# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 10 Search : hydrodynamic
 hydrodynamic   هیدروتوانیک   hirdrotavânikFr.: hydrodynamique   Of or pertaining to → hydrodynamics.→ hydro- + → dynamic. hydrodynamic equation   هموگش ِ هیدروتوانیک   hamugeš-e hirdrotavânikFr.: équation hydrodynamique   Fluid mechanics: A → partial differential equation which describes the motion of an element of fluid subjected to different forces such as pressure, gravity, and frictions.→ hydrodynamic; → equation. hydrodynamic equilibrium   ترازمندی ِ هیدروتوانیک   tarâzmandi-ye hirdrotavânikFr.: équilibre hydrodynamique   The state of a star when all its internal forces are in equilibrium. The main forces are gas pressure, radiation pressure due to thermonuclear fusion that tends to disrupt the star, and the opposing gravity. → hydrostatic equilibrium.→ hydrodynamic; → equilibrium. hydrodynamics   هیدروتوانیک   hidrotavânikFr.: hydrodynamique   The branch of physics dealing with the motion, energy, and pressure of neutral → fluids.→ hydro- + → dynamics. ideal magnetohydrodynamics (MHD)   مغنات-و-هیدروتوانیک ِ آرمانی، ~ مینه‌وار   meqnâtohidrotavânik-e ârmâni, ~ minevârFr.: magnétohydrodynamique idéale   Magnetohydrodynamics of a → plasma with very large (infinite) → conductivity. In this condition, → Ohm's law reduces to E = -v × B, where E represents → electric field, B → magnetic field, and v the → fluid velocity. Ideal MHD is the simplest model to describe the dynamics of plasmas immersed in a magnetic field. It is concerned with → one-fluid magnetohydrodynamics and neglects → resistivity. This theory treats the plasma composed of many charged particles with locally neutral charge as a continuous single → fluid. Ideal MHD does not provide information on the velocity distribution and neglects the physics relating to wave-particle interactions, as does the two-fluid theory as well. It does have the advantage that the macroscopic dynamics of the → magnetized plasma can be analyzed in realistic three-dimensional geometries (K. Nishikawa & M. Wakatani, 2000, Plasma Physics, Springer). See also → non-ideal magnetohydrodynamics.→ ideal; → magnetohydrodynamics. magnetohydrodynamic   مغنات-و-هیدروتوانیک   meqnâtohidrotavânikFr.: magnétohydrodynamique   Of or relating to → magnetohydrodynamics.→ magneto- + → hydrodynamic. magnetohydrodynamics (MHD)   مغنات-و-هیدروتوانیک   meqnâtohidrotavânikFr.: magnétohydrodynamique   The dynamics of an ionized plasma in the non-relativistic, collisional case. In this description, charge oscillations and high frequency electromagnetic waves are neglected. It is an important field of astrophysics since plasma is one of the commonest forms of matter in the Universe, occurring in stars, planetary magnetospheres, and interplanetary and interstellar space.From → magneto- + → hydrodynamics. non-ideal magnetohydrodynamics (MHD)   مغنات-و-هیدروتوانیک ِ نا-آرمانی، ~ نا-مینه‌وار   meqnâtohidrotavânik-e nâ-ârmâni, ~ nâ-minevârFr.: magnétohydrodynamique non idéale   A → magnetohydrodynamics approach dealing with → plasmas which is an improvement with respect to → ideal magnetohydrodynamics. Non-ideal magnetohydrodynamics allows for a drift between particles, redistributing the → magnetic flux and acting on both the → angular momentum and magnetic flux conservation issues.→ non-→ ideal; → magnetohydrodynamics. one-fluid magnetohydrodynamics   مغنات-و-هیدروتوانیک ِ تک-شاره   meqnâtohidrotavânik-e tak-šâreFr.: 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.→ one; → fluid; → magnetohydrodynamics. Smoothed Particle Hydrodynamics (SPH)   هیدروتوانیک ِ ذره‌های ِ همواریده   hidrotavânik-e zarrehâ-ye hamvâridéFr.: 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).Smoothed Particle Hydrodynamics, first used by Gingold & Monaghan (1977); → smooth; → particle; → hydrodynamics.