second law of thermodynamics
qânun-e dovom-e garmâtavânik
Fr.: deuxième loi de la thermodynamique
1) Heat cannot be transferred from a colder to a hotter body without some other effect, i.e.
without → work being done. Expressed in terms of
→ entropy: the entropy of an
→ isolated system tends toward a maximum and its
available energy tends toward a minimum.
Smoothed Particle Hydrodynamics (SPH)
hidrotavânik-e zarrehâ-ye hamvâridé
Fr.: hydrodynamique des particules lissées
A numerical method for modeling → compressible hydrodynamic flows, which uses particles to simulate a continuous fluid flow. Because the system of hydrodynamical basic equations can be analytically solved only for few exceptional cases, the SPH method provides a numerical algorithm to solve systems of coupled → partial differential equations for continuous field quantities. The main advantage of the method is that it does not require a computational grid to calculate spatial → derivatives and that it is a Lagrangian method, which automatically focuses attention on fluid elements. The equations of motion and continuity are expressed in terms of ordinary differential equations where the body forces become classical forces between particles. This method was first independently developed by Lucy (1977, AJ 82, 1013) and Gingold & Monaghan (1977, MNRAS 181, 375).
Fr.: thermodynamique statistique
Same as → statistical mechanics.
Fr.: dynamique stellaire
The field of astrophysics that describes systems of many → point mass particles whose mutual gravitational interactions determine their orbits. Theses systems include → star clusters, → globular clusters, and galaxies (→ galaxy) consisting of about 102-103, 104-106, and up to about 1012 members respectively. Stellar dynamics deals with systems in which each member contributes importantly to the overall gravitational field and is usually concerned with the statistical properties of many orbits. It can be compared to the → kinetic theory of gases developed in the late 19th century. In contrast, → celestial mechanics deals with systems where the gravitational force of a massive planet or star determines the orbits of its satellites.
A branch of physics concerned with the relations between heat and other forms of energy and how these affect temperature, pressure, volume, mechanical action, and work.
third law of thermodynamics
qânun-e sevom-e garmâtavânik
Fr.: troisième loi de la thermodynamique
The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.
zeroth law of thermodynamics
qânun-e sefrom-e garmâtavânik
Fr.: loi zéro de la thermodynamique
Two objects that are in → thermal equilibrium with a third object will be in thermal equilibrium with each other.