3 - Fluid mechanics

Abstract

Fluid mechanics is the study of the behavior of liquids and gases, and particularly, the forces that they produce. This chapter discusses the fundamentals of engineering fluid mechanics in a general manner so that one can understand the way the forces are produced and transmitted by fluids that are, first, essentially at rest and, second, in motion. Hydrostatics, the study of fluids at rest, is a subject that is most commonly associated with civil engineers because of their interest in dams and reservoirs, but the subject is necessary for mechanical engineers too as it leads on to the subject of hydrodynamics, fluids in motion. This chapter looks at the subject of hydrostatic pressure variation with depth in a liquid, and uses the findings to explore the possibilities for measuring pressure with columns of liquids. It extends the study of hydrostatic pressure to the point where one can calculate the total force due to liquid pressure acting over a specified area. One of the main reasons for studying fluid mechanics in mechanical engineering is to make the calculation of the size of forces acting in a situation where liquids are employed, possible. Knowledge of these forces is essential so that a range of devices such as valves, pumps, fuel tanks and submersible housings can be designed safely. This allows the application of physical principles behind some of the most common applications of fluid mechanics in engineering.