A continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; collective term for liquids and gases.
From L. fluidus "fluid, flowing," from fluere "to flow;" → flux.
Šârré, from šârr, → flux.
Fr.: dynamique des fluides
The branch of → fluid mechanics that deals with the movement of gases and liquids.
Fr.: mécanique des fluides
The ability of a substance to flow; reciprocal of → viscosity.
šârre-ye hamgen (#)
Fr.: fluide homogène
A fluid with uniform properties throughout, but meteorologists sometimes designate as homogeneous a fluid with constant density.
šâre-ye ârmâni, ~ minevâr
Fr.: fluide idéal
Fr.: fluide newtonien
Fr.: magnétohydrodynamique à une fluide
A → magnetohydrodynamics treatment in which the → plasma consists only of one particle species and moves with the bulk speed. The thermal motion of the particles is neglected and thus there is no motion of particles relative to each other.
Fr.: fluide réel
The opposite of an ideal fluid; a fluid which possesses viscosity and therefore exhibits certain frictional phenomena. Viscosity arises due to cohesive forces between molecules and molecular momentum exchange between fluid layers. These effects appear as tangential or shear stresses between moving fluid layers.
Fr.: fluide supercritique
A fluid that is at a temperature and pressure above its thermodynamic critical point. In these conditions the substance acquires unique characteristics of density and mobility. Supercritical fluids exist deep inside some planets; for example, there is supercritical water deep inside the Earth.
A → fluid that exhibits frictionless flow, very high heat → conductivity, and other unusual physical properties. For example, → liquid helium at the temperature about 2.17 K (→ lambda point) becomes a zero → viscosity fluid which will move rapidly through any pore in the apparatus. See also → helium II.
šârre-ye vošksân (#)
Fr.: fluide visqueux
A fluid whose viscosity is sufficiently large to make the viscous forces a significant part of the total force field in the fluid.