It takes little more than a brief look around for us to recognize that fluid dynamics is one of the most important of all areas of physics—life as we know it would not exist without fluids, and without the behavior that fluids exhibit. The air we breathe and the water we drink (and which makes up most of our body mass) are fluids.
Motion of air keeps us comfortable in a warm room, and air provides the oxygen we need to sustain life. Similarly, most of our (liquid) body fluids are water based. And proper motion of these fluids within our bodies, even down to the cellular level, is essential to good health. It is clear that fluids are completely necessary for the support of carbon-based life forms.
But the study of biological systems is only one (and a very recent one) possible application of a knowledge of fluid dynamics. Fluids occur, and often dominate physical phenomena, on all macroscopic (non-quantum) length scales of the known universe—from the megaparsecs of galactic structure down to the micro and even nanoscales of biological cell activity. In a more practical setting, we easily see that fluids greatly influence our comfort (or lack thereof); they are involved in our transportation systems in many ways; they have an effect on our recreation (e.g., basketballs and footballs are inflated with air) and entertainment (the sound from the speakers of a TV would not reach our ears in the absence of air), and even on our sleep (water beds!).
From this it is fairly easy to see that engineers must have at least a working knowledge of fluid behavior to accurately analyze many, if not most, of the systems they will encounter.
LECTURES IN ELEMENTARY
Physics, Mathematics and Applications
J. M. McDonough