3.4.2.2.2 Particle trajectories at various angles
For computational convenience, the plastic particles are
considered to have spherical shape. As stated above,
their density is set to 1000 kg/m³. The particles are characterized
by their diameter and are always injected at a
distance of 12.5 m from the boom. As mentioned earlier,
in order to simplify the model, these simulations are done
considering the booms to be rigid and immovable. Apart
from neglecting any turbulence caused due to the winds
and waves in a realistic ocean environment, the particleparticle
interactions and the back action of the particles
on the fluid are ignored.
Figures 3.43 and 3.44 show the particle trajectories for
particles of diameter 3 mm. One hundred particles are
injected, distributed randomly in the inlet region down
to a depth of 4 m. During average weather conditions the
majority of the floating plastics in the ocean environment
are found to be distributed within this depth (Chapter
2.3).
When comparing the results for the tilting angles of 10°
and 30°, it becomes clear that the particle velocities
along the boom increase with increasing angle. At a boom
angle of 10°, there are some particles that escape the
boom and travel underneath, not able to stay on the surface
by withstanding the ocean’s drag force, whereas all
100 particle trajectories seem to travel along the boom,
indicating that the catch probability is 1 in the flow field
with barrier angle 30°. This catch probability is quantified
in the following paragraph.