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For liquid, the dynamic viscosity is usually in the range of 0.001 to 1 Pascal-second, or 1 to 1000 centiPoise. 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 ...
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 is cP. The abbreviations cps, cp, and cPs are sometimes seen. Liquid water has a viscosity of 0.00890 P at 25 °C at a pressure of 1 atmosphere (0.00890 P = 0.890 cP = 0.890 mPa⋅s).
The SI unit of kinematic viscosity is square meter per second (m 2 /s), whereas the CGS unit for kinematic viscosity is the stokes (St, or cm 2 ·s −1 = 0.0001 m 2 ·s −1), named after Sir George Gabriel Stokes. [29] In U.S. usage, stoke is sometimes used as the singular form.
where (in SI units): is the frictional force – known as Stokes' drag – acting on the interface between the fluid and the particle (newtons, kg m s −2); 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);
1 reyn = 1 lb f s in −2. It follows that the relation between the reyn and the poise is approximately 1 reyn = 6.89476 × 10 4 P. In SI units, viscosity is expressed in newton-seconds per square meter, or equivalently in pascal-seconds. The conversion factor between the two is approximately 1 reyn = 6890 Pa s.
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.
millimetre of water (3.98 °C) mmH 2 O ≈ 999.972 kg/m 3 × 1 mm × g 0 = 0.999 972 kgf/m 2 = 9.806 38 Pa: pascal (SI unit) Pa ≡ N/m 2 = kg/(m⋅s 2) = 1 Pa [34] pièze (mts unit) pz ≡ 1000 kg/m⋅s 2 = 10 3 Pa = 1 kPa pound per square foot: psf ≡ 1 lbf/ft 2: ≈ 47.880 26 Pa [33] pound per square inch: psi ≡ 1 lbf/in 2: ≈ 6.894 757 ...
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 ...