If the viscosity is very high, for instance in pitch, the fluid will appear to be a solid in the short term. Otherwise all fluids have positive viscosity. Zero viscosity is observed only at very low temperatures, in superfluids. A fluid that has no resistance to shear stress is known as an ideal fluid or inviscid fluid. La formula del numero di Reynolds (Re) è la seguente: Re p (v) d / u, dove p è la massa volumica (kg/m al cubo), v è la velocità macroscopica (m/s), d è una grandezza che. A liquid's viscosity depends on the size and shape of its particles and the attractions between the particles. La viscosità cinematica dipende dal tipo di fluido e può essere ottenuta da tabelle o calcolata in base alla viscosità dinamica e alla densità del fluido. For the same velocity pattern, the stress required is proportional to the fluid's viscosity. When the fluid is forced through a tube, the fluid generally moves faster near the axis and very slowly near the walls therefore, some stress is needed to overcome the friction between layers and keep the fluid moving. Viscosity is due to the friction between neighboring particles in a fluid that are moving at different velocities. For example, honey has a much higher viscosity than water.
For liquids, it corresponds to the informal notion of 'thickness'.
Viscosity The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress.
