Fr.: flot d'accrétion
1) Flow of matter during an accretion process.
Fr.: flot bipolaire
Same as → bipolar outflow.
Fr.: flot bipolaire
A flow of gaseous material in two opposite directions emanating from protostellar regions or from → evolved stars during the early post-→ AGB evolution. In protostellar regions → molecular outflows are pushed by → bipolar jets.
Fr.: flot champagne
Fr.: flot circumstellaire
A stream of matter into the interstellar medium from a central star.
cold accretion flow
tacân-e farbâl-e sard
Fr.: écoulement d'accrétion froid
1) A type of → accretion flow by a
→ compact object
such as a → black hole
that consists of cool → optically thick
gas and has a relatively high mass → accretion rate,
in contrast to → hot accretion flows.
tacân-e tanjidani, ~ tanješpazir
Fr.: flot compressible
A flow in which changes of the density, induced by velocities and their fluctuations, are not negligible.
Fr.: flot de refroidissement
A phenomenon observed in a → cluster of galaxies, whereby the cluster core loses energy via X-ray radiation because of the collisions between the gas particles. The radiation rate is proportional to the square of the density, and the → cooling time, which remains in the outer parts too large, becomes smaller than the → Hubble time in the core. As a result, the central regions of clusters of galaxies cool down; and since in the center of a cluster gas pressure and gravitational attraction are in equilibrium, the gas density has to rise to maintain the pressure necessary for supporting the outer layers of gas. To cause its density to rise, the cooled gas has to flow inward. As the densest gas, which cools quickest, is already concentrated in the center of the cluster, the inward flow will start at the center, soon followed by the outer layers. This flow of gas is called the cooling flow. Cooling flows are moderated through feedback due to the → supermassive black hole in the nucleus of the central galaxy. The gas inflow to the center fuels the → active galactic nucleus (AGN). The latter then heats again the gas through its → radio jets.
Fr.: écoulement de Couette
In fluid dynamics, the motion of an → incompressible → laminar flow passing between two parallel plates, when the upper plate is moving with some velocity while the lower one is stationary. The flow is driven owing to the fluid → viscosity and the applied pressure gradient parallel to the plates. See also → Taylor-Couette flow.
Named after Maurice Marie Alfred Couette (1858-1943), a French physicist who dealt mainly with fluid mechanics; → flow
Fr.: écoulement de Couette-Taylor
In fluid mechanics, the motion of a fluid between two concentric cylinders when one or both of the cylinders rotate.
The movement of a fluid in the opposite direction to a fluid flowing in the same cross section of a turbulent medium.
1) tacân; 2) tacidan
Fr.: 1) flot, écoulement; 2) couler, s'écouler
O.E. flowan, from P.Gmc. *flo- (cf. Du. vloeien "to flow," O.H.G. flouwen "to rinse, wash"), probably from PIE *pleu- "to flow, float" (cf. Skt. plavate "navigates, swims," plavayati "overflows;" Gk. plyno "I wash," pleo "swim, go by sea;" L. pluere "to rain;" Arm. helum "I pour;" Lith. pilu "to pour out").
1) Tacân, from tac- variant tâz- present stem of
tacidan, tâxtan, tâzidan "to run; to hasten; to assault,"
+ noun and adj. suffix -ân. Related to the first component are
Mod.Pers. tajan name of a river (initially "flowing, streaming, stream"),
tâzi "swift (greyhound)," tak "running, rush," from
Mid.Pers. tâz-, tâxtan "to flow, to cause to walk," tc- "to flow, to walk,"
tag "running, attack," tâzig "swift, fast;"
Khotanese ttajs- "to flow, to walk;" Av. tac- "to run, to flow,"
taciāp- "flowing water," tacinti (3pl.pers.act.) "to flow,"
tacar- "course," tacan "current, streaming;" cf.
Skt. tak- "to rush, to hurry," takti "runs;"
O.Ir. tech- "to flow;" Lith. teketi
"to walk, to flow;" O.C.S. tešti "to walk, to hurry;" Tokharian B cake
"river;" PIE base *tekw- "to run; to flow."
Fr.: ligne d'écoulement
Same as → streamline.
Fr.: tube d'écoulement
Same as → stream tube.
Fr.: aptitude à s'écouler, coulabilité
The ability of a body of matter (liquid, gas, loose particulate solid) to flow.
Tacandegi, from tacandé (originally tacandag), agent noun of tacidan, → flow, + noun suffix -i.
Fr.: écoulement forcé
A fluid flow generated when external forces cause the fluid to flow, for example when a flow is caused by a pump. It contrasts with → free flow.
Fr.: écoulement libre
A fluid flow which develops when density differences within the fluid are the only driving forces. See also → forced flow.
Fr.: flot galactique
ostacân bâ marpel-e kahkešâni
Fr.: flot à l'échelle galactique
The enormous amounts of → mass and → energy released from active galaxies into the → intergalactic medium. → Supermassive black holes, believed to exist at the centres of active galaxies (→ active galaxy), → accrete matter and liberate huge quantities of energy. The energy output is often observed as → active galactic nuclei (AGN) outflows in a wide variety of forms, e.g. → collimated → relativistic jets and/or huge overpressured cocoons in → radio, → blueshifted broad → absorption lines in the → ultraviolet and → optical, → warm absorbers and ultrafast outflows in → X-rays, and → molecular gas in → far infrared. Moreover, the processes of → star formation and → supernova explosions release mass/energy into the surroundings. This → stellar feedback heats up, ionizes and drives gas outward, often generating large-scale outflows/→ winds. Galactic outflows are observed at low redshifts reaching a velocity as large as 1000 km s-1 and at high-z up to z ~ 5, sometimes extending over distances of 60-130 kpc. Galactic-scale outflows may be a primary driver of galaxy evolution through the removal of cool gas from star-forming regions to a galaxy's → halo or beyond.