FLOW OF LIQUIDS : fluid mechanics (mechanical engineering)

A fluid at rest experiences no shear force. When in motion, though, shear forces can be set up due to viscosity and ‘turbulence’ which oppose motion, producing a ‘frictional’ effect. A fluid consists of a large number of individual particles moving in the general direction of flow but usually not parallel to each other. The path followed by a particle is called a path line. A pathline (or particle path) is the trajectory of an individual element of fluid. At any given instant of time the positions of successive particles can be joined up by a curve which is tangential to the direction of motion of the particle at that instant. This curve is called a streamline. A streamline is a continuous line within a fluid such that the tangent at each point is the direction of the velocity vector at that point. When considering the flow of a large body of fluid it is sometimes convenient to consider a small section. If streamlines are drawn through every point on the circumference of a small area they form a stream tube. 1.1 Flow Visualization Since the velocity of a particle at any point on a streamline is tangential to it, there can be no flow across a streamline...