Table Of ContentTURBULENCE CONTROL BY PASSIVE MEANS
FLUID MECHANICS AND ITS APPLICATIONS
Volume 4
Series Editor: R. MOREAU
MADYLAM
Ecole Nationale Superieure d' Hydraulique de Grenoble
Boite Postale 95
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Aims and Scope of the Series
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As well as the more traditional applications of aeronautics, hydraulics, heat and
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in a state of rapid development, such as turbulence, suspensions and multiphase
fluids, super and hypersonic flows and numerical modelling techniques.
It is a widely held view that it is the interdisciplinary subjects that will receive
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For a list of related mechanics titles, seefinal pages.
Turbulence Control
by Passive Means
Proceedings of the 4th European Drag Reduction Meeting
edited by
E. COUSTOLS
ONERAICERT,
Toulouse Cedex,
France
KLUWER ACADEMIC PUBLISHERS
DORDRECHT I BOSTON I LONDON
ISBN-13: e-ISBN-13:
DOl: 10.1007/
Library of Congress Cataloging in Publication Data
European Drag ReductIon Meeting (4th 1989 Lausanne. Switzerland)
Turbulence control by passIve means proceedings of the Fourth
European Drag Reduction MeetIng ! edIted by E. Coustols.
p. cm.
"The ~ourth European Drag Reduction Meeting was held. July 24.
1989 in Lausanne. Switzerland."
Incluces olbl1ographical references and index.
ISBN 0-7923-1020-9
F1Lla dynamlcs--Congresses. 2. Turbulent boundary layer-
I.
-Congresses. I. Coustols. E. II. Title.
TA357.5.T87E93 1989
620.1 '064--jc2G 90-48907
ISBN-13: 978-94-010-7471-1 e-ISBN-13: 978-94-009-2159-7
001: 10.1007/978-94-009-2159-7
Published by Kluwer Academic Publishers,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
Kluwer Academic Publishers incorporates
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D. Reidel, Martinus Nijhoff, Dr W. Junk and MTP Press.
Sold and distributed in the U.S.A. and Canada
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101 Philip Drive, Norwell, MA 02061, U.S.A.
In all other countries, sold and distributed
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Printed on acid-free paper
All Rights Reserved
© 1990 by Kluwer Academic Publishers
Softcover reprint of the hardcover 1s t edition 1990
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
Contents
Preface vii
Final programme ix
External Manipulators (LEEUs)
Balallce of turbulent kinetic energy downstream a single flat plate Inaniplllator :
comparisons betll'een detailed experiments and modelling. C. Tf 1/ a ud. I run ny.
IP. Bonnet C' I Dclville
.\Ianipulation and modelling of turbulent pipe flow: some parametric studies of
single and tandem ring devices. A. Pollard. H. Thoma n 11 C A .Jl. SUl'ili 23
Large eddy simulation of manipulated boundary layer and channel flows. 11.
1,'hin C' R. Friedrich -\1
The importance of LEBF de\'ice shape [or turbulent drag reduction.A. Butril"ud f,7
Internal Manipulators (Riblets)
Boundary layer flO\\' visualisation patterns on a riblet surface. JJ C. C/n Ik 7')
Simultaneous flow \'isualisation and LDA studies over longit uclillallllicro-grom'ecl
surfaces. C.I.l. Pulles. K.K. Prasad () F. T..U. "YiuUL'stailt LJ7
Effects of longitudinal pressure gradients on turbulent drag reduction with riLkts.
1,'.S. Choi IOl)
Synthesis of experimental riblet studies in transonic conditions. E. COI/sto/.' C
IT. Schmitt 12.\
Effect of ri blet s on either fully dewloped boundary layers or illt ernal flo\\"" ill
laminar regime. I Liandrat. E. COllslo/s. L. Djenidi. F. Ansc/})ut. )( de SO/III-
\'iclol'. F. Fioc [;' L. Fu/achier 1-\1
Internal and External 1\1anipulators
Turhulent houndar\' layer OHT a ribleted surfClce with tandelll l11i111ipulators 1),
ing surfac(' drag balances. I'.D ..Y gllycn. I Dickinson. }'. .]U/II. L Cha/Irollr. "I.
Small!. A. Pogc C F. PaquEt 15')
List of referees In
Preface
In the last decades, a lot of effort has been directed towards manipulation of
turbulent boundary layers by passive devices such as external manipulators (thin
flat plates or aerofoil section devices embedded in the outer layer) and/or internal
manipulators (small streamwise grooves acting directly on the inner region) for the
purpose of reducing viscous drag. The former are commonly referred to as LEI3U s or
BLADEs and the laHer riblets or grooves. Though the details of the mechanisms are
not firmly understood, world-wide experimenta.! data are available and consistent
enough in order to assert the potential of such devices for turbulent drag reduction.
It should be noted that following on from recent and successful flight tests, the
concept of using grooved surfaces is rather close to finding industrial applications.
During the last few years, in Europe, there has been considerable interest in
lookillg at the behaviour of such passi,'e turbulence manipulators. A lot of intense
research, concerning both experimental and theoretical studies. has been carried out
in some European research centres. For the last fi\'e years. informal gatherings. called
,.\ \'orking Pi\l'ty i\Ieetings" , have been set up, once a year; the aim of these meetings
is not only to bring together European researchers acti,'e in the field of turbulent
drag reduction by passi"e means and to hear about recent de\'c!opments but also to
o u t1 ine sui tit ble directions for future research or collaborative programmes.
Thus, follO\\'ing on from previous meetings at EPF Lausanne (September 1st
:3rd, 1986), ONEllA/CEllT Toulouse (September lOth, 1987) and ONEnA/Chalillon
(September 20th-:30th, 1988), the fourth European Drag Reduction WorLing Party
:'Ieeting \\'itS held at EPF Lausanne on July 2cHh, 1989 under the auspices of the
£11COFTAC Pilot Centre by invitation of Professor 1.1. 11yhming and Doctor T.V.
Truong. T\\'ellty six participants from fi \'e European count ries (Fra nce, CermallY,
S \\' i tzerl a nd, The N etherla nels and U ni ted Kingdom), together \\'il h collaborating
colleagues from Canada, presented 18 contributions of \\'ork which eilher had heen
recently completed or was in progress. The purpose of this Proceedings Book is
to pro\'ide papers '\'hich reflect the contents of the talks given at that conference.
n
It should lw lloled that "A report on the 4 th European Drag eduction \\'orking
Party T\lccting" \\"as published in the EHCOFTAC Bulletin IV. December 19S'}
011 a personal note, I would like to say how grateful I am to all the rc1'erees
for reviewing some of the dozen or so papers offered after the meeting. Thanks
to their assist ance. this Proceedings Book should be published in time for the :5th
\\'orking Parly i\Ieeting which will be held at I3i\IT Fluid i\Iechanics Limited. Ted
dington. Uniled Kingdom. I would also like to thank Doctor Nigel Hollillg\\'orth,
frolll KIll wer academic ))ll blishers, for all his va 1u able commen b dming the prepa
ration of this Proceedings Book.
Toulouse, August 1990
E. Coustols
vii
Final Programme
4th European Turbulent Drag Reduction
\\lorking Meeting 1989
S,viss Federal Institute of Technology
Lausanne EPFL - July 24th, 1989
Session 1 - External l\1anipulators in Internal and External Flows
(Chairman: E. Coustols)
High speed LEBU device drag measurements. J.P. Bonnet &; J. Delville
Complementary drag reduction measurements. L.C. Squire &; A.:'.I. Savill
I-Combination of riblets and manipulators at low Re ; 2-Some observations of tllC
static pressure distributions in pipe flow perturbed by a LEEU ring. Y.D. I\guyen
&; J. Dickinson
Turbulent pipe flow manipulation and modelling. A. Pollard, A.'\1. Sa,'ill &; H.
Thomann
Session :2 - Internal l\1anipulators : Riblets. (Chairman: A.::\I. Savill)
Effects of pressure gradients on riblets. K.S. Choi
Pressure grilc1icnts on riblcts in subsonic and transonic flm\"s. E. Coustols
Further supc'I".sonic riblet results. L. Gauclet (presented by A.:\f. Sa\'ill)
::\[ultiple light-plane flow visualisation of the structure \\"ithin riblcts. D. Clark
Rihlcts ill Cl difl"llser. Ph. Puh'in
Hiblets in a channel flow. ::\1.\1. Lm\'son
Flml" \'isllalisdtion ancl turbulence measurements moer micro-grooves. 1\:. Prasad c\.:
IT. Schwarz
Hiblds on a cylinder. D . .'\eumalln
Session j - Other Drag Reduction Approaches and l\lodelling.
(Chairman: 1.L. Hyhming)
Complltations of turbulent How in L-shaped riblets. R.E. Launder &; Li Shaopillg
Computations for L-shaped riblets in laminar boundary layers. E. Coustols
:r.
:further riblet computations in a laminar boundary layer. Anselmet ,\.: L. Djenicli
CurY<ltme cll'ag reduction modelling. A.flI. Savill S: T.B. GatsLi
Video flow \Oisualisation of sparse d-type "roughness" including effect of an aerol"oil
LEBU. P. Filllourakis & A.M. Savill
Sessioll /[ - Round Table. (E. Coustols, A.M. Savill &; LL. Ryhming)
ix
Balance of Turbulent Kinetic Energy
Downstream a Single Flat Plate Manipulator
Comparisons Between Detailed Experiments and
Modelling.
c. Tenaud - J. Lemayt - J.P. Bonnet - J. Delville
Centre d'Etudes Aerorodynamiques et Thenniques,
1. E. A. - U. R. A. C.N.R.S. 191
43, Route de l'Aerodrome, 86000 Poitiers, FRAT\CE.
t Present address: Mechanical Engineering Department,
Laval University, Quebec, CA:r\TADA G1K 7P4
Summary
Previous numerical studies undertaken at ONERA/CERT /DERAT in Toulouse, ha\'e
shO\vn that usual closures, using three or five equations, were able to quite well repro
duce the developpement of a manipulated boundary layer for the specific geometrical
configuration given from CERT. The goal sought after, in this study. is to check
the predictiw capabilities of the CERT code on an other specific configuration. given
from CEAT Poitiers, for which detailed experiments were available in the downstream
vicinity of an external manipulator of a rectangular section. In the .'\ avier-Stokes
equations, the unsteady and the diffusion terms in the streamwise direction are ne
glcctecl. For the turbulent motion, a two layer model is adopted using a mixing length
scheme in the near wall region and a k, E, u'v' transport equations model everywhere
else. A brief description of the numerical procedure is first given. The experimental
apparatus and techniques are then described. The numerical results agree qualita
tively \yell with the experimental mean velocity, turbulence and shear stress data
profiles. The experiments provide the terms of the energetic balance of the kinetic
energy equation ; they are, for further information, compared with the numerical
terms. Although the manipulated flow is strongly out of equilibrium, conventional
closure models appear to be able to predict rather correctly the measured quantities,
particularly the turbulent diffusion term and the dissipation behaviour.
2
1 Introduction
During the last decade, lot of experiments have been conducted in order to reduce skin
friction drag by the control of the eddy structures of turbulent boundary layers. For
airfim'>s, the techniques proposed can be divided into active and passive ones [2], [15].
One of the passive methods consists in immerging thin ribbons, having either rectan
gular or aerofoil section, within the external part of a turbulent boundary layer. This
method, so called external turbulence manipulation, is studied in this article.
Experimental investigations have shown that the mechamisms leading to drag re
duction are complex. Among several effects, one can notice that the externalmanipu
lator induces large skin friction reductions and spectacular modifications on turbulent
profiles (excess of turbulence level in the device wake. important decreases belm\' the
mean axis of this wake, ... ). Furthermore, the manipulated boundary layer is highly
out of equilibrium O\'er a large dmvnstream extent.
Besides these experiments, numerical studies have been undertaken. The goal
was then to check usual turbulent closures, using several transport equations, for spe
cific geometrical configurations. l"lost of the numerical codes, used up to now. '\Tre
based on boundary layer assumption and thereby started downstream of the device
with the initial data given from experiments. These numerical studies have been
reviewed by Coustols &: Savill [4]. Let us point out that, using appropriate initiali
sations. authors were able to represent the mean and fiuctuating velocity profiles at
further stations downstream of the manipulator with a satisfactory agreement with
experiments. However, if one aims, for instance, at optimizing the device geometry,
it is necessary to start the computation upstream of the device and to follow the
whole of the fiow development. This second approach has been used in works pre
viously undertaken at the Aerodynamic department of ONERA/CERT [3]. [13]. On
a given experimental configuration, check of several closure models have been done:
two, three and fiw transport equations, using cOlwentional turbulence models. The
conclusions ,'>as, though the k - E model was able to reproduce qualitati"ely the be
haviour of such manipulated flow, better results have been obtained using three or
five transport equations. The mean and turbulence velocity profiles as well as the
skin friction coefficient have been calculated in better agreement with the experimen
tal data [3] [13]. Let us point out that three or five equations models give rather
comparable results, except that the latter allows to get a better representation of the
C f evolution. A remaining question can be pointed out: Is these conclusions on the
CERT configuration stay valid for different device geometries?
The purpose of this study is then to check the predictive capabilities of the
C.E.R.T. numerical code on an other configuration given from the C.E.A.T. Poitiers,
for which detailed experiments were available in the downstream vicinity of an ex
ternal manipulator having rectangular section [9], [10]. We decided to restrict the
present numerical approach by using only the three transport equations code. This
option gives a good compromise between computer time saving, previous prediction
3
quality and detailed description of the turbulent field.
A brief description of the numerical procedure is first given ; the experimental
apparatus and techniques are described, then a comparison between experiments and
modelling on the mean and fluctuating profiles at further locations downstream of
the manipulator is discussed. The experiments provide the energetic balance of the
kinetic energy equation. Then, for further information, we compare the numerical
terms of the k transport equation with their experimental estimations.
2 Numerical approach.
2.1 Basic equations.
The equations of the mean flow are the Reynolds averaged Navier-Stokes equations.
The usual two-dimensional assumptions are used; x represents the streamwise direc
tion and y the axis normal to the wall. The unsteady terms as well as the diffusion
ones in the :r direction are neglected. It follows:
aU aV
-+-=0. (1)
a:r ay
a ([J[j) + a (UV) = _~ aP +.!!.- [~ (aU)] + .!!.- (-U'2) + .!!.- (-177l)
aol' ay pool' ay p ay ax ay (2)
a(0'V) + a(11V) _~ of +.!!.- [~(a1l)] +.!!.- (-u'v') +.!!.- (_v'2)
=
ax ay p ay ay p ay a:r ay (3)
For the turbulent motion, a two-layer model is adopted:
1. Although the flow is out of equilibrium even close to the ,Yall, a mixing length
scheme is applied, for simplicity, in the near wall regions (up to y+ = 60),
including the lower and upper sides of the device. This scheme is based upon
an eddy \'iscosity assumption:
(aU; aUj)
- -u,·u--, = -IPII -aXj + -ax-; - -32k fJ (4)
I ] IJ
The eddy viscosity coefficient {LI is expressed, using a mixing length formulation.
as follows:
(5)
where I is the mixing length and F the Van Driest type corrector function for
the viscous sublayer. The use of this scheme, close to the manipulator, can be
