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|