Kinematics of Fluid Flow, Parts I - V

To Start: Our goal in this opening section is to define what we mean by ’fluid flow’, a phrase we will use repeatedly, and to consider how a fluid flow is like and unlike solid particle dynamics. A second and more substantial goal is to erect a coordinate system that will be suitable for analyzing fluid flows quantitatively. The definition of a coordinate system is a matter of choice, and the questions to consider are more in the realm of kinematics than dynamics. Nevertheless, this definition of a coordinate system is a crucial step that is right at the heart of what makes fluid dynamics a challenging subject. In fact, the dynamics of the fluid flows that we will consider can be characterized as straightforward classical physics built upon the familiar conservation laws conservation of mass, (recti)linear momentum, angular momentum and energy and a few others. In this regard, the physics of fluid flow that we will consider are no different from the physics of classical, solid particle mechanics. However a fluid particle is in a literal sense pushed and pulled around by its surroundings (other fluid particles or boundaries) in a way that solid particles may not be (but this depends upon the phenomenon, of course). At the same time a fluid particle may be quite dramatically strained and stretched and become so inetermingled By coordinate system we mean something more fundamental than the ususal notion of Cartesian or curvilinear coordinates, for example.