* Bejan number, numbers in thermodynamics and fluid mechanics

The study of fluids is fluid mechanics, which is subdivided into fluid dynamics and fluid statics depending on whether the fluid is in motion.

In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow — the natural science of fluids ( liquids and gases ) in motion.

Arrow fletches are a type of fin. A fin is a surface used for stability and / or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, ( in other words, a foil ( fluid mechanics )).

* circulation in fluid mechanics

* 2005 – Timoshenko Medal, American Society of Mechanical Engineers, " for seminal contributions to nearly every area of solid and fluid mechanics, including fracture mechanics, turbulence, stratified flows, flames, flow in porous media, and the theory and application of intermediate asymptotics.

In scientific research, the behavior of the two fluid phases of helium-4 ( helium I and helium II ), is important to researchers studying quantum mechanics ( in particular the property of superfluidity ) and to those looking at the phenomena, such as superconductivity, that temperatures near absolute zero produce in matter.

Greek mathematician Archimedes, famous for his ideas regarding fluid mechanics and buoyancyIn the 3rd century BCE, the Greek mathematician Archimedes of Syracuse ( ( 287 BCE-212 BCE )-generally considered to be the greatest mathematician of antiquity and one of the greatest of all time-laid the foundations of hydrostatics, statics and calculated the underlying mathematics of the lever.

Since air and water are governed by similar fluid equations, albeit with vastly different levels of viscosity, density, and compressibility, the hydrofoil and airfoil create lift in identical ways ( see foil ( fluid mechanics )).

He is also renowned for his work in mechanics, fluid dynamics, optics, and astronomy.

* Foil ( fluid mechanics )

However, modern rheology typically deals with non-Newtonian fluid dynamics, so it is often considered a sub-field of continuum mechanics.

In fluid mechanics, Mach number ( or ) ( generally, sometimes or ) is a dimensionless quantity representing the speed of an object moving through air or other fluid divided by the local speed of sound.

Since Sir Isaac Newton originated the concept of viscosity, the study of liquids with strain rate dependent viscosity is also often called Non-Newtonian fluid mechanics.

Theoretical aspects of rheology are the relation of the flow / deformation behaviour of material and its internal structure ( e. g., the orientation and elongation of polymer molecules ), and the flow / deformation behaviour of materials that cannot be described by classical fluid mechanics or elasticity.

In practice, rheology is principally concerned with extending continuum mechanics to characterize flow of materials, that exhibits a combination of elastic, viscous and plastic behaviour by properly combining elasticity and ( Newtonian ) fluid mechanics.

In the case of flow through a straight pipe with a circular cross-section, at a Reynolds number below the critical value of approximately 2040 fluid motion will ultimately be laminar, whereas at larger Reynolds number the flow can be turbulent.

In particular, the Reynolds number ( which compares the effect of momentum of a fluid to the effect of viscosity ) can become very low.

The molecular transfer equations of Newton's law for fluid momentum at low Reynolds number ( Stokes flow ), Fourier's law for heat, and Fick's law for mass are very similar, since they are all linear approximations to transport of conserved quantities in a flow field.

In 1851, George Gabriel Stokes derived an expression for the frictional force ( also called drag force ) exerted on spherical objects with very small Reynolds numbers ( e. g., very small particles ) in a continuous viscous fluid by changing the small fluid-mass limit of the generally unsolvable Navier-Stokes equations:

It is generally believed that it is due to the inertia of the fluid as a whole: the culmination of time dependent and convective acceleration ; hence flows where inertial effects are small tend to be laminar ( the Reynolds number quantifies how much the flow is affected by inertia ).

Bernoulli's principle, which is a function of the velocity of the fluid, is a dominant effect for large openings and large flow rates, but since fluid flow at small scales and low speeds ( low Reynolds number ) is dominated by viscosity, Bernoulli's principle is ineffective at idle or slow running and in the very small carburetors of the smallest model engines.

* Reynolds number ( a dimensionless number describing the fluid flow regime )

For low values of the Reynolds number (< 1 ), which is true of most aerosol motion, Stokes ' law describes the force of resistance on a solid spherical particle in a fluid.

Note that whereas the Reynolds number and Grashof number are subscripted with a length scale variable, the Prandtl number contains no such length scale in its definition and is dependent only on the fluid and the fluid state.

The critical angle of attack is typically about 15 degrees, but it may vary significantly depending on the fluid, foil, and Reynolds number.

Although laminar-turbulent transition is not governed by Reynolds number, the same transition occurs if the size of the object is gradually increased, or the viscosity of the fluid is decreased, or if the density of the fluid is increased.

Although it is possible to find some particular solutions of the Navier-Stokes equations governing fluid motion, all such solutions are unstable at large Reynolds numbers.

These layers separate the fast moving jet from the external fluid, and at a certain critical Reynolds number they become unstable and break down to turbulence.

This decomposition of a flow variable into a mean value and a turbulent fluctuation was originally proposed by Osborne Reynolds in 1895, and is considered to be the beginning of the systematic mathematical analysis of turbulent flow, as a sub-field of fluid dynamics.

The velocity, blood vessel diameter, and the fluid thickness can all be related with the Reynolds Number, a dimensionless number used in fluid mechanics to characterize the flow of fluids.

In 1851, George Gabriel Stokes derived an expression, now known as Stokes ' law, for the frictional force – also called drag force – exerted on spherical objects with very small Reynolds numbers ( e. g., very small particles ) in a continuous viscous fluid.

* Reynolds stress model, for modeling turbulence in fluid dynamics

The Zed axis, which can be characterized by Reynolds Number, represents the range of fluid viscosities ( or stickiness ).

Osborne Reynolds FRS ( 23 August 1842 – 21 February 1912 ) was a prominent innovator in the understanding of fluid dynamics.

Thus, when the fluid finally does strike the object, it is forced to change its properties -- temperature, density, pressure, and Mach number -- in an extremely violent and irreversible fashion called a shock wave.

For flow of gases, to determine whether to use compressible or incompressible fluid dynamics, the Mach number of the flow is to be evaluated.

Hall effect sensors are readily available from a number of different manufacturers, and may be used in various sensors such as rotating speed sensors ( bicycle wheels, gear-teeth, automotive speedometers, electronic ignition systems ), fluid flow sensors, current sensors, and pressure sensors.

The Mach number is commonly used both with objects traveling at high speed in a fluid, and with high-speed fluid flows inside channels such as nozzles, diffusers or wind tunnels.

Mach number is useful because the fluid behaves in a similar way at the same Mach number.

Static pressure and stagnation pressure are related by the Mach number of the fluid.

In 2009, Mike Richard John Smith filed a Canadian Patent application ( Canadian Patent number: 2675044 ) indicating the screw type propeller is inefficient due to the screw type blade orientation of the propeller which when in operation for forward movement substantially moves the fluid ( for a boat the fluid is water ) sidewardly, rotationally, and rearwardly wherein moving the fluid sidewardly does not move the boat forward, thus contibuting to the inefficiency of the screw type propeller.

* Phencyclidine, a recreational drug known by a number of street names including PCP, angel dust, embalming fluid, and rocket fuel

A very small Deborah number can be obtained for a fluid with extremely small relaxation time or a very large experimental time, for example.

The concept included limiting the number of sexual partners, using prophylactics, avoiding bodily fluid exchange, and resisting the use of drugs that reduced inhibitions for high-risk sexual behavior.

A number of pathological conditions can cause an obstruction of the normal cerebrospinal fluid pulsation.

In this design the fuel is placed in a number of ( typically spherical ) elements which " float " inside the hydrogen working fluid.

* Bond number, in fluid mechanics, a dimensionless number expressing the ratio of gravitational forces to surface tension forces