KEY TERMS
| Term | Description |
|---|---|
| Fluid | A fluid is a liquid, gas, or other material that continuously deforms (flows) under an applied shear stress, or external force |
| Fluid dynamics | Fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics and hydrodynamics. |
| Atmospheric pressure | Atmospheric pressure, also known as barometric pressure, is the pressure within the atmosphere of Earth. The standard atmosphere is a unit of pressure defined as 101,325 Pa, which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi |
| Fluid flow rate | In fluid mechanics, the volumetric flow rate (also known as volume flow rate, rate of fluid flow, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes V̇). The SI unit is cubic metres per second (m3/s). |
| Gauge pressure | Gauge pressure is the pressure relative to atmospheric pressure. Gauge pressure is positive for pressures above atmospheric pressure |
| Absolute pressure | Sum of gauge pressure and atmospheric pressure |
| Acrhimedes' principle | Archimedes' principle states that a body immersed in a fluid is subjected to an upwards force equal to the weight of the displaced fluid. Buoyant force on an object equals the weight of the fluid it displaces. |
| Bernoulli's principle | Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy. |
| Buoyant force | Buoyant force is the upward force a fluid exerts on an object |
| Density | Density is the mass per unit volume of a substance or object |
| Hydrostatic equilibrium | In fluid mechanics, hydrostatic equilibrium (hydrostatic balance, hydrostasy) is the condition of a fluid or plastic solid at rest, which occurs when external forces, such as gravity, are balanced by a pressure-gradient force. |
| Idea fluid | An ideal fluid is a fluid that is incompressible and no internal resistance to flow (zero viscosity). In addition ideal fluid particles undergo no rotation about their center of mass (irrotational). |
| Laminar flow | Laminar flow is a type of flow pattern of a fluid in which all the particles are flowing in parallel lines |
| Turbulent flow | In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. |
| Pascal's law | Pascal's law is a principle in fluid mechanics given by Blaise Pascal that states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. |
| Reynolds number | The Reynolds number (Re) helps predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers flows tend to be turbulent. |
| Specific gravity | Specific gravity, or relative density , is the ratio of the density of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its denses |
| Hydraulic gradient | This is the slope of the water surface in an open channel, the slope of the water surface of the groundwater table, or the slope of the water pressure for pipes under pressure.The hydraulic gradient is the change in total head divided the distance over which the change occurs. |
| Viscosity | The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness" |
| Boundary layer | Boundary layer, in fluid mechanics, thin layer of a flowing gas or liquid in contact with a surface such as that of an airplane wing or of the inside of a pipe. The fluid in the boundary layer is subjected to shearing forces. |