viskosite

Viskosite, often spelled viscosity, is a fundamental property of fluids that describes their resistance to flow. Imagine honey versus water; honey is much more viscous than water because it flows more slowly. This resistance arises from the internal friction between the fluid's molecules. When a fluid is in motion, different layers of the fluid move at different speeds, and the intermolecular forces between these layers create a drag, or friction, that opposes this relative motion.

The SI unit for dynamic viscosity is the Pascal-second (Pa·s), though the centipoise (cP) is also commonly used, where 1 Pa·s = 1000 cP. Kinematic viscosity, which relates dynamic viscosity to density, is measured in square meters per second (m²/s) or centistokes (cSt). Temperature significantly affects viscosity: for most liquids, viscosity decreases as temperature increases, as molecules have more energy to overcome intermolecular forces. Conversely, for gases, viscosity generally increases with temperature due to increased molecular collisions.

Viscosity plays a crucial role in numerous scientific and engineering applications, from designing pipelines and lubrication systems to understanding blood flow and weather patterns. It's a key parameter in fluid mechanics, influencing how fluids behave under pressure, shear, and other forces.