Difference between kinematic viscosity and dynamic viscosity (Conversion of kinematic viscosity and dynamic viscosity)
I. The difference between kinematic viscosity and dynamic viscosity
Kinematic viscosity (kinematic viscosity) and dynamic viscosity (dynamic viscosity) are two descriptions of liquid viscosity or flow properties of different physical properties, the difference is as follows:
1, the difference between the two definitions
Kinematic viscosity: kinematic viscosity refers to the viscosity of the liquid and its density ratio, usually with Heathcock (cSt) or square centimeters / second (cm²/ s) as a unit of expression. It indicates the amount of liquid flowing through a unit area in a unit of time, usually used to describe the viscosity of the liquid at rest.
Dynamic viscosity: dynamic viscosity is the viscosity of the liquid, usually in Pascal seconds (Pa-s) or Poise as the unit of expression. It indicates that the liquid resistance to flow, usually used to describe the viscosity of the liquid in the flow state.
2, The difference between the calculation relationship
Kinematic viscosity (ν) is equal to the dynamic viscosity (η) divided by the density of the liquid (ρ), that is: ν = η / ρ.
Dynamic viscosity (η) is equal to the kinematic viscosity (ν) multiplied by the density of the liquid (ρ), that is: η = ν * ρ.
3. Difference in use
Kinematic viscosity is usually used to analyze the flow properties of liquids in flowing pipelines, such as the pressure drop calculation of liquids in conveying pipelines and the evaluation of lubrication performance of liquids in lubrication systems.
Dynamic viscosity is usually used to describe the viscosity of the liquid in the flow state, for example, in fluid dynamics, used to describe the liquid resistance and viscous resistance, as well as the flow characteristics of the liquid under the action of force.
Both kinematic viscosity and dynamic viscosity relate to the viscosity or flow properties of a liquid, but they have different units and application scenarios. Kinematic viscosity is usually used to describe the viscosity of a stationary liquid, while dynamic viscosity is used to describe the viscosity of a flowing liquid. They are related to each other through the density of the liquid.
II. The kinematic viscosity and dynamic viscosity conversion relationship
Kinematic viscosity (kinematic viscosity) and dynamic viscosity (dynamic viscosity) between the conversion relationship can be expressed by the following formula:
Dynamic viscosity (η) = kinematic viscosity (ν) × density (ρ)
which:
Dynamic viscosity (η) to Pascal seconds (Pa-s) or Poise (Poise) as a unit.
Kinematic viscosity (ν) is measured in square centimeters per second (cm²/s) or cSt.
Density (ρ) is usually measured in kilograms per cubic meter (kg/m³).
To convert units, use the above formula to convert kinematic viscosity to dynamic viscosity or vice versa. It is important to note that to make the conversion, the density value of the liquid needs to be known. The density value can be determined based on the type of liquid and the temperature, since density varies with temperature.
Example:
Assuming there is a liquid with a kinematic viscosity of 100 cSt and a density of 900 kg/m³, it can be converted to a kinetic viscosity using the above equation:
Kinetic viscosity (η) = 100 cSt × (900 kg/m³ / 1000) = 90 Pa-s
Therefore, the kinetic viscosity of the liquid is 90 Pa-s. Density values will vary depending on the liquid and temperature, so be sure to use the correct density value when making the conversion.
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