ABSTRACT
This chapter defines viscosity as a property of a fluid. It analyses the torque required to overcome friction in a journal bearing. The chapter describes the behaviour of flow with friction and the use of the Reynolds number as a criterion for judging the nature of the flow.' It also defines the skin friction coefficient for flow with friction. The chapter examines the pressure drop associated with friction in pipes. A pressure drop is required to overcome friction in the flow. The friction is created due to the viscous nature of the fluid together with the nature of the flow. One characteristic of the behaviour of real flows with friction is that immediately adjacent to a solid surface the velocity of the flow is zero with respect to that surface. A boundary layer can be defined as the region of flow adjacent to a surface in which the flow velocity varies from zero to the free stream value.
