Chapter 5 : Equations of Motion and Mechanical Energy
Lecture 14 :

 Losses Due to Geometric Changes In case of flow of a real fluid, the major source for the loss of its total mechanical energy is the viscosity of fluid which causes friction between layers of fluid and between the solid surface and adjacent fluid layer. Loss of Energy It is the role of friction, as an agent, to convert a part of the mechanical energy into intermolecular energy. This part of the mechanical energy converted into the intermolecular energy is termed as the loss of energy. When the path of the fluid is suddenly changed in course of its flow through a closed duct due to any abrupt change in the geometry of the duct then apart from the losses due to friction between solid surface and fluid layer past it, the loss of mechanical energy is also incurred. In long ducts, these losses are very small compared to the frictional loss, and hence they are often termed as minor losses. But minor losses may, however, outweight the friction loss in short pipes or ducts. The source of these losses is usually confined to a very short length of the duct, but the turbulence produced may persist for a considerable distance downstream. Example of some minor Loss We'll discuss them individually in the next consequent slides