In physics, fluid dynamics is a subdiscipline of fluid mechanics that deals with fluid flow. Fluid dynamics is one of the most important of all areas of physics. Life as we know it would not exist without fluids and without the behavior that fluids exhibit. The air we breathe and the water we drink (which makes up most of our body mass) are fluids. Fluid dynamics has many applications, including calculating forces and moments on aircraft (aerodynamics) and determining water’s mass flow rate through pipelines (hydrodynamics).
Fluid dynamics are an important part of most industrial processes, especially those involving the
transfer of heat. In nuclear reactors, the heat removal from the reactor core is accomplished by passing a liquid or gaseous coolant through the core and other regions where heat is generated. The nature and operation of the coolant system are among the most important considerations in designing a nuclear reactor.
Fluid flow in the nuclear field can be complex and is not always subject to rigorous mathematical analysis. Unlike solids, the particles of fluids move through piping and components at different velocities and are often subjected to different accelerations. The foundational axioms of fluid dynamics are the conservation laws, specifically, conservation of mass (leading to the continuity equation), conservation of linear momentum, and conservation of energy.