Viskøs

Viskøs is a Norwegian adjective meaning viscous, used to describe a fluid with a high resistance to flow due to internal friction. In science and engineering, viscosity is a property that quantifies this resistance.

Dynamic viscosity, denoted by η, measures the tangential stress needed to produce a given rate of shear in a fluid. It is expressed in pascal-seconds (Pa·s). For Newtonian fluids, η is approximately constant over a range of shear rates; for non-Newtonian fluids, viscosity can change with shear rate, temperature, or time. Kinematic viscosity, denoted by ν, is the ratio of dynamic viscosity to density (ν = η/ρ) and has units of m^2/s, commonly given in Stokes (St) or centistokes (cSt) (1 St = 1 cm^2/s = 1×10^-4 m^2/s; 1 cSt = 1×10^-6 m^2/s).

Temperature strongly affects viscosity: increasing temperature generally lowers viscosity. Common examples include water, which has a low viscosity around 1 mPa·s (0.001 Pa·s) at room temperature, and honey, which is much more viscous (ranging from about 2 to 10 Pa·s depending on temperature and composition).

Measurement methods include capillary viscometers and rotational viscometers, which determine η under controlled conditions of temperature and shear rate. Viscosity is a key parameter in applications such as lubrication, paints and coatings, food processing, cosmetics, and polymer processing, influencing flow, mixing, heat transfer, and film formation.

In Norwegian usage, viskøs describes the property itself, while viskositet refers to the characteristic of a substance. The term also appears in everyday language to describe thick, sticky liquids or gels.