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Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. [1] For liquids, it corresponds to the informal concept of thickness; for example, syrup has a higher viscosity than water. [2]
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.
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 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3.
Symbol Name Meaning SI unit of measure nabla dot the divergence operator often pronounced "del dot" per meter (m −1) nabla cross the curl operator often pronounced "del cross" per meter (m −1) nabla: delta (differential operator)
Astronomical symbols – Symbols in astronomy; Chemical symbol – Abbreviations used in chemistry; Chinese punctuation – Punctuation used with Chinese characters; Currency symbol – Symbol used to represent a monetary currency's name; Diacritic – Modifier mark added to a letter (accent marks etc.)
After an example, he concludes (with used to represent volume viscosity): Hence, if the relaxation time of these processes is long, a considerable dissipation of energy occurs when the fluid is compressed or expanded, and, since this dissipation must be determined by the second viscosity, we reach the conclusion that ζ {\displaystyle \zeta ...
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.
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.