The Eckert number (Ec) is a
dimensionless number
Dimensionless quantities, or quantities of dimension one, are quantities implicitly defined in a manner that prevents their aggregation into unit of measurement, units of measurement. ISBN 978-92-822-2272-0. Typically expressed as ratios that a ...
used in
continuum mechanics
Continuum mechanics is a branch of mechanics that deals with the deformation of and transmission of forces through materials modeled as a ''continuous medium'' (also called a ''continuum'') rather than as discrete particles.
Continuum mec ...
. It expresses the relationship between a flow's
kinetic energy
In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion.
In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
and the boundary layer
enthalpy
Enthalpy () is the sum of a thermodynamic system's internal energy and the product of its pressure and volume. It is a state function in thermodynamics used in many measurements in chemical, biological, and physical systems at a constant extern ...
difference, and is used to characterize heat transfer
dissipation
In thermodynamics, dissipation is the result of an irreversible process that affects a thermodynamic system. In a dissipative process, energy ( internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, wh ...
.
It is named after
Ernst R. G. Eckert
Ernst Rudolph Georg Eckert (September 13, 1904 – July 8, 2004) was an Austrian American engineer and scientist who advanced the film cooling technique for aeronautical engines. He earned his Diplom Ingenieur and doctorate in 1927 and 1931, respe ...
.
It is defined as
:
where
* ''u'' is the local
flow velocity
In continuum mechanics the flow velocity in fluid dynamics, also macroscopic velocity in statistical mechanics, or drift velocity in electromagnetism, is a vector field used to mathematically describe the motion of a continuum. The length of the f ...
of the continuum,
* ''c
p'' is the constant-pressure local
specific heat
In thermodynamics, the specific heat capacity (symbol ) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat ...
of the continuum,
*
is the difference between wall temperature and local temperature.
References
Dimensionless numbers of fluid mechanics
Dimensionless numbers of thermodynamics
Continuum mechanics
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