An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Oceanography: A flow resulting from → geostrophic balance. In geostrophic flow water moves along the lines of constant pressure or → isobars. Geostrophic flow is characterized by small → Rossby and → Ekman numbers.

→ geostrophic; → flow.

A type of → accretion flow by a → compact object such as a → black hole which has a high → virial temperature, is → optically thick, and occurs at lower mass → accretion rates compared with → cold accretion flows. In a hot accretion flow with a very low mass accretion rate, the electron mean free path is very large, and so the accreting → plasma is nearly collisionless. In this type of accretion flow, thermal conduction transports the energy from the inner to the outer regions. As the gas temperature in the outer regions can be increased above the → virial temperature , the gas in the outer regions can escape from the gravitational potential of the central black hole and form outflows, significantly decreasing the mass accretion rate.

→ cold; → accretion; → flow.

→ Hubble-Lemaitre flow.

→ Hubble; → flow.

The general outward motion of → galaxy clusters resulting from the → expansion of the Universe.

→ Hubble-Lemaitre law; → flow.

A flow whose volume or density does not change under pressure, and therefore its density is a constant. In other words, an ideal flow in which the → divergence of velocity is zero. → compressible flow.

→ incompressible, from → in "not" + → compressible; → flow.

1) The act or process of flowing in or into. Something that flows in or into. Opposite of → outflow.
2) Meteo: Flow of water into a stream, lake, reservoir, container, basin, aquifer system, etc.

Inflow, from → in- + → flow.

The flow of data into a system or to the end users.

→ information; → flow.

A → reversible flow in which the value of → entropy remains → constant; i.e. no energy is added to the flow, and no energy losses occur due to friction or dissipative effects.

→ isentropic; → flow.

A flow in which the particles of fluid are moving orderly, and in which adjacent layers or laminas glide smoothly over another with little mixing between them. A laminar flow may rapidly transform into a → turbulent flow for large → Reynolds numbers.

→ laminar; → flow.

A turbulent flow in which viscous forces are negligible compared to nonlinear advection terms, which characterize the variation of fluid quantities. The dynamics becomes generally turbulent when the Reynolds number is high enough. However, the critical Reynolds number for that is not universal, and depends in particular on boundary conditions.

→ large; → Reynolds number; → flow.

Same as → streamline.

→ line; → flow.

The mass of a fluid that passes a specified unit area in a unit amount of time.

→ mass; → flow.

The flowing out of mass through various processes from an object, for example in a star forming region or in a close binary.

→ mass; → outflow.

Meteo.: A flow between the poles, or between the equator and the poles. A positive value indicates flow away from the equator; a negative value, flow toward the equator.

→ meridional; → flow.

An outflow of molecular material, often → bipolar, observed in the regions of → star formation. Molecular outflows are thought to be driven by → bipolar jets from → protostars. They are probably → bow shocks which have had time to cool and be observable in molecular lines. Molecular outflows are poorly → collimated compared to the jets and tend to be slow moving (velocities 10-20 km s^-1). Some bipolar outflows may be driven by → stellar winds.

→ molecular; → outflow.

A hypothetical flow in which all the flow parameters may be expressed as functions of time and one space coordinate only. This single space coordinate is usually the distance measured along the center-line of some conduit in which the fluid is flowing (B. Massey, Mechanics of Fluids, Taylor & Francis, 2006).

→ one; → dimensional; → flow.

The act of flowing out; a fluid that flows out; any outward movement. Opposite of → inflow.

→ out + → flow.

In computers, the condition arising when the result of an arithmetic operation exceeds the capacity of the number representation.

→ over-; → flow.

Sarriz, from sar, → head, + riz present stem of rixtan "to flow, to pour" (Mid.Pers. rēxtan and rēcitan "to flow;" Av. raēk- "to leave, set free; to yield, transfer," infinitive *ricyā; Mod.Pers; rig in morderig "heritage" (literally, "left by the dead"); cf. Skt. rinakti "he leaves," riti- "stream; motion, course;" L. rivus "stream, brook;" Old Church Slavic rēka "river;" Rus. reka "river;" Goth. rinnan "run, flow," rinno "brook;" O.E. ridh "stream").

A process in a → binary system when a star fills its → Roche lobe, often by becoming a → giant or → supergiant during the later stages of → stellar evolution. When the star expands, any material that passes beyond the Roche lobe will flow onto the binary → companion, often by way of an → accretion disk. This occurs through the → inner Lagrangian point where the gravity of the two stars cancels. The RLOF is responsible for a number of phenomena including → cataclysmic variables, → Type Ia supernovae, and many → X-ray binary systems.

→ Roche lobe; → overflow.

A flow in which the characterizing conditions, such as → streamlines or velocity at any given point, do not change with time.

→ steady; → flow.

Tacân, → flow; pâyâ "steady, constant," from pâyidan "to stand firm, to be constant, steady," from Mid.Pers. pattây-, pattutan "to last, endure, stay."