fluid

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adjective

1. Changing easily, as in expression: changeable, mobile, plastic. See change/persist.
2. Marked by facility, especially of expression: easy, effortless, flowing, fluent, graceful, smooth. See style/good style/bad style.
3. Capable of or liable to change: alterable, changeable, inconstant, mutable, uncertain, unsettled, unstable, unsteady, variable, variant. Archaic various. See change/persist.

Definition: adaptable, changeable
Antonyms: inflexible, stable, unchangeable

adj

Definition: liquid
Antonyms: solid

n

Definition: liquid
Antonyms: solid

A substance that flows when subjected to shear stress. Gases and liquids are fluids with similar mechanical properties.

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In physics, a substance that flows — usually a liquid or a gas.

1. a liquid or gas; any liquid of the body.
2. composed of molecules which freely change their relative positions without separation of the mass.

• allantoic f. — the fluid contained within the allantois.
• amniotic f. — the fluid within the amnion that bathes the developing fetus and protects it from mechanical injury.
• ascitic f. — see ascites.
• f. balance — a state in which the volume of body water and its solutes (electrolytes and nonelectrolytes) are within normal limits and there is normal distribution of fluids within the intracellular and extracellular compartments. The total volume of body fluids should be about 60% of the body weight, and it should be distributed so that one-third is extracellular fluid and two-thirds intracellular fluid. Although this distribution remains constant in a healthy animal, there is continuous movement of fluid into and out of the various compartments. See also dehydration, water intoxication.
• body f's — the fluids within the body, composed of water, electrolytes and nonelectrolytes. The volume and distribution of body fluids vary with age, sex and amount of adipose tissue. Throughout life there is a slow decline in the volume of body fluids; obesity decreases the relative amount of water in the body.
— Although the body fluids are continuously in motion, moving in and out of the cells, tissue spaces and vascular system, physiologists consider them to be ‘compartmentalized’. Fluid within the cell membranes is called intracellular fluid and comprises about two-thirds of the total body fluids. The remaining one-third is outside the cell and is called extracellular fluid. The extracellular fluid can be further divided into tissue fluid (interstitial fluid), which is found in the spaces between the blood vessels and surrounding cells, and intravascular fluid, which is the fluid component of blood. — The maintenance of a proper balance between the intracellular and extracellular fluid volumes is essential to health. In patients with heart failure and renal failure the balance becomes upset, producing either localized or generalized edema. Excessive fluid loss produces fluid volume deficit causing cellular dehydration and impaired cellular function.
• Bouin's f. — a histological fixative.
• cerebrospinal f. — the fluid contained within the ventricles of the brain, the subarachnoid space, and the central canal of the spinal cord. See also cerebrospinal fluid.
• f. dram — see fluid dram.
• f. extract — a liquid preparation of a vegetable drug, containing alcohol as a solvent or preservative, or both, of such strength that each milliliter contains the therapeutic constituents of 1 gram of the standard drug it represents.
• fetal f. — allantoic plus amniotic fluids.
• interstitial f. — the extracellular fluid bathing the cells in most tissues, excluding the fluid within the lymph and blood vessels.
• isotonic f. — having the same tonicity or osmotic pressure as blood.
• lacrimal f. — aqueous fluid secreted by the lacrimal glands; called also tears.
• f. line — in radiographs, the interface between fluid and gas, as in the gastrointestinal tract, will show as a straight line.
• f. loss — by vomiting, diarrhea, polyuria, water deprivation. See dehydration.
• f. mosaic model — the modern concept of the structure of a biological membrane developed by S.J. Singer and G.L. Nicolson. In it the membrane consists of protein molecules partly embedded in a discontinuous bilayer of phospholipids that form the matrix of a mosaic of functional cell units.
• f. ounce — see fluid ounce.
• pericardial, pleural, peritoneal f. — normally present in amounts sufficient only to lubricate the movement of viscera within the respective cavities. Composition similar to blood serum.
• f. replacement — see fluid therapy (below).
• f. restriction — the limitation of oral fluid intake to a prescribed amount for each 24-hour period.
• f. retention — see edema.
• spinal f. — the fluid within the spinal canal.
• f. splashing sounds — audible when gas and fluid are free in a cavity, e.g. abomasum in cases of abomasal displacement; can be elicited by shaking a small animal or part of a large animal (i.e. succussion) or by simultaneous percussion and auscultation.
• synovial f. — synovia.
• f. therapy — aims to replace fluids lost by disease process or by restriction of intake, or to maintain a high rate of fluid excretion to ensure removal of toxins, or to administer therapeutic or anesthetic agents slowly over a long period. The amounts and route of administration vary with the need of the patient. Normal solutions include 5% dextrose and Ringer's solution; alkalinizing fluids include lactated Ringer's and 1.3% sodium bicarbonate; acidifying solutions include isotonic saline and 1.9% ammonium chloride.
• f. thrill — see thrill.
• f. volume deficit — an imbalance in fluid volume in which there is loss of fluid from the body not compensated for by an adequate intake of water. The major causes are: (1) insufficient fluid intake, and (2) excessive fluid loss from vomiting, diarrhea, suctioning of gastric contents, or drainage through operative wounds, burns or fistulae. Decreased volume in the intravascular compartment is called hypovolemia. Because water moves freely between the compartments, extracellular fluid deficit causes intracellular fluid deficit (cellular dehydration), which leaves the cells without adequate water to carry on normal function.
• f. volume excess — an overabundance of water in the interstitial fluid spaces or body cavities (edema) or an excess of fluid within the blood vessels (hypervolemia) and water intoxication.
— Factors that contribute to the accumulation of edematous fluid are: (1) dilatation of the arteries, as occurs in the inflammatory process; (2) reduced effective osmotic pressure, as in hypoproteinemia, lymphatic obstruction and increased capillary permeability; (3) increased venous pressure, as in congestive heart failure, thrombophlebitis and cirrhosis of the liver; and (4) retention of sodium due to increased reabsorption of sodium by the renal tubules.
• f. wave — see thrill.

A liquid or gaseous substance.

• Principles of Mechanics, Waves, and Measurement - fluid: material that flows, such as liquid or gas
• Substances, Particles, and Atomic Architecture - fluid: material that flows; liquid or gas
• Active, Lively, Awake, or Limber

This article is about the concept in physics. For other uses, see Fluid (disambiguation).

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2009)

Continuum mechanics
Laws Conservation of mass Conservation of momentum Conservation of energy Entropy inequality
Solid mechanics Solids Stress · Deformation Compatibility Finite strain · Infinitesimal strain Elasticity (linear) · Plasticity Bending · Hooke's law Failure theory Fracture mechanics Frictionless/Frictional Contact mechanics
Fluid mechanics Fluids Fluid statics · Fluid dynamics Surface tension Navier–Stokes equations Viscosity: Newtonian, Non-Newtonian
Rheology Viscoelasticity Smart fluids: Magnetorheological Electrorheological Ferrofluids Rheometry · Rheometer
Scientists Bernoulli · Cauchy · Hooke Navier · Newton · Stokes
v t e

In physics, a fluid is a substance that continually deforms (flows) under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids.

In common usage, "fluid" is often used as a synonym for "liquid", with no implication that gas could also be present. For example, "brake fluid" is hydraulic oil and will not perform its required function if there is gas in it. This colloquial usage of the term is also common in medicine and in nutrition ("take plenty of fluids").

Liquids form a free surface (that is, a surface not created by the container) while gases do not. The distinction between solids and fluid is not entirely obvious. The distinction is made by evaluating the viscosity of the substance. Silly Putty can be considered to behave like a solid or a fluid, depending on the time period over which it is observed. It is best described as a viscoelastic fluid. There are many examples of substances proving difficult to classify. A particularly interesting one is pitch, as demonstrated in the pitch drop experiment currently running at the University of Queensland.

Contents 1 Physics 1.1 Modelling 2 See also 3 References

Physics

Fluids display properties such as:

• not resisting deformation, or resisting it only lightly (viscosity), and
• the ability to flow (also described as the ability to take on the shape of the container).This also means that all fluids have the property of fluidity.

These properties are typically a function of their inability to support a shear stress in static equilibrium.

Solids can be subjected to shear stresses, and to normal stresses—both compressive and tensile. In contrast, ideal fluids can only be subjected to normal, compressive stress which is called pressure. Real fluids display viscosity and so are capable of being subjected to low levels of shear stress.

Modelling

Main article: Fluid mechanics

In a solid, shear stress is a function of strain, but in a fluid, shear stress is a function of strain rate. A consequence of this behavior is Pascal's law which describes the role of pressure in characterizing a fluid's state.

Depending on the relationship between shear stress, and the rate of strain and its derivatives, fluids can be characterized as one of the following:

• Newtonian fluids : where stress is directly proportional to rate of strain

• Non-Newtonian fluids : where stress is not proportional to rate of strain, its higher powers and derivatives.

The behavior of fluids can be described by the Navier–Stokes equations—a set of partial differential equations which are based on:

• continuity (conservation of mass),
• conservation of linear momentum,
• conservation of angular momentum,
• conservation of energy.

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

See also

• Matter
• Liquid
• Gas

References

• Bird, Byron; Stewart, Warren & Lightfoot, Edward (2007). Transport Phenomena. New York: Wiley, Second Edition. pp. 912. ISBN 0-471-41077-2. 

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - væske, flydende legeme
adj. - flydende, væskeformig, væske-, ubestemt

idioms:

• fluid ounce    rummål, 28,41 milliliter

Nederlands (Dutch)
vloeistof, vloeibaar, soepel, beweeglijk, meteen in baar geld om te zetten, klinkende munt

Français (French)
n. - (Biol) liquide, (Chim, Tech) fluide
adj. - (gén) liquide, (Chim, Tech) fluide, vague, fluide (un style)

idioms:

• fluid ounce    (Mes) once liquide (= 0,03 litres)

Deutsch (German)
n. - Flüssigkeit
adj. - flüssig

idioms:

• fluid ounce    Unze (0,002841 l)

Ελληνική (Greek)
n. - ρευστό, υγρό
adj. - υγρός, ρευστός, ρέων, ευμετάβλητος, ασταθής

idioms:

• fluid ounce    28 κυβικά εκατοστόμετρα

Italiano (Italian)
liquido, fluido

idioms:

• fluid ounce    oncia liquida

Português (Portuguese)
n. - fluido (m)
adj. - fluido (m), líquido (m)

idioms:

• fluid ounce    onça (f) fluída (unidade de medida)

Русский (Russian)
жидкость, текучая среда, неустойчивый, подвижной

idioms:

• fluid ounce    жидкая унция

Español (Spanish)
n. - líquido, fluido
adj. - líquido, fluido, inestable, cambiadizo

idioms:

• fluid ounce    onza líquida

Svenska (Swedish)
n. - icke fast kropp (fys.), fluidum
adj. - flytande, obestämd, likvid

中文（简体）(Chinese (Simplified))
液体, 流体, 分泌液, 流动的, 不安定的, 可改变的

idioms:

• fluid ounce    液量盎司

中文（繁體）(Chinese (Traditional))
n. - 液體, 流體, 分泌液
adj. - 流動的, 不安定的, 可改變的

idioms:

• fluid ounce    液量盎司

한국어 (Korean)
n. - 유체, 유동체
adj. - 유동성의

日本語 (Japanese)
adj. - 流動する, 流動性の, 流動的な
n. - 流動体, 流体

idioms:

• fluid ounce    液量オンス

العربيه (Arabic)
‏(الاسم) مادة سائله أو مائعه (صفه) سائل , مائع‏

עברית (Hebrew)
n. - ‮גז, נוזל, הפרשה נוזלית‬
adj. - ‮משתנה, גמיש, נוזלי, לא-מוצק‬

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