Some common viscosities are listed in this chart: In common vernacular, a liquid is said to be “viscous” if its viscosity is substantially greater than that of water, and is described as “mobile” if the viscosity is noticeably less than water. Some liquids, like pitch, glass and peanut butter, have such high viscosity they behave like solids. Fluids with low viscosity have a low resistance and shear easily and the molecules flow quickly high viscosity fluids move sluggishly and resist deformation. Pressure or energy (“stress”) is needed to overcome the friction between the faster-moving fluid and the more slowly moving layers. This is because of the friction with the walls. For example, when a fluid flows through a tube, the fluid will move more quickly near the center of the tube axis but move more slowly along the walls of the tube. This corresponds to the informal concept of “thickness” - for example, honey is thicker and has a much higher viscosity than water.Īccording to Wikipedia, viscosity is the friction between the molecules of fluid.
Chemists have a slightly different feel for the phenomenon viscosity is defined as its resistance to gradual deformation. Most people think of “viscosity” in terms of a fluid’s ability to flow. Fluid mechanics is the study of how fluids move, and one of the most important parameters of fluids is their viscosity.
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