CHARACTERISTICS

DESCRIPTION

Identification

Mu- Slick
Model originator: MUMM
Model operator: S.Scory

Scope

The Mu-Slick model is designed to forecast the fate (transport, spreading and ageing) of a spill of oil or of a floating chemical at sea

Conceptual background

The transport of the slick is modelled by the transport of the centre of mass with as velocity the sum of the water current speed and the wind induced surface speed.

The spreading is computed assuming that the slick remains circular. The radius is the solution of the equilibrium between gravity, surface tension, inertia, interfacial and internal viscous force.

The ageing of the slick takes into account the processes of evaporation, emulsification, direct sea-air interaction, dispersion and dissolution. The variations of the physical characteristics due to the ageing processes are also parameterised and the impact of some combating actions is also incorporated.

Inputs

To be run, the model needs on input,

— the spill coordinates

— the spilled volume

— the bathymetry (coastline)

— the fields of water current speed and of wind speed in the area of interest

some characteristics of the oil or of the chemical (i.e. specific mass, surface tension, molecular weight, vapour pressure, cinematic viscosity, emulsification capability and evaporable fraction).

Geographical coverage

The model works inside the geographical area covered by the hydrodynamic model to which it is linked

Outputs

The model provides hourly information about the slick position, the slick shape and the characteristics of the oil

Validation

The trajectories computed by the model are strongly dependent on the reliability of the water current and wind fields available. Results obtained within the frame of real incidents, with the currents computed by Mu-Storm model and the meteorological forecasts provided by the U.K. Meteorological Office have been very satisfactory.

Concerning the ageing processes, no in-depth validation of the model results has been done possible so far.

Present field of application

The model coupled to the Mu-Storm model is ready to forecast the fate of a spill occurring anywhere in the North Sea, 24 hours a day.

Possible complementary use

The transport module of Mu-slick could can also be used to compute estimate the drift of any floating device.

Present limitations, future needs and possible development

The model is essentially limited by the assumptions made concerning the shape of the slick. The model must be considered as being able to provide first order estimates.

On-going developments: The model is currently being expanded to a "particle"-version (Mu-slicklets, which models the oil by a lot of little slicks.).

Reference of representative publication

S.Scory, 1982, Etude du déplacement et de l'étalement d'une nappe d'hydrocarbures déversée en mer, sous l'effet du vent, des courants et de la houle. Travail de fin d'études présenté à la Faculté de Sciences appliquées de l'Université de Liège, Belgique, 147 p.

S.Scory, 1984, Oil spill modelling. Lecture given at the University of Liège, Intensive course on modelling and management of marine systems, September 3-22, 1984