The dynamic seaweeds respond to simulated water currents in a
realistic manner. Each leaf of a seaweed cluster is a mass-spring
chain. The springs have identical spring constants, but the distance
between mass points as well as the mass of the successive nodes
decreases from the root to the tip (thus the leaf is more flexible and
lighter towards the tip). The leaves have positive buoyancy in the
virtual water and they are subject to the simulated currents which
cause them to sway. In order to obtain computational efficiency, we
do not calculate the forces acting on the geometric surface of each
seaweed leaf, rather, we approximate the hydrodynamic force at each
mass point as 
, where 
is the fluid
viscosity defined in Eq. (
) and 
is the
aggregate fluid velocity 
at mass point i.
Fig. shows a sequence of snapshots of the swaying
motion of a seaweed cluster (the simulated water currents are as
described above). In addition, when a fish swims through or passes by
a seaweed, the leaves respond to a simulated water force generated by
the fish's body. Fig. shows how the leaves close
to the fish's body are ``pushed'' away by the simulated hydrodynamic
forces caused by the fish. The plankton are simply modeled as floating
mass points under the influence of the simulated water currents.
Figure: The seaweed responds to hydrodynamic forces produced by a passing fish.
| Xiaoyuan Tu | January 1996 |
