Navier-Stokes equation هموگش ِ ناویه-استوکس hamugeš-e Navier-Stokes
*Fr.: équation de Navier-Stokes*
One of a set of → *differential equation*s that
describes the motion of a → *fluid* as a function of
→ *pressure*, → *density*,
total external force, and
→ *viscosity*. See also
→ *Euler equation*. Named after Claude-Louis Navier (1785-1836), a French engineer and physicist,
and George Gabriel Stokes, → *stokes*;
→ *equation*. |

stokes (st) استوکس stokes (#)
*Fr.: stokes*
The unit of → *viscosity* in the → *cgs*
system, cm^{2} s^{-1}, equal to 10^{-4} m^{2} s^{-1}. After Sir George Gabriel Stokes (1819-1903), a
British mathematician and physicist, who
made important contributions to fluid dynamics, optics, and mathematical physics;
→ *Stokes law*;
→ *Stokes parameter*. |

Stokes friction factor کروند ِ مالش ِ استوکس karvand-e mâleš-e Stokes
*Fr.: facteur de friction de Stokes*
For the translational motion of a spherical body moving in a
→ *viscous fluid*, the proportionality
factor between the uniform flow velocity far from the sphere and
the drag force, provided no-slip boundary condition and small
→ *Reynolds number*s:
*f* = 6πη*R*, where
η is the Reynolds number and *R* radius of the sphere. → *Stokes*; → *friction*;
→ *factor*. |

Stokes law قانون ِ استوکس qânun-e Stokes (#)
*Fr.: loi de Stokes*
1) *Fluid mechanics*: At low velocities, the frictional force on a
spherical body moving through a fluid at constant velocity is equal to
6π*R*η*v*, where *R* is the radius of the sphere,
η the fluid → *viscosity*, and *v* the velocity.
2) *Spectroscopy*: The wavelength of → *luminescence*
excited by radiation is
always greater than that of the exciting radiation. → *Stokes*; → *law*. |

Stokes parameters پارامونهای ِ استوکس pârâmunhâ-ye Stokes
*Fr.: paramètres de Stokes*
Four parameters which are needed to fully describe the
→ *polarization* state of
→ *electromagnetic radiation*.
They involve the maximum and minimum intensity, the ellipticity,
and the direction of polarization.
The four Stokes parameters are traditionally defined as follows:
*I* ≡ total intensity.
*Q* ≡ *I*_{0} - *I*_{90} =
difference in intensities between → *horizontal*
and → *vertical*
→ *linearly polarized* components.
*U* ≡ *I*_{+45} - *I*_{-45} =
difference in intensities between linearly polarized components
oriented at +45° and -45° (or 135°).
*V* ≡ *I*_{rcp} - *I*_{lcp} =
difference in intensities between right and left
→ *circularly polarized*
polarized components. → *Stokes*; → *parameter*. |