Modeling the Spreading of Large LNG Spills on Water
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environmental • failure analysis & prevention • health • technology development A leading engineering & scientific consulting firm dedicated to helping our clients solve their technical problems. Modeling the Spreading of Large LNG Spills on Water Harri K. Kytömaa, Ph.D., P.E. Nicolas F. Ponchaut, Ph.D. October 27-28, 2009
Modeling the Spreading of Large LNG Spills on Water
PowerPoint PresentationA leading engineering & scientific
consulting firm dedicated to helping our clients solve their
technical problems.
Modeling the Spreading of Large LNG Spills on Water
Nicolas F. Ponchaut, Ph.D.
Solutions to governing equations (Exponent Spill Model, ESM)
Instantaneous release of finite spill
Instantaneously started constant spill rate
Test cases: typical Coast Guard IRA spill
Conclusions
Effect of friction on the pool
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Assumptions
ABS/FERC friction: smooth, 0.063 mm vapor layer
F LE CI
Neutrally buoyant equilibrium at each location
Uniform evaporation rate
K = 1.4: Suchon, 1970 (oil spills)
K = 1.34: Raj and Kalelkar, 1974
K = 2.0: Briscoe and Show, 1980
K = 1.64: Chang and Reid, 1982 (liquid n-pentane)
K = 1.16: Effective value used by GASP, 1990
K > 4: PHAST
LELE hgKU *
Reality: constant height and stagnant initial condition
Similarity distribution: thickness and radial speed
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250 m pool at steady state
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Sudden flow rate increase
24,890 kg/s for t < 400 s (250 m pool radius at
equilibrium)
35,840 kg/s for t > 400 s (300 m pool radius at
equilibrium)
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Sudden flow rate decrease
24,890 kg/s for t < 400 s (250 m pool radius at
equilibrium)
15,930 kg/s for t > 400 s (200 m pool radius at
equilibrium)
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GASPExponent Spill Model
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Upstream of the headwave (closer to the spill location):
Downstream of the headwave (closer to the pool edge): Flow is
subcritical: U2 < g* h The flow goes slower than the wave
propagation speed
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Conclusions 1 MODELS
Upstream of the headwave, the pool thickness profile is largely
independent of downstream conditions
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The interface can be rough, and exhibit significant
turbulence
For spills of large surface area, friction will impact the
character of the pool
Using the “vapor layer” friction model results in a headwave that
separates from the pool
With a turbulent friction model, the headwave decays and remains
attached to the pool
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Conclusions 3 POOL SIZE
If the friction is assumed to be low, the headwave propagates and
separates as a ring that evaporates away
With more realistic turbulent friction, the headwave does not
separate
Turbulent friction results in slower pool growth and smaller
maximum pool size
Slide Number 1
GASP (Gas Accumulation over Spreading Pools, Webber 1990)
Exponent Spill Model: ESM
Instantaneous release
Instantaneous release
Instantaneous release
Steady spill rate
Steady spill rate
Steady spill rate
Steady spill rate
Steady spill rate