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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Wall turbulence control is a major subject, the investigation of which involves significant industrial, environmental and fundamental consequences. Wall Turbulence Control addresses recent advances achieved in active and passive wall turbulence control over the past two decades. This valuable reference for scientists, researchers and engineers provides an updated view of the research into this topic, including passive control, optimal and suboptimal control methodology, linear control and control using adaptive methods (neural networks), polymer and bubble injection, electromagnetic control and recent advances in control by plasma.
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Seitenzahl: 241
Veröffentlichungsjahr: 2017
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Table of Contents
Cover
Title
Copyright
Preface
Notations
1 General Points
1.1. Introduction
1.2. Tools to analyze and develop control strategies
2 Summary of the Main Characteristics of Wall Turbulence
2.1. Introduction
2.2. General equations
2.3. Notations
2.4. Reynolds equations
2.5. Exact relations and FIK identity
2.6. Equations for a turbulent boundary layer
2.7. Scales in a turbulent wall flow
2.8. Turbulent viscosity closures
2.9. Turbulent intensities of the velocity components
2.10. Vorticity and near wall coherent structures
3 Passive Control
3.1. Introduction
3.2. Large eddy (outer layer) breakup devices, LEBUs (OLDs)
3.3. Riblets
3.4. Superhydrophobic surfaces
4 Active Control
4.1. Introduction
4.2. Local blowing
4.3. Ad-hoc control
4.4. Transverse wall oscillations
4.5. Alternated spanwise Lorenz forcing and electromagnetic (EM) control
4.6. Extensions of spanwise forcing
4.7. Reynolds number dependence
4.8. Suboptimal active control
4.9. Optimal active control
4.10. Optimal linear control
4.11. Neural networks
4.12. Stochastic synchronization of the wall turbulence and dual control
Bibliography
Index
End User License Agreement
List of Tables
1 General Points
Table 1.1.
Required characteristics of pressure sensors in wall bounded turbulent flows at a small-moderate Reynolds number
Table 1.2.
Required characteristics of wall shear-stress sensors in wall bounded turbulent flows at a small-moderate Reynolds number
Guide
Cover
Table of Contents
Begin Reading
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Wall Turbulence Control
Sedat Tardu
First published 2017 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd
27-37 St George’s Road
London SW19 4EU
UK
www.iste.co.uk
John Wiley & Sons, Inc.
111 River Street
Hoboken, NJ 07030
USA
www.wiley.com
© ISTE Ltd 2017
The rights of Sedat Tardu to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.
Library of Congress Control Number: 2016959098
British Library Cataloguing-in-Publication Data
A CIP record for this book is available from the British Library
ISBN 978-1-84821-559-7
Preface
This short book is devoted to turbulent skin-friction control.
Reducing drag by only a few percent in transport vehicles (motor cars, aircraft, ships, etc.) would achieve a saving of tens of billions of Euros per year in fuel, and a significant reduction of the human impact on the environment. In the context of a civil or commercial transport aircraft, depending on the size, viscous or skin friction drag accounts for about 40–50% of the total drag under cruise conditions A cut in skin friction drag by 20% applied only to all commercial aircraft operating in the European Community would cut fuel consummation by about 30 million tones a year, corresponding to some 5–10% of total fuel consumption. This also corresponds to a reduction of several million tons of CO2 emissions annually. It is also important to recall the main goals of the vision 2020 launched by the European commission: a 50% cut in CO2 emissions per passenger kilometer. Environmental factors, such as noise, and impact on climate change, also have to be underlined. At present, the implementation of feasible, effective skin-friction control strategies is a long way from becoming a reality. It requires an in-depth knowledge of near-wall turbulence, which in spite of the considerable advances made during recent decades, is not yet at a sufficient level.
From a fundamental point of view, the management of the nonlinearity inherent in the Navier–Stokes equations coupled with the complexity induced by the presence of the wall is a formidable challenge for the researchers.
The aim of this book is to give a short overview of the turbulent skin-friction research conducted up until now; however, in spite of the effort invested in its preparation, it is far from being exhaustive. Only a limited part of the very broad literature on the subject could be analyzed in this book. I must say that it is difficult to avoid a certain degree of subjectivity in the presentation of the existing control approaches, although I have tried to be as objective as possible.
The book contains four chapters. A general introduction is given in Chapter 1 wherein the key elements related to the tools necessary to develop control strategies, such as numerical simulations, micro sensors and actuators, are briefly discussed. The aim of Chapter 2 is to provide the reader with a short and concentrated review of the basic structural elements of wall turbulence. Passive control strategies are discussed in Chapter 3 that concentrate only on large eddy breakup devices, riblets and superhydrophobic surfaces. Active control of skin friction drag is the subject of Chapter 4, which aims to present the huge progress achieved in the domain over the last decades.
First and foremost, I would like to extend my thanks to my former PhD students, Olivier Doche, François Bouillon, Stéphane Montesimo and Frédéric Bauer, without whom I could certainly not undertake research in the fascinating area of flow control. Writing a book requires time. My heartfelt thanks go to my wife, Carmel, for her unfailing support, and to my sons, Aran, Noah and Teoman, for their patience.
Sedat TARDUNovember 2016
Notations
C
f
drag coefficient
D/Dt
material derivative
H
shape factor
h
half-height of the channel
k
x
streamwise wavenumber
k
z
spanwise wavenumber
ℓ
mixing length
mean pressure
p
fluctuating pressure
shear velocity
U
i
local instantaneous velocity
mean streamwise velocity
mean wall-normal velocity
mean spanwise velocity
velocity outside of the boundary layer
velocity at the channel centerline
bulk velocity
Re
Reynolds number
Re
τ
Reynolds number based on the shear-stress rate and the outer scale (von Kárman number)
Re
θ
Reynolds number based the momentum thickness and the velocity outside of the boundary layer (or velocity in the center of a channel)
W
c
Coles’ wake function
u,u
1
streamwise fluctuating velocity
v, u
2
wall-normal fluctuating velocity
w, u
3
spanwise fluctuating velocity
Reynolds shear stress (for the simplicity’s sake, the correlation is sometimes also called the Reynolds correlation)
t
time
x, x
1
streamwise coordinate
y, x
2
wall-normal coordinate
z, x
3
spanwise coordinate
v
ko
Kolmogorov velocity scale
Subscript and superscript notation
( )
i
velocity or vorticity component
( )
w
or ( )
0
quantity at the wall
mean of a fluctuating physical quantity
Fourier transform
( )
+
quantity rendered dimensionless by the inner scales and
ν
Vectorial operators
and the Einstein summation convention applies
divergence
•
scalar product
Greek symbols
δ
ij
Kronecker delta
δ
boundary-layer thickness
δ
d
displacement thickness
δ
v
viscous sublayer thickness
δ
R
Rotta thickness
η
K
0
Kolmogorov length scale
κ
von Kárman constant
Λ
0
outer length scale
ν
kinematic viscosity
ν
t
turbulent viscosity
μ
dynamic viscosity
ν
kinematic viscosity
mean vorticity component
i
mean spanwise vorticity
ω
i
instantaneous local vorticity component
i
ω
x
, ω
y
, ω
z
instantaneous local components of streamwise, wall-normal and spanwise vorticity
Π
Coles’ wake factor
ρ
density
σ
ij
stress tensor
mean square value of fluctuations in wall shear stress in the streamwise direction
mean square value of fluctuations in wall shear stress in the spanwise direction
mean square values of fluctuations in streamwise, wall-normal and spanwise vorticity
θ
momentum thickness
mean wall shear stress
fluctuations of wall shear stress in the streamwise direction
fluctuations of wall shear stress in the spanwise direction
