Limekilns Oil Spill - 18th February 2019

Following the recent oil spill at Limekilns (https://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-47290793) MTS-CFD decided to see if they could help shed any light on the source of the spill.

 

Using our expertise in Computational Fluid Dynamics (CFD) we have created a model using the open source CFD code OpenFOAM, a code widely used in academia and industry, of which we have many years' experience.

 

A summary of the modelling approach is given below:

 

1) The computational domain is the Forth estuary from Kincardine bridge to North Berwick. The study is 2D as we are mainly interested in surface flows and this should provide a reasonable engineering estimate of reality. Coriolis forces for the Earth’s rotation are included for the latitude of Edinburgh.

 

2) The currents are wind and tide driven and the tidal speed is set using the spreadsheet located at http://www.esru.strath.ac.uk/EandE/Web_sites/05-06/marine_renewables/resource/tidalcurrents.htm.

 

3) The wind speed and direction are found on-line for the days preceding the spill (https://www.timeanddate.com/weather/uk/edinburgh/historic?month=2&year=2019) and the surface water speed is set as 3% of the wind speed (https://earthscience.stackexchange.com/questions/3060/why-is-ocean-surface-velocity-around-3-of-wind-velocity), Brown J. (1991). The final voyage of the Rapaiti. A measure of surface drift velocity in relation to the surface wind. Marine Pollution Bulletin, 22, 37-40.

 

4) The first CFD study reverses the wind speed, direction and tides while releasing massless particles at Limekilns beach where the spill was discovered on the 18th Feb. Thus, effectively running time backwards to find an estimate of the location of the spill source - see animation limekilns_North_to_South.mp4.

 

5) The second study is a time-forward one with wind and tides set from around 13-hours before the spill was found on the 18th Feb. The release point for the particles is based on the source location found in the time-reverse study of point 4). See animation limekilns_South_to_North.mp4.

 

6) The second study shows the spill arriving in the Limekilns area on the 18th Feb. 2019, approximately 13 hours after release on the south shore at high tide.

 

7)  It should be noted that the outcome of point 6 could have also been achieved by releasing the oil at any point in the particle trajectory, e.g. from a ship in mid-river, 6 hours or so before the spill was discovered at Limekilns.

Limekilns North to South

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Limekilns South to North