An Introduction to Fluid Mechanics pp 31-57 | Cite as

# Fundamental Concepts

## Abstract

Fluids at rest or in motion exhibit distinct characteristics from those of solids. Fundamental concepts which are essential to the understanding of fluid motions are explored in this chapter. First, distinctions between common fluids and solids with their underlying physical features are discussed. The Deborah number is introduced in order to take into account the rheological characteristics of matter under different external excitations. Equations in applied mechanics and fluid mechanics are classified into two categories to demonstrate their intrinsic features, followed by the method of analysis used in describing physical process. The assumption of fluid as a continuum plays a crucial role in defining fluid properties, with which theory of fluid motions may be established. Among the properties of a fluid are the viscosity and pressure relatively important. While the former is explored by using Newton’s law of viscosity, the latter is discussed by using Pascal’s law. Characteristics of fluid flows such as ideal flows versus viscous flows, incompressible flows versus compressible flows, and laminar flows versus turbulent flows are introduced, with their detailed discussions provided in the forthcoming chapters. A structural classification is given at the end to show the main topics of the book, which will be discussed separately in different chapters.

## Further Reading

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