Viscosity is the resistance produced in a liquid to its flow. Viscosity is an essential feature of liquids that are used for lubrication, like lubricating oils and grease. The generalized expression in coordinate-free form is provided by.
Where \, which is a particular case of fluid viscosity. The force F acting on the fluid particles is directly proportional to the fluid velocity ‘u’ and the area ‘A’ of the layer and is inversely proportional to the distance ‘y’ between them.Īccording to Newton, the viscosity formula is, In fluids, the flow velocity varies linearly at different points, being 0 at the bottom, and a velocity ‘u’ in the top. Sir Isaac Newton has postulated some assumptions regarding the fluid viscosity. Let us consider a liquid in which the fluid particles move in a specific direction in straight parallel lines. This makes it difficult for a user to decide the instrument type while experimenting with accurate measurement. Many different types are available for viscosity measurements simple ones involve counting of seconds as a liquid drop from a stick, while complex instruments involve sophisticated automatic recordings. Selecting the right viscometer that suits your experiment is quite a difficult task. There are various methods to measure viscosity, depending upon the type of materials used and the circumstances. This is the reason that fluids with high viscosity need more force to move as compared to those of low viscosity. Shearing occurs when a fluid moves or is distributed, like pouring, spraying, spreading, mixing, etc. More is the friction more is the amount of force required to move the layers this is called shear. The internal forces or friction of fluid comes into play when one layer of fluid is subjected to move over another layer.
It is a measure of the internal forces of a fluid. Viscosity is the tendency of a fluid to resist any change in its shape or motion.
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