A → thermodynamic process that occurs without
→ loss or → gain of
From Gk. adiabatos "impassable," from a- "not" + diabatos "passable," from diabainein "to go across," from dia- " through" + bainein "to go."
Bidarrow from bi- "not; without" + darrow "way out," from dar "out" + row "to go, going," from raftan "to go."
degaršod-e bidarrow, degareš-e ~
Fr.: changement adiabatique
A change taking place in a system that has perfect thermal insulation, so that heat cannot enter or leave the system and energy can only be transferred by work.
Fr.: indice adiabatique
Of a gas, the ratio of its → specific heat at constant pressure to its specific heat at constant volume: γ = CP/ CV.
adiabatic initial conditions
butârhâ-ye âqâzin-e bidarrow
Fr.: conditions initiales adiabatiques
The assumption whereby the density fluctuations in the very → early Universe would be produced by compressing or decompressing of all components of a homogeneous Universe. The adiabatic initial conditions lead to coherent oscillations in the form of peaks in the → temperature anisotropy spectrum. See also → acoustic peak, → baryon acoustic oscillation.
Fr.: phase adiabatique
Same as the → Sedov-Taylor phase.
Fr.: processus adiabatique
→ adiabatic, → process.
Fr.: choc adiabatique
adiabatic temperature gradient
zine-ye damâ-ye bidarrow
Fr.: gradient de température adiabatique
The temperature gradient defining the → radiative equilibrium condition in a region. It is expressed as: dT/dr = (1 - 1/ γ)((T / P)(dP / dr), where T and P are temperature and pressure, dT / dr and dP / dr temperature and pressure gradients respectively, and γ = CP / CV. For radiative equilibrium to be stable against → convection, the actual temperature gradient must be less than the adiabatic temperature gradient, i.e. |dT /dr|rad < |dT /dr|ad. See also → Schwarzschild's criterion.
superadiabatic temperature gradient
zine-ye damâ-ye abar-bidarrow
Fr.: gradient de température super-adiabatique
A condition in which there is an excess of the actual temperature gradient over the → adiabatic temperature gradient corresponding to the same pressure gradient. A region with superadiabatic temperature gradient is convectively unstable. → Hayashi forbidden zone.