Abstract
This paper describes a method of computing motion in fluid and an experiment using it. Motion of an object is computed by a physical simulation environment. It is constructed of a physical engine, which processes computation of rigid body dynamics. Computation of fluid dynamics is additionally implemented to the environment so that motion in fluid is simulated faster than other computational methods. The environment read easily the three dimensional mesh data, which is commonly used by CAD systems, then computes and visualizes motion immediately. The experiment is optimizing shapes of Leonardo da Vinci's spiral wings. Parameters of the spiral wing are optimized by a particle swarm optimization (PSO) or a sequential search so that the wing flies higher under two conditions. PSO usually find better parameters than a sequential search and do about sixty times as faster as a sequential search. The environment computes virtual motion for twenty seconds in real time of one second. The shapes given by an optimization are difference each other according to the given conditions, and proper from viewpoint of fluid dynamics.
