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The centipoise is convenient because the viscosity of water at 20 °C is about 1 cP, and one centipoise is equal to the SI millipascal second (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 ...
For kinematic viscosity, the SI unit is m^2/s. In engineering, the unit is usually Stoke or centiStoke, with 1 Stoke = 0.0001 m^2/s, and 1 centiStoke = 0.01 Stoke. 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.
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).
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.
where μ = effective viscosity in centipoise ρ = density in g/cm 3 t = quart funnel time in seconds For example, a mud of funnel time 40 seconds and density 1.1 g/cm 3 has an effective viscosity of about 16.5 cP. For the range of times of typical muds above, the shear rate in the Marsh funnel is about 2000 s −1. [4]
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.
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
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 its temperature and pressure .