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It is a special case of the general definition of viscosity (see below), which can be expressed in coordinate-free form. Use of the Greek letter mu ( μ {\displaystyle \mu } ) for the dynamic viscosity (sometimes also called the absolute viscosity ) is common among mechanical and chemical engineers , as well as mathematicians and physicists.
The poiseuille (symbol Pl) has been proposed as a derived SI unit of dynamic viscosity, [1] named after the French physicist Jean Léonard Marie Poiseuille (1797–1869).. In practice the unit has never been widely accepted and most international standards bodies do not include the poiseuille in their list of units.
(dynamic) viscosity (also ) pascal second (Pa⋅s) theta: angular displacement: radian (rad) kappa: torsion coefficient also called torsion constant newton meter per radian (N⋅m/rad) lambda: cosmological constant: per second squared (s −2)
Micrometre or micron (retired in 1967 as a standalone symbol, replaced by "μm" using the standard SI meaning) the coefficient of friction in physics; the service rate in queueing theory; the dynamic viscosity in physics; magnetic permeability in electromagnetics; a muon; reduced mass; the ion mobility in plasma physics
The poise (symbol P; / p ɔɪ z, p w ɑː z /) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units (CGS). [1] It is named after Jean Léonard Marie Poiseuille (see Hagen–Poiseuille equation). The centipoise (1 cP = 0.01 P) is more commonly used than the poise itself.
μ (some authors use the symbol η) is the dynamic viscosity (Pascal-seconds, kg m −1 s −1); R is the radius of the spherical object (meters); is the flow velocity relative to the object (meters per second). Note the minus sign in the equation, the drag force points in the opposite direction to the relative velocity: drag opposes the motion.
Dynamic viscosity is a material property which describes the resistance of a fluid to shearing flows. It corresponds roughly to the intuitive notion of a fluid's 'thickness'. For instance, honey has a much higher viscosity than water. Viscosity is measured using a viscometer. Measured values span several orders of magnitude.
Common symbols are , ′,, or . It has dimensions (mass / (length × time)), and the corresponding SI unit is the pascal -second (Pa·s). Like other material properties (e.g. density , shear viscosity , and thermal conductivity ) the value of volume viscosity is specific to each fluid and depends additionally on the fluid state, particularly ...