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# Technical Terms in Fluid Mechanics

## Some commonly used technical terms in fluid mechanics.

### Acoustic theory

• Relating to mathematical description of sound waves
• Acoustical Engineering - Explains to architects and engineers the basic science of acoustics. Introduction to sound, decibel and propagation of sound. Calculate decibels, reduce noise in HVAC systems, sound levels ..

### Aerodynamics

• Aerodynamics is the study of the flow of gases.
• The Ideal Gas Law - For a perfect or ideal gas the change in density is directly related to the change in temperature and pressure as expressed in the Ideal Gas Law.

### Aeronautics

• Aeronautics is the mathematics and mechanics of flying objects, in particular airplanes.

### Boundary layer

• The boundary layer is the layer of fluid in the immediate vicinity of a bounding surface.
• Dynamic, Absolute and Kinematic Viscosity - An introduction to dynamic, absolute and kinematic viscosity and how to convert between CentiStokes (cSt), CentiPoises (cP), Saybolt Universal Seconds (SSU) and degree Engler.

### Compressible flow

• In a compressible flow the compressibility of the fluid must be taken into account.
• The Ideal Gas Law - For a perfect or ideal gas the change in density is directly related to the change in temperature and pressure as expressed in the Ideal Gas Law.
• Properties of Gas Mixtures - Special care must be taken for gas mixtures when using the ideal gas law, calculating the mass, the individual gas constant or the density.
• The Individual and Universal Gas Constant - The Individual and Universal Gas Constant is common in fluid mechanics and thermodynamics.

### Coanda effect

• The Coanda Effect is the tendency of a stream of fluid to stay attached to a convex surface, rather than follow a straight line in its original direction.

### Conservation laws

• The conservation laws states that particular measurable properties of an isolated physical system does not change as the system evolves.
• conservation of energy (including mass)
• Fluid Mechanics and Conservation of Mass - The law of conservation of mass states that mass can neither be created or destroyed.

### Euler equations

• In fluid dynamics, the Euler equations govern the motion of a compressible, inviscid fluid. They correspond to the Navier-Stokes equations with zero viscosity, although they are usually written in the form shown here because this emphasizes the fact that they directly represent conservation of mass, momentum, and energy.

### Euler Number

• The Euler Number - An introduction to and a definition of the Euler Number.

### Flow measurement

• Fluid Flow-meters - Tools and information regarding fluid flowmeters.
• Fluid Flow Measurement - An introduction to different types of fluid flowmeters - Orifices, Venturies, Nozzles, Rotameters, Pitot Tubes, Calorimetrics, Turbine, Vortex, Electromagnetic, Doppler, Ultrasonic, Thermal, Coriolis.

### Fluids

• The Bernoulli Equation - A statement of the conservation of energy in a form useful for solving problems involving fluids. For a non-viscous, incompressible fluid in steady flow, the sum of pressure, potential and kinetic energies per unit volume is constant at any point.
• Equations in Fluid Mechanics - Continuity, Euler, Bernoulli, Dynamic and Total Pressure
• Laminar, Transitional or Turbulent Flow - It is important to know if the fluid flow is laminar, transitional or turbulent when calculating heat transfer or pressure and head loss.

### Froude number

• The Froude Number - An introduction to and a definition of the Froude Number.

### Gas

• The Ideal Gas Law - For a perfect or ideal gas the change in density is directly related to the change in temperature and pressure as expressed in the Ideal Gas Law.
• Properties of Gas Mixtures - Special care must be taken for gas mixtures when using the ideal gas law, calculating the mass, the individual gas constant or the density.
• The Individual and Universal Gas Constant - The Individual and Universal Gas Constant is common in fluid mechanics and thermodynamics.

### Hydraulics

• Hydraulics is a branch of science and engineering concerned with the use of liquids to perform mechanical tasks.

### Hydrodynamics

• Hydrodynamics is the fluid dynamics applied to liquids, such as water, alcohol, and oil.

### Ideal Gas

• The Ideal Gas Law - For a perfect or ideal gas the change in density is directly related to the change in temperature and pressure as expressed in the Ideal Gas Law.
• Properties of Gas Mixtures - Special care must be taken for gas mixtures when using the ideal gas law, calculating the mass, the individual gas constant or the density.
• The Individual and Universal Gas Constant - The Individual and Universal Gas Constant is common in fluid mechanics and thermodynamics.

### Knudsen number

• Used by modelers who wish to non dimensionless speed

### Laplace's equation

• Describes the behavior of gravitational, electric, and fluid potentials.

### Lift (force)

• Lift consists of the sum of all the aerodynamic forces normal to the direction of the external airflow.

### Mach number

• When an object travels through a medium, then its Mach number is the ratio of the object's speed to the speed of sound in that medium.
• The Mach Number - An introduction to and a definition of the Mach Number.

### Navier-Stokes Equations

• The motion of a non-turbulent, Newtonian fluid is governed by the Navier-Stokes equation. The equation can be used to model turbulent flow, where the fluid parameters are interpreted as time-averaged values.

### Newtonian Fluid

• A fluid is Newtonian if viscosity is constant applied to shear force.
• Dynamic, Absolute and Kinematic Viscosity - An introduction to dynamic, absolute and kinematic viscosity and how to convert between CentiStokes (cSt), CentiPoises (cP), Saybolt Universal Seconds (SSU) and degree Engler.

### Non-Newtonian fluid

• Non-Newtonian fluid viscosity changes with the applied shear force.

### Prandtl number

• Prandtl Number is a Dimensionless number approximating the ratio of momentum diffusivity and thermal diffusivity.

### Pressure

• What is Pressure? - An introduction to pressure, a definition and a presentation of common units as psi and Pa, and the relationship between them.

### Richardson number

• A dimensionless number that expresses the ratio of potential to kinetic energy.

### Reynolds number

• The Reynolds number is used for determine whether a flow is laminar or turbulent.
• The Reynolds Number - An introduction to and a definition of the dimensionless Reynold's Number.
• Reynold's Number in Water Tubes - Reynolds Number in tubes at different dimensions transporting clean cold water.

### Shock wave

• A shock wave is a strong pressure wave produced by explosions or other phenomena that create violent changes in pressure.

### Sound barrier

• The sound barrier is the apparent physical boundary stopping large objects from becoming supersonic.
• The Mach Number - An introduction to and a definition of the Mach Number.
• Speed of Sound - Speed of sound in air, fluids and solids. Formulas and values for different materials.

### Streamline - Stream function

• a streamline is the path that an imaginary particle would follow if it was embedded in the flow.

### Strouhal number

• The Strouhal number is a quantity describing oscillating flow mechanisms.
• The Strouhal Number - An introduction to and a definition of the Strouhal Number.

### Supersonic Flow

• Flow with speed above the speed of sound, 1,225 km/h at sea level, is said to be supersonic.
• The Mach Number - An introduction to and a definition of the Mach Number.
• Speed of Sound - Speed of sound in air, fluids and solids. Formulas and values for different materials.

### Surface tension

• Surface tension is a force within the surface layer of a liquid that causes the layer to behave as an elastic sheet.

### Transonic

• Flow with speed at velocities just below and above the speed of sound is said to be transonic.
• The Mach Number - An introduction to and a definition of the Mach Number.

### Vapor pressure

• For a particular substance at any given temperature there is a pressure at which the vapor of that substance is in equilibrium with its liquid or solid forms.

### Velocity

• The Bernoulli Equation - A statement of the conservation of energy in a form useful for solving problems involving fluids. For a non-viscous, incompressible fluid in steady flow, the sum of pressure, potential and kinetic energies per unit volume is constant at any point.

### Venturi

• A Venturi is a system for speeding the flow of the fluid, by constricting it in a cone-shaped tube.

### Vorticity

• Vorticity is defined as the circulation per unit area at a point in the flow field.
• The Vortex Flow meter Principle - An introduction to the vortex flowmeter principle.

### Wave drag

• Wave drag refer to a sudden and very powerful drag that appears on aircrafts flying at high-subsonic speeds.

### Weber Number

• The Weber Number - An introduction to and a definition of the Weber Number.

## Related Topics

• ### Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
• ### Hydraulics and Pneumatics

Hydraulic and pneumatic systems - fluids, forces, pumps and pistons.

## Related Documents

• ### Conservation of Mass

The Law of Conservation of Mass states that mass can neither be created or destroyed.
• ### Flow Coefficient Cv vs. Flow Factor Kv

Comparing flow coefficients Cv to flow factors Kv.
• ### Fluid Flow - Equation of Continuity

The Equation of Continuity is a statement of mass conservation.
• ### Froude Number

Introduction to the Froude Number.
• ### Strouhal Number

Introduction to the Strouhal Number
• ### Weber Number

The Weber Number may be useful when analyzing fluid flows where there is an interface between two different fluids.

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## Citation

• The Engineering ToolBox (2003). Technical Terms in Fluid Mechanics. [online] Available at: https://www.engineeringtoolbox.com/technical-terms-fluid-mechanics-d_181.html [Accessed Day Month Year].

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9.27.11