What is viscosity?
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When a fluid flows, internal friction within the fluid is generated due to the interactions between its flow layers, which gives the fluid its viscosity. Viscosity is a physical quantity that measures the degree of viscosity of a fluid. When measuring a fluid using a throttling device, it is necessary to know the fluid’s viscosity, mainly in order to calculate the Reynolds number, as the flow coefficient of the throttling device is related to the Reynolds number.
This post was last edited by pH7 on 2010-8-1 21:11. A brief addition: Viscosity is generally divided into dynamic viscosity and kinematic viscosity. Dynamic viscosity = shear stress/velocity gradient, with the unit P (g/cm·s). Kinematic viscosity = dynamic viscosity/density, with the unit St (cm2/s). Dynamic viscosity can also be expressed as the ratio of shear stress to shear rate. For Newtonian fluids, this is a constant, and the two are a straight line passing through the origin. For non-Newtonian fluids, it is either a straight line that does not pass through the origin, or a curve that passes through the origin. In petroleum refining and inorganic chemical industries, fluids are generally Newtonian. However, in fine chemical engineering, it is very likely to encounter non-Newtonian fluids. At that moment, I feel dizzy:dizzy:
As a supplementary note, the Reynolds number is a parameter that indicates the state of a fluid: values greater than 2300 indicate turbulent flow, while values less than 2000 indicate laminar flow. In the transitional zone between these values, throttle devices can only be used when the Reynolds number is within the turbulent flow range