 700 1000 2000 3000 4000 5000 7000 100000.50.7
1
2
3
57
10
20
30
5070
100
200
300
500
Pmax (psi) FEFLO CalculationPmax (psi) Experiment
Peak Pressure vs Range Peak Impulse vs Range
14
Kasun III Configuration and Charge
1 – 155mm Cased Charge
15
Kasun Structural Response1 – 155mm Cased Charge: 14 ms
Model reproduces:
• Bulging in middle bottom of wall
• Separation of walls from floor
• Crack in corner to roof
• Initial separation of roof from walls
16
Pressure Comparisons
1 – 155mm Cased Charge
Time (ms)
Pre
ssur
e (k
Pa)
x 1
000
Impu
lse
(kP
a-se
c)
Station 1 - Lower Right
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-2 -3
-1 -1.5
0 0
1 1.5
2 3
3 4.5
4 6
5 7.5
6 9
7 10.5
8 12
9 13.5
10 15
11 16.5
12 18Comparison P1
ExprimentCalculationImpulse ExprimentImpulse Calculation
Pressure gauges
located on internal
wall
Upper Left
Lower Left
17
Peak Pressure Versus Range
1 – 155mm Cased Charge
Peak Pressure vs Range
Range (m)
Pea
k P
essu
re (
psi)
Kasun 1 - 155mm Charge
2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 1000.02
0.03
0.05
0.07
0.1
0.2
0.3
0.5
0.7
1
2
3
5
7
10
2020CalculationExperiment
Big Percentage though
only 1 psi
18
Kasun III Configuration and Charge
16-155mm Cased Charges
19
Kasun Structural Response16 – 155mm Cased Charges: 2.8 ms
Model reproduces:
• Bulging in middle bottom of wall
• Separation of walls from floor
• Crack in corner to mid height
• Initial separation of roof from walls
20
Pressure Comparisons
16 – 155mm Cased Charges
Time (msec)
Pre
ssu
re (
kP
a x
1000)
P5 - Upper Middle
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-5
-2.5
0
2.5
5
7.5
10
12.5
15
17.5
20
22.5
25
27.5
30Comparison P5
ExperimentCalculation
Pressure gauges
located on internal
wall
Upper Right
21
Peak Pressure Versus Range
16 – 155mm Cased Charges
Peak Pressure vs Range
Range (m)
Pea
k P
ress
ure
(psi
)Kasun 8 - 155mm Cased Carges
2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 1000.5
0.7
1
2
3
5
7
10
20
30
50
70
100
200
300
500CalculationExperiment
22
Summary of Kasun Analyses
• Bare Charge Analyses– Calculated internal pressure data represent the TNO experimental data
reasonably well though there are differences
– Computed pressure vs range attenuation is nearly identical to the
experimental though the magnitude is slightly greater
• Cased charge analyses– Calculated internal pressure data represent the TNO experimental data
reasonably well though there are differences
– Computed pressure vs range attenuation has the correct trend
compared to the experimental though the magnitude is greater
– Fragments do considerably more damage to the lower structure than the
bare charge
23
Conclusions/Recommendation for
Kasun Analyses
Conclusions
– Bare Charge Analyses
• The results of the calculation generally reproduce the experimental results
following trends and amplitudes within about 20% or a few psi at far field.
– Cased charge analyses
• The results of the calculation generally reproduce the experimental results
following trends and amplitudes within about 30% or a few psi at far field.
Recommendation
– Though pressures and debris launch velocity are useful, the
primary metric for these test is the observed debris field.
• The ability to automatically load the coupled-code fragment data into an
accepted trajectory code would be helpful.
24
Questions?