Conversion of Kinematic Viscosity SI units

Introduction to Kinematic Viscosity

Kinematic viscosity (or dynamic viscosity divided by density) is a physical property of a liquid used to measure its resistance to flow. In other words, kinematic viscosity is used to measure the amount of internal friction in a liquid, allowing us to predict how it will move or diffuse in a closed system. It is expressed in terms of a number and has been measured in a variety of units, the most common of which are the square meter per second (m²/s).

History and Origins of Kinematic Viscosity Units

Kinematic viscosity units were first created in the late 19th century by physicist Lord Rayleigh. His work focused on the literal measurement of viscosity, which allows for the calculation of kinematic viscosity from the ratio of viscosity to density. Since then, many other unitary systems have been used to measure kinematic viscosity, including square centimeters per second (cm²/s), Stokes (St), square feet per second (ft2/s) and square inches per second (in²/s). More recently, units based on time have been developed, including square meters per hour (m²/h), square centimeters per hour (cm²/h), square feet per hour (ft²/h) and square inches per hour (in²/h).

Examples of Kinematic Viscosity Values

Below is a list of reference and record values in the different units of kinematic viscosity, including:

• Square meter per second (m²/s): Water at 20°C has a kinematic viscosity of approximately 1.0 × 10^-6 m²/s.
• Square centimeter per second (cm²/s): Water at 20°C has a kinematic viscosity of approximately 1.0 × 10^-2 cm²/s.
• Stokes (St): Water at 20°C has a kinematic viscosity of approximately 1.0 × 10^-4 St.
• Centistokes (cSt): Water at 20°C has a kinematic viscosity of approximately 1.0 cSt.
• Square foot per second (ft²/s): Water at 68°F has a kinematic viscosity of approximately 1.13 × 10^-5 ft²/s.
• Saybolt Universal Second (SUS): SAE 30 oil at 100°F has a kinematic viscosity of approximately 295 SUS.
• Redwood Second (Rd): Fuel oil at 100°F has a kinematic viscosity of approximately 200 Rd.
• Engler Degree (°E): Water at 20°C has a kinematic viscosity of approximately 0.0017 °E.

How to Convert Kinematic Viscosity Units

Kinematic viscosity units can be converted from one system to another, depending on the need or desired output. Generally, the conversion process involves multiplying the unit by the appropriate conversion factor. For example, to convert m²/s to cm²/s, one would multiply the number by 10,000. Similarly, to convert m²/h to ft²/h, one would multiply the number by 0.3117.

Conclusion

Kinematic viscosity is an important measure of a liquid’s response to flow, and many units have been developed to gauge this property, some of which are time-dependent. Reference and record values of kinematic viscosity have been measured in all of these units, and the conversion process between them is quite straightforward.