Introduction

Abstract

Turbulent flows occur in many processes in nature as well as in many industrial applications. A storm, for instance, is accompanied with a wind which has a high velocity and can change its direction and also its speed abruptly. The take-off of an aircraft leads to turbulent air above the runway which has to be calmed down before the start of the next aircraft. This necessary interval between the take-offs of the aircrafts limits the number of starts in a given time period. There are many more examples of turbulent flows, e.g., in oceanography and in wind channels for the design of cars. Often, turbulent flows go along with chemical reactions like in gas engines. A wide variety of other examples for turbulent flows can be found, e.g., in the book by Lesieur [Les97, Chapter I].