Introduction

Abstract

The aim of this book is to provide the engineer and scientist with the necessary understanding of the underlying physics of turbulent flows, and to provide the user of turbulence models with the necessary background on the subject of turbulence to allow them to knowledgeably assess the basis for many of the state-of-the-art turbulence models. While a comprehensive review of the entire field could only be thoroughly done in several volumes of this size, it is necessary to focus on the key relevant issues which now face the engineer and scientist in their utilization of the turbulent closure model technology. The organization of this book is intended to guide the reader through the subject starting from key observations of spectral energy transfer and the physics of turbulence through to the development and application of turbulence models. Chapter 1 focuses on the fundamental aspects of turbulence physics. An insightful analysis of spectral energy transfer and scaling parameters is presented which underlies the development of phenomenological models. Distinctions between equilibrium and nonequilibrium turbulent flows are discussed in the context of modifications to the spectral energy transfer. The non-equilibrium effects of compressibility are presented with particular focus on the alteration to the turbulent energy dissipation rate. The important topical issue of coherent structures and their representation is presented in the latter half of the chapter. Both Proper Orthogonal Decomposition and wavelet representations are discussed. With an understanding of the broad dynamic With an understanding of the broad dynamic range covered by both the turbulent temporal and spatial scales, as well as their modal interactions, it is apparent that direct numerical simulation (DNS) of turbulent flows would be highly desirable and necessary in order to capture all the relevant dynamics of the flow. Such DNS methods, in which all the important length scales in the energy-containing range and in the dissipation range are accounted for explicitly is presented in Chapter 2. Emphasis is on spectral methods for incompressible flows, including the divergence-free expansion technique. Vortex methods for incompressible bluff body flows are described and some techniques for compressible turbulent flow simulations are also discussed briefly.