Archimedes (bryozoan) Archimedes (bryozoan) Archimedes is a genus of bryozoans belonging to the family Fenestellidae. The first use of the term "Archimedes" in relation to this genus was in 1838. This genus of bryozoans is named "Archimedes" because of its corkscrew shape, in analogy to the Archimedes' screw, a type of water pump which inspired modern ship propellers. These forms are pretty common as fossils but they have been extinct since the Permian. These bryozoans lived from the Carboniferous period (Tournaisian age) to the Permian period (Leonard age) (345.3 to 268.0 Ma), when this genus became extinct. "Archimedes" is a genus of
Archimedes number Archimedes number In viscous fluid dynamics, the Archimedes number (Ar) (not to be confused with Archimedes' constant, π), named after the ancient Greek scientist Archimedes is used to determine the motion of fluids due to density differences. It is a dimensionless number defined as the ratio of external forces to internal viscous forces and has the form: where: When analyzing potentially mixed heat convection of a liquid, the Archimedes number parametrizes the relative strength of free and forced convection. When Ar » 1 natural convection dominates, i.e. less dense bodies rise and denser bodies sink, and when Ar « 1