head

en-noun

head (countable and uncountable, plural heads or head)

→ Japanese: ヘッド (heddo)

Sranan Tongo: ede

Aukan: ede

Saramaccan: hédi

Etymology tree
Proto-Indo-European *kap-
Proto-Indo-European *káput-
Proto-Germanic *haubudą
Old English hēafod
Middle English heed
English head
From Middle English hed, heed, heved, heaved, from Old English hēafd-, hēafod (“head; top; source, origin; chief, leader; capital”), from Proto-West Germanic *haubud, from Proto-Germanic *haubudą (“head”), from Proto-Indo-European *káput. The modern word comes from Old English oblique stem hēafd-, the expected Modern English outcome for hēafod would be *heaved (similar to the Middle English word). Doublet of cape, capo, caput, chef, chief, and Howth.
Cognate with Scots heid, hede, hevid, heved (“head”), Old English hafola (“head”), North Frisian hood (“head”), Dutch hoofd (“head”), German Haupt (“head”), Swedish huvud (“head”), Danish hoved (“head”), Icelandic höfuð (“head”), Latin caput (“head”), Sanskrit कपाल (kapāla, “skull”), Hindi कपाल (kapāl, “skull”).

頭

つぶり, tsuburi, つぃぶる, tsiburu, つぃぶるぃ, tsiburi

pää

principal operative part of a machine or tool

have one's head screwed on the right way

know one's head from a hole in the ground

run around like a chicken with its head cut off

would lose one's head if it wasn't attached

would lose one's head if it wasn't bolted on

would lose one's head if it wasn't glued on

would lose one's head if it wasn't screwed on

would lose one's head if it wasn't stuck on

would lose one's head if it wasn't tied on

would lose one's head if it weren't attached

you can't put an old head on young shoulders

you can't put a wise head on young shoulders

Let the engine build up a good head of steam.

How much head do you have at the Glens Falls feeder dam?

en:pressure and energy in fluid dynamics

(uncountable, countable) A buildup of fluid pressure, often quantified as pressure head.

The difference in elevation between two points in a column of fluid, and the resulting pressure of the fluid at the lower point.

putouskorkeus

fluid dynamics: difference in elevation in a column of fluid, and the resulting pressure

More generally, energy in a mass of fluid divided by its weight.


strake

From Middle English strake, from Old English *straca (> Anglo-Latin straca), from Proto-West Germanic *strakō, from Proto-Germanic *strakaz (“straight”). Akin to Old English streċċan (“to make straight, stretch”).

cog

(fluid dynamics) Also used more generally to regulate fluid flow in pipes or vents to prevent turbulence or vortexes.


aerodynamics

From French aérodynamique, from aero- + dynamics.

The aerodynamic properties of a particular object (typically a car).


Bernoulli effect

en-noun

Bernoulli effect (usually uncountable, plural Bernoulli effects)

Bernoulli's principle
Bernoulli's principle

(fluid dynamics) In a flowing fluid, the occurrence of what is stated by Bernoulli's principle.


Bernoulli's principle

After Swiss mathematician and physicist Daniel Bernoulli (1700-1782), who published this principle.

(fluid dynamics) The principle which 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.


cavitation

cavitation (countable and uncountable, plural cavitations)

/ˌkævɪˈteɪʃən/

(fluid dynamics) The formation, in a fluid, of vapor bubbles that rapidly collapse, especially in a rotating marine propeller or pump impeller.


bow shock

LL-Q1860 (eng)-Flame, not lame-bow shock.wav

(fluid dynamics) A shock wave formed by the bow of an object travelling at supersonic speed.


turbulence

turbulence (countable and uncountable, plural turbulences)

Borrowed from Latin turbulentia, or from turbulent + -ence.

Turbulence was everywhere, within every blade of grass, every drop of dew on a leaf, every cloud in the sky, and every star beyond. The turbulence was purposeless, but in huge quantities of purposeless turbulence, purpose took shape.

(uncountable) The state or fact of being turbulent or agitated; tempestuousness, disturbance.


hydrodynamics

(physics) The scientific study of fluids in motion.


peniche

Peniche (fluid dynamics)
Péniche (barge)

(fluid dynamics) Material inserted between a half-model, often of an airplane, and the wall of a wind tunnel.


transition point

transition point (plural transition points)

(fluid dynamics) The point in space at which fluid flow around an object changes from laminar to turbulent.


scallop theorem

scallop theorem (plural scallop theorems)

From an explanation of a principle of fluid dynamics given by E. M. Purcell.

(fluid dynamics) A theorem which states that to achieve propulsion at low Reynolds number in simple (i.e. Newtonian) fluids, a swimmer must deform in a way that is not invariant under time-reversal.


vorticity

vorticity (countable and uncountable, plural vorticities)

It might sound puzzling that the ageostrophic geopotential (or the ageostrophic pressure in z-coordinate) has no impact on the evolution of the vorticity of a quasi-geostrophic disturbance and yet it affects the perturbation kinetic energetics (not globally but locally).

2004, Zhu Xun, Li Xiaofan, Cai Ming, Observation, Theory And Modeling Of Atmospheric Variability, →ISBN, page 13:

This results from the vorticity component of shear, whereas elongated cells would further be affected by the rate of strain component.

2009 February 20, William M. Durham et al., “Disruption of Vertical Motility by Shear Triggers Formation of Thin Phytoplankton Layers”, in Science, volume 323, number 5917, →DOI, pages 1067–1070:

An extreme version of vorticity is a vortex. The vortex is a spinning, cyclonic mass of fluid, which can be observed in the rotation of water going down a drain, as well as in smoke rings, tornados and hurricanes.

2013 March 14, Frank Fish, George Lauder, “Not Just Going with the Flow”, in American Scientist, volume 101, number 2, archived from the original on 2013-05-01, page 114:

(mathematics, fluid dynamics) A property of a fluid flow related to local angular rotation; defined as the curl of the flow's velocity field.


backpressure

backpressure (countable and uncountable, plural backpressures)

(fluid dynamics) Pressure that is opposed to the flow of a fluid.


angular frequency

angular frequency (plural angular frequencies)

(physics, fluid dynamics) A scalar measure of rate of rotation


Coandă effect

Named after Romanian aerodynamics pioneer Henri Coandă, who was the first to recognize the practical application of the phenomenon in aircraft development.

The tendency of a fluid jet to be attracted to a nearby surface.


d'Alembert's paradox

Observed in 1752 by French mathematician Jean le Rond d'Alembert.

(fluid dynamics) The contradiction that, for incompressible and inviscid potential flow, the drag force is zero on a body moving with constant velocity relative to the fluid.


Darwin drift

Named after Sir Charles Galton Darwin, who proved a related theorem in 1953.

z-component of any force on the surface of the swimmer and ρ the radial co- ordinate. v D is termed the Darwin drift: by comparison, for a colloid at zero Reynolds number this quantity is infinite. The magnitude of the Darwin drift is of the order.

2016, C.N. Likos, F. Sciortino, E. Zaccarelli, Soft Matter Self-Assembly, →ISBN, page 392:

(fluid dynamics) The phenomenon by which a fluid parcel is permanently displaced after the passage of a body through a fluid – the fluid being at rest far away from the body.


stagnation point

stagnation point (plural stagnation points)

(fluid dynamics) A point in a flow field where the local velocity of the fluid is zero.


Chézy formula

Named after Antoine de Chézy, the French hydraulics engineer who devised it in 1775.

(fluid dynamics) A formula that describes the mean flow velocity of steady, turbulent open-channel flow.


computational fluid dynamics

computational fluid dynamics (uncountable)

(computing, mechanics) The study of computational algorithms to solve mathematical problems in the field of fluid dynamics.


Morison equation

Morison equation (plural Morison equations)

Named after J. R. Morison, one of the authors of a related paper in 1950.

(fluid dynamics) A semiempirical equation for the in-line force on a body in oscillatory flow, used to estimate the wave loads in the design of oil platforms and other offshore structures.


vortex shedding

von Kármán vortex street
von Kármán vortex street

(fluid dynamics) An oscillating flow that occurs when a fluid flows past a bluff body at certain velocities. Vortices are created at the back of the body and detach periodically from either side of it, forming a von Kármán vortex street.


Archimedes' principle

(fluid dynamics) A law that states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces.


Hagen-Poiseuille equation

the Hagen-Poiseuille equation (canonical)

It was experimentally derived independently by Jean Léonard Marie Poiseuille in 1838 and Gotthilf Heinrich Ludwig Hagen, and published by Poiseuille in 1840–41 and 1846.

(fluid dynamics) A physical law that gives the pressure drop in an incompressible Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section.


Gerstner wave

Discovered in 1802 by Franz Josef Gerstner.

(fluid dynamics) An exact solution of the Euler equations for periodic surface gravity waves, describing a progressive wave of permanent form on the surface of an incompressible fluid of infinite depth.


Mach wave

(fluid dynamics) A pressure wave travelling at the speed of sound, caused by a slight change of pressure added to a compressible flow.


time-average equation

(fluid dynamics) The equation, 1/(V_M)=ϕ/(V_F)+(1-ϕ)/(V_R), used in acoustic log interpretation as a measurement of formation porosity.


tea leaf paradox

(fluid dynamics) The phenomenon whereby tea leaves in a cup of tea migrate to the center and bottom of the cup after being stirred (due to friction towards the bottom), rather than being forced to the edges, as would be expected in a spiral centrifuge.


teapot effect

(fluid dynamics) The phenomenon whereby a liquid being poured from a container runs down the spout or the body of the container instead of flowing out in an arc.


superposition in time

(fluid dynamics) A computation accounting for the flowrate history in an analytical model that is generated to match with pressure-transient test data.


adjusted flow time

adjusted flow time (countable and uncountable, plural adjusted flow times)

(fluid dynamics) Of a well-test, a calculation of the cumulative well production since the last extended shut-in period, divided by the flowrate immediately before the moment a well is shut in for a buildup test.


thickening time

thickening time (countable and uncountable, plural thickening times)

(fluid dynamics) The total amount of time in which a cement slurry will remain in a fluid state under simulated downhole conditions and is capable of being pumped.


Kaye effect

Named after British engineer Alan Kaye who first described the effect in 1963.

(fluid dynamics) A phenomenon where pouring a viscous mixture of an organic liquid onto a surface causes a jet of liquid to spout upward from the surface while merging with the descending one.


Weissenberg effect

Weissenberg effect (plural Weissenberg effects)

(fluid dynamics) A phenomenon that occurs when a spinning rod is inserted into a solution of elastic liquid. Instead of being thrown outward, the solution is drawn towards the rod and rises up around it.


Archimedes number

Archimedes number (plural Archimedes numbers)

Named after Archimedes of Syracuse (c. 287 – c. 212 BC), a Greek mathematician, physicist, engineer, inventor, and astronomer.

(fluid dynamics) A dimensionless number used to determine the motion of fluids due to density differences, defined as the ratio of gravitational forces to viscous forces: Ar=(gL³(ρ-ρ_ℓ)/(ρ_ℓ))/(ν²)=(gL³ρ_ℓ(ρ-ρ_ℓ))/(μ²)\, where g is the local external field, L is the characteristic length of body, (ρ-ρ_ℓ)/(ρ_ℓ) is the submerged specific gravity, ρ_ℓ is the density of the fluid, ρ is the density of the body, ν=μ/(ρ_ℓ) is the kinematic viscosity, and μ is the dynamic viscosity.


Bejan number

(fluid dynamics) A dimensionless number: the pressure drop along the fluid path length in both external flows and internal flows: Be_L=(Δp,L²)/(μν), where μ is the dynamic viscosity, ν is the momentum diffusivity (or Kinematic viscosity) and L is fluid path length.


Atwood number

(fluid dynamics) A dimensionless number used in the study of hydrodynamic instabilities in density stratified flows: A=(ρ₁-ρ₂)/(ρ₁+ρ₂), where ρ₁ is the density of the heavier fluid and ρ₂ is the density of the lighter fluid.


vortex line

(fluid dynamics) A line whose tangent is everywhere parallel to the local vorticity vector.