Viscosity in physics is one of the properties of matter whereby the motion of molecules with respect to surrounding molecules encounters, due to intermolecular forces, a resistant force: in solids it is highest, but lowest in liquids and gases. If we immerse a foreign body in the fluid under consideration, it will encounter a resistance whose strength varies depending on the fluid’s degree of viscosity.
Molasses, for example, has a higher viscosity than water because it is more resistant to flow.
There are many methods one can use to measure the viscosity of a fluid, the easiest and most straightforward being to drop a sphere of a certain diameter into a transparent container containing the fluid whose viscosity one is trying to determine.
ATTENTION: the reciprocal of viscosity is called fluidity, a measure of smoothness.
Viscosity is an important factor in determining the forces that must overcome when liquids are used for lubrication and transported in pipes. It will therefore be important for us to understand what type of fluid the Besa® valve will be working with, as the friction between the walls of a pipe and the fluid flowing through it affects the valve’s discharge performance.
It controls fluid flow in processes such as spraying, injection moulding and surface coating.
Let us consider two planes, separated by a fluid (temperature controlled) and parallel to each other, one stationary and the other subjected to a force that pushes/pulls it parallel to the other plane.
Depending on the fluid we use to separate the two planes, and always applying the same force to move one of the two planes, we will find that the velocity of the plane varies depending on the fluid we have chosen.
The tangential force will be inversely proportional to the distance between the two planes and directly proportional to the speed.
Introducing the velocity term complicates things, because only theoretically is the variation in velocity linear.