Fluid Mechanics and Fluid Dynamics

Fluid mechanics is one of the oldest and broadest fields of engineering. It deals with the properties and behavior of fluids, i.e., liquids and gases at rest (fluid statics) or in motion (fluid dynamics). Because of their ability to flow, liquids and gases have many properties in common not shared by solids. The study of fluids in motion, or fluid dynamics, makes up the larger part of fluid mechanics. Branches of fluid dynamics include hydrodynamics (study of liquids in motion) and aerodynamics (study of gases in motion) as well as vortex dynamics, gas dynamics, computational fluid dynamics (CFD), convection heat transfer, flows of turbo machinery, acoustics, bio-fluids, physical oceanography, atmospheric dynamics, wind engineering, and the dynamics of two-phase flows. Modern design of aircraft, spacecraft, automobiles, ships, land and marine structures, power and propulsion systems, or heat exchangers relies on a clear understanding of the relevant fluid mechanics.

CFD is a computational technology that enables the user to study the dynamics of things that flow. Using CFD, a computational model is built that represents the system or device being studied. Then, the fluid flow physics is applied to this virtual model, and the software generates a prediction of the flow about or inside the body being studied. With correct numerical simulation of the flow field, fluid forces and movements can be calculated and used for practical engineering purposes such as aircraft design.

CFD uses high-speed computers and numerical methods to seek approximate solutions to the mathematical equations that describe fluid flow. It allows designers to predict quantitatively what will happen when fluids flow and has, to some extent, replaced the use of wind tunnels for modeling of the behavior of fluids. Such an approach is useful because the complexity of fluid motion and its governing mathematical equations often defy more traditional techniques.