Technical Terms in Fluid Mechanics

Some commonly used technical terms in fluid mechanics

TermCategoryDescription
Acoustic theorySound & WavesRelating to mathematical description of sound waves
AerodynamicsFlow of GasesThe study of the flow of gases
AeronauticsFlight MechanicsThe mathematics and mechanics of flying objects, in particular airplanes
Bernoulli's equationFluid DynamicsDescribes the behavior of moving fluids along a streamline
Boundary layerFluid MechanicsThe layer of fluid in the immediate vicinity of a bounding surface
CavitationFluid PhenomenaFormation of vapor bubbles in liquid flow, related to Net Positive Suction Head (NPSH)
Compressible flowFlow TypesFlow where the compressibility of the fluid must be taken into account
Coanda effectFluid BehaviorThe tendency of a stream of fluid to stay attached to a convex surface
Conservation lawsFundamental PrinciplesParticular measurable properties of an isolated physical system do not change as the system evolves
Darcy-Weisbach EquationPressure LossEquation for pressure loss and head loss due to friction in ducts and tubes
DensityFluid PropertiesMass per unit volume of a fluid
Euler equationsGoverning EquationsGovern the motion of a compressible, inviscid fluid, representing conservation of mass, momentum, and energy
Euler NumberDimensionless NumbersA dimensionless number in fluid mechanics
Flow Coefficient (Cv, Kv)Flow MeasurementCoefficients used to characterize flow through control valves
Flow measurementInstrumentationTools and methods for measuring fluid flow rates
FluidsGeneral Fluid MechanicsSubstances that flow and conform to the shape of their containers
Froude numberDimensionless NumbersA dimensionless number in fluid mechanics
GasFluid TypesA state of matter characterized by low density and high compressibility
HydraulicsEngineering ApplicationsScience and engineering concerned with the use of liquids to perform mechanical tasks
HydrodynamicsFluid DynamicsFluid dynamics applied to liquids, such as water, alcohol, and oil
Ideal GasGas LawsA gas that obeys the ideal gas law
Knudsen numberDimensionless NumbersUsed to determine the validity of continuum mechanics
Laminar FlowFlow TypesFlow characterized by smooth, parallel layers with no mixing between layers
Laplace's equationMathematical PhysicsDescribes the behavior of gravitational, electric, and fluid potentials
Lift (force)AerodynamicsSum of all aerodynamic forces normal to the direction of external airflow
LiquidsFluid TypesA state of matter with definite volume but no definite shape
Mach numberDimensionless NumbersRatio of an object's speed to the speed of sound in that medium
Navier-Stokes EquationsGoverning EquationsEquations governing the motion of a non-turbulent, Newtonian fluid
Newtonian FluidFluid TypesA fluid with constant viscosity regardless of applied shear force
Non-Newtonian fluidFluid TypesA fluid whose viscosity changes with the applied shear force
Prandtl numberDimensionless NumbersRatio of momentum diffusivity to thermal diffusivity
PressureFluid PropertiesForce per unit area exerted by a fluid
Reynolds NumberDimensionless NumbersUsed to determine whether a flow is laminar or turbulent
Richardson numberDimensionless NumbersExpresses the ratio of potential to kinetic energy
Shock waveWave PhenomenaA strong pressure wave produced by explosions or violent pressure changes
Sound barrierSpeed PhenomenaThe apparent physical boundary stopping large objects from becoming supersonic
Streamline - Stream functionFlow VisualizationThe path that an imaginary particle would follow if embedded in the flow
Strouhal numberDimensionless NumbersDescribes oscillating flow mechanisms
Supersonic FlowFlow TypesFlow with speed above the speed of sound
Surface tensionFluid PropertiesForce within the surface layer of a liquid causing it to behave as an elastic sheet
TransonicFlow TypesFlow with speed at velocities just below and above the speed of sound
Turbulent Flow - TurbulenceFlow TypesFlow characterized by chaotic, irregular fluid motion
Vapor pressureFluid PropertiesPressure at which the vapor of a substance is in equilibrium with its liquid or solid forms
VelocityFlow PropertiesSpeed and direction of fluid motion
VenturiFlow ControlA system for speeding the flow of a fluid by constricting it in a cone-shaped tube
ViscosityFluid PropertiesMeasure of a fluid's resistance to flow
VorticityFlow CharacteristicsCirculation per unit area at a point in the flow field
Wave dragAerodynamic PhenomenaSudden and powerful drag appearing on aircraft flying at high-subsonic speeds
Weber NumberDimensionless NumbersA dimensionless number in fluid mechanics