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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.
where ε is the average rate of dissipation of turbulence kinetic energy per unit mass, and; ν is the kinematic viscosity of the fluid.; Typical values of the Kolmogorov length scale, for atmospheric motion in which the large eddies have length scales on the order of kilometers, range from 0.1 to 10 millimeters; for smaller flows such as in laboratory systems, η may be much smaller.
The submultiple centistokes (cSt) is often used instead, 1 cSt = 1 mm 2 ·s −1 = 10 −6 m 2 ·s −1. 1 cSt is 1 cP divided by 1000 kg/m^3, close to the density of water. The kinematic viscosity of water at 20 °C is about 1 cSt.
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.
The values below 0 °C refer to supercooled water. Viscosity [11] 1.7921 mPa·s at 0 °C 0.5494 mPa·s at 50 °C 1.5188 mPa·s at 5 °C 0.5064 mPa·s at 55 °C 1.3077 mPa·s at 10 °C 0.4688 mPa·s at 60 °C 1.1404 mPa·s at 15 °C 0.4355 mPa·s at 65 °C 1.0050 mPa·s at 20 °C 0.4061 mPa·s at 70 °C 0.8937 mPa·s at 25 °C
The flow conditions must have a sufficiently small value of Reynolds number for there to be laminar flow. At 20 °C, the dynamic viscosity (kinematic viscosity × density) of water is 1.0038 mPa·s and its kinematic viscosity (product of flow time × factor) is 1.0022 mm 2 /s. These values are used for calibrating certain types of viscometers.
A critical value exists for the Rayleigh number, above which fluid motion occurs. [3] = The ratio of the Grashof number to the square of the Reynolds number may be used to determine if forced or free convection may be neglected for a system, or if there's a combination of the two.
There are many publications dedicated to numerical modeling of volume viscosity. A detailed review of these studies can be found in Sharma (2019) [15] and Cramer. [17] In the latter study, a number of common fluids were found to have bulk viscosities which were hundreds to thousands of times larger than their shear viscosities.