Introduction

This introductory chapter comprises the basis and to a large extent is a guide for the rest of the book. It starts with a brief discussion of the history of the subject, which is followed by a number of various representative examples. The principal aim of bringing these examples is to demonstrate the variety of situations in which turbulent flows occur and the diversity of their manifestations. Where appropriate the examples are supplied by comments emphasizing the differences between turbulent and laminar flows and some specific properties of the former. Instead of a definition of turbulence a subsection is devoted to major qualitative universal properties of turbulent flows with cross references to the previous subsection on the representative examples. This is followed by a subsection attempting to give an idea as to why turbulence is such an extremely difficult problem. The last subsection contains an overview of the contents of the following chapters and the rest of the book.