Numerical Simulation of Oil Spill in Nanri Island Channel Based on

the MIKE Spill Analysis Model

Cui Wang, Shang Jiang, Zhouhua Guo and Qingsheng Li

Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China.

Email: liqingsheng@tio.org.cn.

Keywords: Mike spill analysis model, numerical simulation, oil spill, Nanri Island Channel, marine environment

Abstract:

Based on the MIKE spill analysis model, the oil spill model was built in the sea area around Nanri Island,

and then the drift path and the influence of oil film were simulated under the dominant wind conditions (the

northeast wind). Ten tons of fuel oil was set as the initial spill to model the oil-spill diffusion process over

48 hours. The results showed that the oil spill drift in the sea was mainly influenced by tide and wind, while

the tide played a dominant role. The migration trend of the oil film was different under different wind

conditions. The total area after oil spill was 190.81km

, 142.95km

and 11.71km

under the dominant wind

conditions with oil concentration exceeded 0.05mg/L, 0.3mg/L and 0.5mg/L, respectively. In general, the

oil film covered largest area when oil spill happened at high tide moment under the dominant wind. The

predicted results could provide technical support for the oil spill emergency decision-making and its damage

assessment.

1 INTRODUCTION

Over the past few decades, with the rapid

development of the global marine economy, many

oil spill accidents have frequently occurred in the

sea. Marine oil spill can significantly impact the

coastal and estuarine environment, which cause

damage to the ecosystem, beaches, coastal wetlands,

fisheries and water supplies(Wang et al., 2008;

Griggs, 2011). Recently, scientific studies on marine

oil spill prediction techniques play a key role to

ensure the emergency plans can be implement

successfully (Li et al., 2017). In the past two decades,

some oil spill simulation models have been

developed and the technology in oil spill model has

been reviewed by researchers(Wang and Shen, 2010;

Liu and Sun, 2009). Some mature oil spill models

such as OILMAP, OSIS, OSCAR, MOTHY have

been widely adopted in the oil spill prediction and

response for the coastal areas (Zhou and He, 2018;

Reed et al., 1999). The study on simulation of oil

spill in China began in the 1980s, which was

successfully applied in Pearl River Estuary(Xiong et

al., 2005), Yangtze River Estuary(Yang et al., 2013),

Bohai Bay(Zhang and Wu, 1998), Jiaozhou Bay(Lou

et al., 2001) and Meizhou Bay(Zhao et al., 2011).

There are many numerical studies on oil spill

behavior in the offshore and estuary waters, but

there are only a few reports on numerical

simulations of oil spills in the sea near islands. The

MIKE spill analysis (MIKE SA) module in this

study was used to simulate oil spills and applied to

the sea areas around Nanri Island to predict the

impact of oil spills under different weather

conditions. The predicted results could provide

technical support for the oil spill emergency

decision-making and its damage assessment, which

may reduce the impact of the oil spill accident on the

marine environment and improve the emergency

capacity for environmental risk management.

2 THE MIKE SA MODEL

The MIKE SA module uses the "oil particle"

approach to simulate the spatiotemporal behavior of

oil spills in the sea. Based on the Lagrangian

theory(Chao et al., 2001), the model predicts the

weathing of oil particles over time by predicting

drift, diffusion, turbulent diffusion (fluid and wind

field effects), evaporation, emulsification, and

126

Wang, C., Jiang, S., Guo, Z. and Li, Q.

Numerical Simulation of Oil Spill in Nanri Island Channel Based on the MIKE Spill Analysis Model.

In Proceedings of the International Workshop on Environment and Geoscience (IWEG 2018), pages 126-131

ISBN: 978-989-758-342-1

dissolution of oil particles in the sea, simulates

location, degree and scope of influence, thickness of

oil film. In addition, the model has a complete pre-

and post-processing module that can quickly process

the results file to service decision-making system.

The model has had many successful application

cases (Xu, 2011; Jiang, 2007) around the world.

The oil spill processes of MIKE SA module,

mainly includes advection, horizontal turbulent

diffusion and expansion processes.

2.1 Advection Process

Flow and wind stress are the main forces that lead to

the drift of oil particles. The advection velocity of

each grid point (

)can be computed as:

+⋅=

Where,

is the wind velocity at 10 m above

the water surface (m/s);

is the wind drift factor,

usually abopted as 0.03~0.04;

is the surface

water current velocity, which can be obtained from

the 3-D turbulence tidal model (Chao, 1999).

2.2 Horizontal Turbulent Diffusion

The turbulent diffusive transport is normally

calculated by a random walk procedure. Based on

Al-Rabeh et al.’s study (Al-Rabeh et al., 1989), the

distance that any oil particle travels by horizontal

diffusion is:

tDRS

∇⋅

−

][

where

][

−

is the random number in the

interval [-1,1];

is the horizontal diffusion

cofficient and

∇ is the time step (s).

2.3 Spreading on the Water Surface

Spreading is the horizontal expansion of oil slick

due to gravity, inertia, viscous and surface tension

forces. A modified Fay-type spreading equation is as

follow:

⎟

⎠

⎞

⎜

⎝

⎛

⋅=

(1)

Where A is the area of the oil slick (m

); ܭ

௔

is a

coefficient; ܸ is the oil volumn; t is time in seconds.

3 HYDRODYNAMIC MODEL

AND MODEL VALIDATION

3.1 Hydrodynamic Model

In this paper, MIKE model was selected as the

hydrodynamic forecast component around Nanri

Island area. The simulated area include Meizhou

Bay, Pinghai Bay and Xinghua Bay, with the south

boundary reaching N24˚52’and the east boundary up

to E119˚ 36’ (Figure 1). In this model, an

unstructured triangular was created (Figure 2). The

grid resolution in most of computing, such as coastal

areas, and harbors was refined to 50m, while the grid

resolution was set to 1.5km in the open boundary.

The tide forcing at open boundaries consisted of

tidal elevations and barotropic velocities for 8 major

tide constituents, which are obtained from the

Oregon State University Tidal Data Inversion

software.

Figure 1: Locations of oil spill and sensitive objects in the

sea area around Nanri island.

390000 410000 430000 450000

2760000

2780000

2800000

2820000

Nanri

Island

Pinghai

Fengwei

Jiangyin

Island

Xinghua Bay

Meizhou

Bay

cultivation area

oil spill point

cultivation area

Marine

protected

area

Marine

protected

area

observation station

Numerical Simulation of Oil Spill in Nanri Island Channel Based on the MIKE Spill Analysis Model

127

Figure 2: The grid configuration and the bathymetry of the

simulated area.

3.2 Validation of Hydrodynamic Model

In this study, observation from one tidal station as

tidal elevations and three current stations including

the surface current velocities and directions were

adopted to validate the model results (Figure 1). The

tidal elevation comparison between observation and

the model simulated outputs was shown in Figure 3.

The tidal elevations from the model were in good

agreement with the observed data. The tidal

elevations were thus well predicted.

Figure 3: The tidal elevation comparison (point:

observation; line: model outputs).

As shown in Figure 4, the surface current

velocities and direction from the numerical model

were in good agreement at different stations, which

showed that the model could produce reliable

prediction of the current velocity and direction.

3.3 Surface Water Currents

The simulated surface water current near Nanri

Island at different times was showed in Figure 5.

The essential formation of water current was

reversing currents, and the direction changes of

water current occurred at the time of high or low tide.

The maximum current velocity rapidly generated

when the rate of tidal level rise or ebb reached

maximum. The tidal currents in calculated area were

typical reciprocation currents in a tidal cycle and the

tidal flats changed obviously along the tidal cycle.

4 ACCIDENTAL OIL SPILL

IMPACT PREDICTION IN THE

SEA AREA AROUND NANRI

ISLAND

4.1 Oil Spill Parameter

The assumed location of oil spill in this study is

24.47°N, 118.09°E (Figure 1), which was the

intersection of the Nanri Island channel and the

fishermen’s route, where oil spills occured

frequently in the past. The type of oil spilled was

fuel oil with a specific gravity of 920 kg/m

. The

designed oil spill volume was 10 tons (transient oil

spill), which was represented by 1000 “oil particles”

in the model. The wind speed was 4.5m/s and the

perennial dominant wind direction was northeast for

the model. For the time of oil spill, 4 kinds of

situations were selected: high tide moment, low tide

moment, ebb tide moment and flood tide moment.

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

1 2 3 4 5 6 7 8 9 101112 131415161718192021 2223242526 272829303132333435 3637 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61

IWEG 2018 - International Workshop on Environment and Geoscience

128

(a)1#

(b)2#

Figure 4: The current velocities (left) and direction (right) comparison form the model and observations

at different station (point: observation; line: model outputs).

(

)

h tide time

(

)

flood tide time

(d) ebb tide time

Figure 5: The simulated surface water currents near Nanri Island at different times.

0.00

0.20

0.40

0.60

0.80

1 3 5 7 9 11131517192123 25272931333537 39414345474951 5355575961

180

270

360

1 3 5 7 9 1113151719212325272931333537394143454749515355575961

0.00

0.20

0.40

0.60

0.80

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61

180

270

360

1 3 5 7 9 1113151719212325272931333537394143454749515355575961

0.00

0.20

0.40

0.60

0.80

135791113151719212325272931333537394143454749515355575961

180

270

360

1 3 5 7 9 1113 1517 1921 2325 2729 31 3335 3739 4143 45474951 53 55 57 5961

Numerical Simulation of Oil Spill in Nanri Island Channel Based on the MIKE Spill Analysis Model

129

Table 1: Influence area of oil concentration increment over 48 h under northeast wind conditions (km

Concentration (mg/L) High tide moments Flood tide moments Low tide moments Ebb tide moments

≥0.05mg/L 190.81 176.49 104.83 159.55

≥0.3 mg/L 142.95 135.36 84.68 89.07

≥0.5 mg/L 117.71 109.63 75.28 67.12

Figure 6a: Influence scope after oil spill

over 48 h at high tide moments under

northeast conditions.

Figure 6b: Influence scope after oil spill over

48 h at flood tide moments under northeast

conditions.

Figure 6c: Influence scope after oil spill

over 48 h at low tide moments under

perennial dominant wind.

Figure 6d: Influence scope after oil spill over

48 h at ebb tide moments under northeast

conditions.

4.2 Oil Spill Impact Prediction

After oil spills into the sea, advection, diffusion,

evaporation and other processes take place under the

combined effects of ocean hydrodynamic

environment and atmospheric environment. In this

study, the simulation time was 48h, and the oil spill

risk prediction included four schemes. Under the

conditions of northeast wind, the 48 hour impact

scope of oil spill leakage at 4 different tides were

shown in Figure 6 (≥0.05mg/L). The scope of

impact under different concentration increments

were shown in Table 1. The total impact areas of oil

spills in four tidal were 190.81 km

, 176.49 km

104.83 km

and 159.55 km

respectively.

4 CONCLUSIONS

Based on the MIKE SA model, the oil spill

prediction model for the sea area around Nanri

Island was established. The drift path and impact

degree of oil spills under the prevailing wind

direction were well simulated.

390000 410000 430000 450000

2760000

2780000

2800000

2820000

Nanri

Island

Pinghai

Fengwei

Jiangyin

Island

Xinghua Bay

Meizhou

Bay

mg/L

0.05

0.3

0.5

cultivation area

Marine

protected

area

Marine

protected

area

390000 410000 430000 450000

2760000

2780000

2800000

2820000

Nanri

Island

Pinghai

Fengwei

Jiangyin

Island

Xinghua Bay

Meizhou

Bay

mg/L

0.05

0.3

0.5

cultivat ion area

cultivation area

Marine

protected

area

Marine

protected

area

390000 410000 430000 450000

2760000

2780000

2800000

2820000

Nanri

Island

Pinghai

Fengwei

Jiangyin

Island

Xinghua Bay

Meizhou

Bay

mg/L

0.05

0.3

0.5

cultivation area

Marine

protected

area

Marine

protected

area

390000 410000 430000 450000

2760000

2780000

2800000

2820000

Nanri

Island

Pinghai

Fengwei

Jiangyin

Island

Xinghua Bay

Meizhou

Bay

mg/L

0.05

0.3

0.5

cultivation area

Marine

protected

area

Marine

protected

area

IWEG 2018 - International Workshop on Environment and Geoscience

130

The simulation results showed that the drifting

process of oil spills was mainly affected by the tide

and wind, and the tide played a leading role. Under

the prevailing wind direction (Northeast wind)

conditions, the oil film moves southwestwards under

the influence of tide and wind. The impact of oil

spillage at the time of high tide was the largest, and

the sea areas that exceed one (or two), three and four

water quality standards were 190.81, 142.95 and

11.71 km

respectively. Although the simulation

model in this study adopted long-term statistical

meteorological conditions, the prediction result still

provided effective and referable oil spill behavior

and technical support for the oil spill emergency

decision-making to the marine environmental

management department administration, which can

reduce the impact of oil spill accidents on the marine

environment and improve the emergency capacity

construction of environmental risk management

ACKNOWLEDGEMENT

The research was funded by the National Natural

Science Foundation of China (Grant No.41406121).

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Numerical Simulation of Oil Spill in Nanri Island Channel Based on the MIKE Spill Analysis Model

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