ABSTRACT
This chapter considers the somewhat more interesting flows in which velocity gradients and accelerations do appear. The velocity field specifies the instantaneous speed and direction of the motion of all points in the flow. A streamline is everywhere tangent to the velocity field and so reflects the character of the flow field. Streamlines can give us important information about the pattern and relative speed of flow. Closely spaced streamlines reflect faster flow than widely spaced streamlines. There is no flow across or through streamlines, since the velocity field is purely tangential to these lines. The principle of mass conservation is fundamental to the study of mechanics. It states that mass is neither created nor destroyed; hence, the mass of a system remains constant as the system moves through the flow field. Viscous effects are generally negligible far from flow boundaries, allowing us to rely on Euler’s inviscid momentum equation in good faith.
