Structural Analysis of Oil-Spill Booms - Mathematical Modelling and Numerical Simulation of Oil Pollution Problems - page 155

the current direction is more close to the normal direction of the curtain. This effect
induces more stress in the curtain.
Pneumatic Boat
During favourable weather condition, the relative position of the small boat with the
floating boom can be approximatively constant. The operational mode of the GPS
position measure at a boom connection is shown on the following Fig. 7.9 .
The sea situation allows a valuable number of 7 satellites for GPS tracking. The
constant distance between the small boat and the boom permits to construct the
boom geometry by using the boat positions. These boat and boom positions are
shown on the following Fig. 7.10 . The buoy position is indicated on Fig. 7.10 .The
coordinates system used is “Lambert I Nord”. A 27min period of time has been
necessary December 4 for GPS measurements between 15h39 and 16h06.
A screenshot of the ADCP current profiler installed on the small boat permits to
show the following Fig. 7.11 . Figure 7.11 gives the vertical current profiles observed
during different runs of the boat around the boom.
We observe two white zones near the sea surface and sea bottom. These disad-
vantages are sometimes encountered with the ADCP measure. We obtained white
zones at mid-depth which indicated measure with lack of consistency. These ones
can be interpreted by the presence of phytoplankton going suspended or a large tem-
perature or salinity gradient between river flow and tide flow. Another possibility is
the presence of sediment in suspension. We notice that this effect is only present for
deep water.
Fig. 7.9 Boom geometry measurement with GPS