Dyno: Dynamics

Abstract

Dynamics, which is abbreviated as dyno in this book, is a relatively ambiguous concept in multiphysics. In this book, acoustics as the study of mechanical waves is viewed as a special case of dynamics, consisting of both a part of elastodynamics and a part of fluid dynamics. Meanwhile, the wave theory discussed in acoustics is also considered as part of the general wave theory which also covers waves other than mechanical waves. Due to the consideration, in this chapter, elastodynamics will be introduced first, in which we will show that the governing equation of elastodynamics directly describes the mechanical waves in solids. Then we will use two different ways to show that the wave equation for the acoustics in fluids can be derived as a special case (or a derivative) of fluid dynamics via the Navier-Stokes equation. The wave equation generalized from acoustics will be discussed next. In the end, a practice problem will be provided to show the idea and implementation of elastodynamics. Fluid dynamics, which is treated as a multiphysical field, will be introduced in the next part of the book.