The Poise (P) in Dynamic Viscosity

What is Poise (P)

Poise (P) is a unit of dynamic viscosity in the centimeter-gram-second (CGS) system. Dynamic viscosity measures a fluid's resistance to flow. The higher the dynamic viscosity, the thicker the fluid, meaning it flows less easily. Developed by French scientist Jean Léonard Marie Poiseuille in the 19th century, the poise is an important unit in various fields such as physics, engineering, and fluid dynamics.

Mathematically, 1 poise is defined as the viscosity of a fluid with a shear stress of 1 dyne per square centimeter (dyn/cm²) producing a shear rate of 1 reciprocal second (1/s). In equation form, this is shown as:

To give a sense of scale, the viscosity of water at room temperature is around 1 centipoise (cP), which is equivalent to 0.01 poise. This means water flows relatively easily compared to thicker fluids like honey or molasses, which have higher viscosity values.

Common Conversion Values

Understanding how poise relates to other units of dynamic viscosity is essential for practical applications. Here are some common conversion values:

• 1 (P) = 0.1 (Pa•s): The pascal-second (Pa•s) is the SI unit of dynamic viscosity. It provides a way to compare viscosities in scientific research and engineering.

• 1 (P) = 241.9088 (lb/(ft•h)): In the imperial system, viscosity can also be expressed in terms of pounds per foot per hour. This conversion is helpful in industries predominantly using imperial units.

• 1 (P) = 0.06719689 (lb/(ft•s)): Another imperial conversion expresses viscosity in pounds per foot per second. It highlights the significant differences in how viscosity is expressed across systems.

• 1 (P) = 0.002088543 (lbf•s/ft²): In some fluid mechanics applications, dynamic viscosity is expressed in terms of pounds-force seconds per square foot. This conversion can be particularly useful in engineering contexts.

• 1 (P) = 0.00001450377 (lbf•s/in²): For very precise applications dealing with small pressures, viscosity may be expressed in pounds-force seconds per square inch, showing how versatile dynamic viscosity measurements can be.

These conversions allow scientists, engineers, and technology specialists to work with viscosity in a way that suits their needs, whether they use the metric or imperial systems.