Fluid mechanics is the study of how fluids–liquids and gases–behave at rest and in motion. Scientists and engineers use fluid mechanics to understand how a fluid affects an object moving through it, a structure covered by it, or a pipe or channel through which it flows. Other uses include analyses of river flows, ocean waves, and weather systems. The main branches of fluid mechanics are (1) fluid statics, (2) external fluid mechanics, and (3) internal fluid mechanics.
Fluid statics
describes the balance between gravity and pressure in fluids at rest. An important law of fluid statics is Archimedes’ principle, which explains the forces that keep ships buoyant, (able to float) (see Hydraulics (Laws of hydrostatics) ). Fluid statics helps engineers design ships, submarines, and dams.
External fluid mechanics
is the study of forces acting on a stationary object in a moving fluid–a skyscraper in the wind, for example–or a moving object in a stationary fluid, such as an airplane flying through the air. Aerodynamics deals with forces produced by air and other gases; hydrodynamics, with forces produced by water and other liquids.
Internal fluid mechanics
describes fluid flow through pipes or tubes. Engineers use internal fluid mechanics in the design of pipelines for the transport of oil or water. They also apply it to the design of such machinery as fans, pumps, turbines, and compressors.
