PAJ Oil Spill Simulation Model for Japanese Waters− D e m o n s t r a−t io nFuji Research institute CorporationTakashi Fujii

O u t lin e o f O il S p ill M o d e l
As part of "Major Oil Spill Response
Programme" Petroleum Association ofJapan (PM) has developed a diffusion-drift
model of spilt oil. The outline of this model
was reported in PM Oil Spill Symposium'95. In this session, the oil spill model will
be demonstrated more in detail.
In an oil spill incident, the extent ofdamage on surrounding environment islargely depends on the initial response.
The model, therefore, was developed tosupport the preparation of an emergency
response program effective for clean-upoperation.
The model is also useful in estimating in
advance the impact of an oil spill
according to the assumed incident.

F e a t u r e s o f th e M o d e l
Since the Objectives of the model is toprovide information about the diffusion
and trajectory of spilt oil after theoutbreak of the incident, the predictive
computation is designed to be completed
in a short time. Practically, the trajectoryof spilt oil can be predicted within about 5mm; the computation requires about 15
min even for detailed prediction including
the state of oil slick diffusion.
The model, in order to be used widely bypeople other than computer specialists,
has materialized easy manipulation.
Personal computers with MS-Windows3.1
installed including a notebook type areapplicable to the model so that the model
will be of service even in a clean-up
operation field.

− 1 −The model can predict the behavior ofspilt oil on the sea in a period up to 48 hr
after spillage. The model contains basic
data including properties of crude oil andpetroleum products, and tidal currents inthe target area of sea, and predicts withenough accuracy to be effective for theclean-up operation.
We are now considering to provide more
precise prediction with the model using
newest weather forecast data.

N u m e r ic a l M o d e l
In the model, the behavior of spilt oil isdivided roughly into two main phenomenaof diffusion and drift in order to make up
numericalmodels.

In

thediffusion

phenomenon, such processes as spreading,evaporation,emulsification,

horizontaldispersion, and vertical dispersion aretaken up, and they are calculated on thebasis of Fay, Mackay, et al.'s models.
As for drift phenomenon, processes suchas tidal current, tidal residual current,
river inflow, and wind-induced current aremodeled. Data base of tidal current with amesh unit of 1 km has been prepared inthis model. Statistical data of marine wind
are provided in the model, however, theutilization of weather forecast data ispreferable to improve the accuracy ofprediction in an oil spill.

− 2 −O b je c t iv e s S e a A r e a o f th e M o d e l(E n c lo s e d A r e a o f S e a )The areas of sea, to which the model isapplicable, are coastal areas of sea, on
which coast oil refineries etc. are located.
The eight enclosed areas of sea have beenmodeled so far, including Tokyo Bay, IseBay, Osaka Bay, and Seto Inland Sea.
Seto Inland Sea, having much larger area
than others, is divided into five areas ofsea

ofHarima-nada,

Hiuchi-nada

Hiroshima Bay, Suou-nada, and Beppu
Bay. Each of the models of these areas ofsea can be used independently, and theprediction for a district covering morethan one area is also possible.

E x a m p le o f S im u la t io n(T o k y o b a y m o d e l)A typical example of simulation, which
was carried out using the model, is shownin the first place. A large-scale oil spillincident is imagined to set up thecalculation

conditions.

Assuming

that

5,000KL of Arabian Light Crude was spilt
during 5hr (1,000KL/hr) and that thespillage broke out at 12:00, March 5, 1996,
the behavior of spilt oil was predicted in aperiod up to 48 hr after spillage.
The weather conditions (direction andspeedofwind)necessaryfor

thesimulation are provided by taking theaverage values of every hour in March inTokyo Bay area of sea.

− 3 −E x a m p le o f R e s u lt s o f S im u la t io n
Since practical operations are shown in
the later demonstration, the typicalresults of simulation are shown in thissection.
First, the user interface image of themodel and the results of trajectory of anoil slick are indicated. The trajectory ofthe center of the oil slick every 2 hr after
the outbreak of the incident.
Next, the distribution of the oil slick isgiven

inadiagram.

For

easy

understanding, the results are displayed
continuously.
The oil slick is thick and spread only in anarrow range in the initial stage ofspillage, but the slick becomes thin anddiffuses into a wider area with thepassage of time. The oil slick is predicted
to drift down the south-west dominantly
by the effect of the wind.
In this model, a phenomenon is modeledin which the oil slick drifts leaving a tailbehind it on the trajectory and can beconfirmed as the results of simulation onthe display. In an actual incident, aclean-up operations including oil boom
Deployment are set up to prevent the oil
slick from diffusing into such a wide area
as predicted by the model.

− 4 −D e m o n s t r a t io n
The required specifications of a personal
computer to which the oil spill model isapplicableareasfollows.

In

this

demonstration, a notebook-type personal
computer with i486DX4(75MHz) CPU wasused.
The typical functions of the model and itsusage are demonstrated to show thepractical use of the model. A series ofprediction procedures is indicated by suchoperations as:
・ Setting up calculation conditions
・ Execution of simulation
・ Display of the results

F u t u r e T o p ic s
The following three points are indicatedas the topics of the model in future:
First, the prediction accuracy for drift isto be improved. The improvement will beattained chiefly by the verification on thebasis of drift experiments which have been
carried out since last year.
Next, the operability is to be improved sothat the results can be displayed insequence according to the progress ofcalculations. The conversion to OS such as
Windows95 which is estimated to be
widely used in near future is anothertopic.
Last, the subject of the model is to beextended from enclosed areas of sea tooceanic coastal area of sea as given in afigure.

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