Fluid mechanics is a sub-discipline of physics that focuses on all fluidic matter, which includes liquids and gases, and the forces involved. A fluid can be defined as a substance that does not have a fixed shape, and it is deformed continuously by applied, tangential forces. There are two principal categories of fluid mechanics: fluid statics and fluid dynamics. These two categories explore both fluids at rest and moving fluids, respectively.

Before we consider modern fluid mechanics, it is important to know how this field, along with hydraulics, has developed over the course of history. More than 2000 years ago, Greece, Egypt and Mesopotamia began constructing water canals and channels – hence engineers had to study the motion of water to develop plans to construct the canals. This led to the invention of methods of storage for water, and the invention of ships as a means of transportation. However, it was not until the period of Leonardo da Vinci that hydraulics, as a science, was properly studied. In Leonardo’s work, many passages describing the flow of water, the destructive forces of water, buoyancy, and hydraulic machinery are mentioned. He also created a sketch showing the movement of water around an object, and the subsequent formation of vortices. After the times of Leonardo, many scientists found interest in the mechanics of fluids – inventing modern hydraulic machinery and improving the maritime industry.

Fluid statics, also known as hydrostatics, is one of the chief categories of fluid mechanics. Contrary to fluid dynamics, it is the study of fluids at rest, and at equilibrium. According to current laws in fluid mechanics, a fluid will not be at rest if there is shear stress present – shear stress being the force per unit area, where the stress is parallel to the surface of the fluid. Buoyancy is an example of the forces studied in hydrostatics, being defined as the vertical force that is equal in magnitude but opposite in direction of the weight of the fluid. This concept is taught in the chapter of Forces during our Physics tuition classes, and it is particularly used for the designing of floatation devices and boats. The study of fluid statics is also useful for a variety of other fields, such as medicine and geophysics.

Fluid dynamics, also called hydrodynamics, is the second main category of fluid mechanics. It is defines as the study of fluids in motion, such as the motion of water around an object. Hydrodynamics has numerous applications, and is such a large discipline that it contains several branches (e.g. aerodynamics). Additionally, it is used to calculate pressure, viscosity, and mass flow. Equations, known as the Navier-Stokes equations, are used to perform similar calculations, relating to the motion of fluids. Currently, hydrodynamics is a discipline of intense, active research – such that cash rewards are offered to those who can solve existing problems.