2-D Numerical Simulation For Fate of Oil Spills

 

Two-dimensional numerical simulation for transport and fate of oil spills in seas

Project submitted by:Prakash Prasad(BE/1398/2011) Satyam Jha(BE/1408/2011) Amrit Ranjan(BE/1443/2011)

 

OUTLINE 

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Overview of Oil spill Causes Impact Predicting challenges Oil Spill Response Techniques Mathematical Modeling Bohai Sea Oil Spill Response Options Calculator (ROC)

 

Oil Spill: Overvie Over view w  An “Oil Spill” Spill” usually refers to an event that that led to a

r el elea eass e of lili qui quid d pet petr ole oleum um hydroc hydr oca ar bon into i nto the envirr onme envi onment nt due due to to human human ac ac ti vi vity ty and and is i s a for form m of  pollution  pollutio n

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Oil spills are inher inherently ently multi-component/phase (oil/gas/wa (oil/gas/water), ter), unsteady, locally-turbulent, with buoyancy, phase change, chemistry and other complex physics. It is important to understand the fate, transport and physical distribution of the oil/gas discharge under realistic sea and atmospheric-wind conditions. Knowledge Knowledge of this distribution distr ibution impacts marine life, pollution, and healthy and safety.

 

Causes 

Release of crude cr ude oil - Tankers, offshore offshore platforms, drilling rigs and wells wells

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Releasee of refined petro Releas petroleum leum product productss - Large ships such such as

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 bunker fuel and storage tanks Sinking or leakage of Oil carrying carr ying vessels or Oil pipelines Illegal dumping by industries

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Countries at war Terrorist activities Natural disasters

 

Impact of Oil Spill Event and Mitigation 

Effects entire marine life

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Blocks entrance of oxygen in water

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Fishes hatch with twisted spines and deformed hearts

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Effects the food web when oil reaches sea bed be d Natural recov recovery ery process may may require upto upto 10 years

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Cost of clean-up is huge

 

Predicting Challenges Ocean Hydrodynamics

Complex Physics

 Advection

 Evaporation

 Turbulent  Surface

Diffusion

Spreading

 Dissolution  Emulsification

 Hydrolysis  Photo-Oxidation  Bio

Degradation  Particulation

 

Transport and Fate of Oil Slick in Seas

 

Oil Spill Response Techniques 1.

Mechanical containment or recovery recovery: It is the primary line of defence against oil spills. Containment and recovery equipment includes a variety of booms, barriers, and skimmers, as well as natural and synthetic sorbent materials.

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booms are floating barriers to oil

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Skimmers are boats that skim (scoop) spilled oil from the water surface

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Sorbents are big sponges used to absorb oil

2. In Situ Burning: It is a method of burning freshly spilled oil, usually while it's floating on the water.

 

3. Chemical and biological methods: It can be used in conjunction with mechanical mechani cal means for containing and cleaning up oil spills. Dispersing agents and gelling agents are most useful in helping to keep oil from reaching shorelines. sh orelines. Biological agents have the potential to assist recovery recovery in sensitive areas such as shorelines, marshes, and wetlands. 4. Physical methods: Used to clean up shorelines. Natural processes such as evaporation, oxidation, and biodegradation can start the cleanup process, but are generally too slow to provide adequate environmental recovery. Physical methods, such as wiping with sorbent materials, mater ials, pressure washing, and raking and bulldozing can be used to assist these natural processes.

 

Mathematical Modeling Computational Fluid Dynamics

Navier Stokes Equation

• Computational fluid dynamics (CFD) is the use of applied mathematics, physics physics and computati comp utational onal ssoftwar oftwaree to vvisua isualize lize hhow ow a gas or liquid flo flows ws -- as w well ell as how how the ggas as or liquid affects objects as it flows past. Computa Computational tional fluid dynamics is based on the NavierStokes equations. These equations describe how the velocity, pressure, temperature, and density of a moving fluid are related.

• The Navier-Stokes equations are the fundamental partial differentials equations that describe the flow of incompressible fluids. f luids. viscosity scosity and ggravity ravity respectively • Fp + Fv + Fg = 0 where p, v & g stands for pressure, vi

• The Navier Stokes equation was applied to the model using ROC(open Source) • The Response Options Calculator can be used to t o assess system performance involving mechanical recovery, dispersant application, and the burning of oil. ROC predicts how the Response Option spilled oil will weather over time and the volume of oil that can be recovered, burned, or treated for the response systems selected. Calculator

 

 An example of CFD Modeling for for Deep Sea Oil spills

 

Bohai Sea Oil Spill 

Bohai Sea Bohai Sea is the inne innermost rmost gulf gulf of theY theYello ellow w Sea Sea on the the coast coast of North North-e -eas aste tern rn and and North North Chin Chinaa

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Bohai Sea is a half closed sea with comparatively low low self

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clean ability due to limited water exchange with outside The Bohai Oil spill spill took place place in the Penglai Penglai 19-3 oil field field on  June 4, 2011 and follow followed by other other two two spills on 17th  June and 12th July Oil Spill occurred at 38o N, 120o E

 

Bohai Sea and location of Oil Spill 

 

Response Options Calculator ROC) The Response Options Calculator (ROC) (ROC) indicates general performance for oil spill response systems. It cannot be used to determine exact values due to highly variable variable input parameters, process complexity, and inter-dependencies. ROC is basically used for: 

Predict spreading and weathering weathering of oil spilled spil led on the water surface

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Estimate the volumes of oil that could be affected by skimmers, dispersant applications, and in-situ burning.

 

Assumptions and Limitations of ROC 

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ROC is not a trajectory model. It is not geo-specific. It is intended for modelling spills in open water outside of the influence of tides, land, ice, or debris. ROC assumes “best industry practices”, i.e., that response occurs in the thickest oil. To simplify computations, ROC holds some factors constant that in reality could change

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ROC can’t model to very thin oil slicks or “sheens” (~ 1 micron, or ~response 10-4 inch). ROC simulations may not have a duration greater than 5 days.

 

Input parameters for simulation Parameter

Case

Date

4th June of 2011

Latitude

38o N

Longitude

120o E

Oil Type

Fuel No.2(High aromatic content heating oil)

Release type

Instantaneous

Simulation time

4 days (96 Hours)

Ices cover condition

None

Spill Volume

240 m3 or 1500 bbl

Wind Velocity

4-6 Km/hr  

Water Temperature

22oC  –  28oC

Water Viscosity

1.15 cSt(centistokes)

Oil Viscosity

2 cSt(centistokes)

 

Results Obtained from ROC

Area covered(Km2) vs time(h time(hours ours))

 

Evaporation(m 3) vs tim time(h e(hours ours))

 

Oil aff affecte ected(%) d(%) vs time( time(hours) hours)

 

Oil thickness (cm) vs time(h time(hours) ours) thickness(cm)

 

Pie chart of oil affected by various parameters(m3)

 

Oil viscosity(cTs) vsTime(hours)

 

Oil volume(m3) vs Time(hours) Time(hours)

 

Conclusion Prevention is a key component to fight Prevention figh t accidental pollution and that includes: 

Designing facilities that are increasingly reliable, safe and

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efficient. Conducting maintenance and inspection campaigns on a very regular basis.

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Using leak detection devices.

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Scheduling regular audits.

Selecting means of transportation and routes that limit the risk of accidents.