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Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them. [ 1 ] : 3 It has applications in a wide range of disciplines, including mechanical , aerospace , civil , chemical , and biomedical engineering , as well as geophysics , oceanography , meteorology , astrophysics ...
This article summarizes equations in the theory of fluid mechanics. Definitions. Flux F through a surface, dS is the differential vector area element, ...
the fluid is assumed to be isotropic, as with gases and simple liquids, and consequently is an isotropic tensor; furthermore, since the deviatoric stress tensor is symmetric, by Helmholtz decomposition it can be expressed in terms of two scalar Lamé parameters, the second viscosity and the dynamic viscosity, as it is usual in linear elasticity:
The vorticity equation of fluid dynamics describes the evolution of the vorticity ω of a particle of a fluid as it moves with its flow; that is, the local rotation of the fluid (in terms of vector calculus this is the curl of the flow velocity). The governing equation is:
Fluid statics or hydrostatics is the branch of fluid mechanics that studies fluids at hydrostatic equilibrium [1] and "the pressure in a fluid or exerted by a fluid on an immersed body". [ 2 ] It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics , the study of fluids in motion.
This is why static pressure and dynamic pressure are never the same in a system in which the fluid is in motion. This pressure difference arises from a change in fluid velocity that produces velocity head, which is a term of the Bernoulli equation that is zero when there is no bulk motion of the fluid. In the picture on the right, the pressure ...
The free Euler equations are conservative, in the sense they are equivalent to a conservation equation: + =, or simply in Einstein notation: + =, where the conservation quantity in this case is a vector, and is a flux matrix. This can be simply proved.
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, [1] i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.