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The density is usually on the order of 1000 kg/m^3, i.e. that of water. Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes. For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to ...
The SI unit of dynamic viscosity is the newton-second per square meter (N·s/m 2), also frequently expressed in the equivalent forms pascal-second (Pa·s), kilogram per meter per second (kg·m −1 ·s −1) and poiseuille (Pl). The CGS unit is the poise (P, or g·cm −1 ·s −1 = 0.1 Pa·s), [28] named after Jean Léonard Marie Poiseuille.
The poise is often used with the metric prefix centi-because the viscosity of water at 20 °C (standard conditions for temperature and pressure) is almost exactly 1 centipoise. [3] A centipoise is one hundredth of a poise, or one millipascal-second (mPa⋅s) in SI units (1 cP = 10 −3 Pa⋅s = 1 mPa⋅s). [4] The CGS symbol for the centipoise ...
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
ρ p is the density of the particles (kg/m 3), ρ f is the density of the fluid (kg/m 3), μ is the (dynamic) fluid viscosity (Pa·s). Note that Stokes flow is assumed, so the Reynolds number must be small. A limiting factor on the validity of this result is the roughness of the sphere being used.
The poise (P) is a unit of dynamic viscosity equal to 1 Ba⋅s (100 mPa⋅s). [3] The stokes (St) is a unit of kinematic viscosity equal to 1 cm 2 ⋅s −1 (100 mm 2 ⋅s −1). [3] The stilb (sb) is a unit of luminance equal to 1 cd⋅cm −2 (10 kcd⋅m −2). [4] The phot (ph) is a unit of illuminance equal to 1 lm⋅cm −2 (10 klx). [3]
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μ is the dynamic viscosity of the fluid (Pa·s = N·s/m 2 = kg/(m·s)); Q is the volumetric flow rate, used here to measure flow instead of mean velocity according to Q = π / 4 D c 2 <v> (m 3 /s). Note that this laminar form of Darcy–Weisbach is equivalent to the Hagen–Poiseuille equation, which is analytically derived from the ...