Scale Effects on Aircraft and Weapon Aerodynamics

249 Pages·2003·15.86 MB·English

iAGARD-AG-323
CO
CM
CO
6
<
a
ADVISORY GROUP FOR AEROSPACE RESEARCH & DEVELOPMENT
<
7RUEANCELLE 92200 NEUILLYSUR SEINE FRANCE
<
uJ I Mir
-■■-: T. ■■■<?■« j»^,,, f..j--™ QVW jpj
«:i ftWtf 'Aewt \aifc J.
F s * MAR 1] 5119951$
i«r.-- >-.■-) ' til!
AGARDograph 323
Scale Effects on
Aircraft and Weapon Aerodynamics
(Les Effets d'Echelle et l'Aerodynamique
des Aeronefs et des Systemes d'Armes) 35
This AGARDograph has been produced at the request of the
Fluid Dynamics Panel ofAGARD.
19950314 134
„. .^w#!l*s*i'
- NORTH ATLANTIC TREATY ORGANIZATION
Published July 1994
Distribution and Availability on Back Cover
AGARD-AG-323
ADVISORY GROUP FOR AEROSPACE RESEARCH & DEVELOPMENT
7RUEANCELLE 92200 NEUILLYSUR SEINE FRANCE
AGARDograph 323
Scale Effects on
Aircraft and Weapon Aerodynamics
(Les Effets d'Echelle et l'Aerodynamique
des Aeronefs et des Systemes d'Armes)
by Edited by
A.B. Haines Professor A.D. Young
3 Bromham Road 70 Gilbert Road
Biddenham Cambridge C84 3PD
Bedford MK40 4AF United Kingdom
United Kingdom
This AGARDograph has been produced at the request of the
Fluid Dynamics Panel of AGARD.
North Atlantic Treaty Organization
Organisation du Traite de l'Atlantique Nord
The Mission of AG ARD
According to its Charter, the mission of AGARD is to bring together the leading personalities of the NATO nations in the fields
of science and technology relating to aerospace for the following purposes:
- Recommending effective ways for the member nations to use their research and development capabilities for the
common benefit of the NATO community;
- Providing scientific and technical advice and assistance to the Military Committee in the field of aerospace research and
development (with particular regard to its military application);
- Continuously stimulating advances in the aerospace sciences relevant to strengthening the common defence posture;
- Improving the co-operation among member nations in aerospace research and development;
- Exchange of scientific and technical information;
- Providing assistance to member nations for the purpose of increasing their scientific and technical potential;
- Rendering scientific and technical assistance, as requested, to other NATO bodies and to member nations in connection
with research and development problems in the aerospace field.
The highest authority within AGARD is the National Delegates Board consisting of officially appointed senior representatives
from each member nation. The mission of AGARD is carried out through the Panels which are composed of experts appointed
by the National Delegates, the Consultant and Exchange Programme and the Aerospace Applications Studies Programme. The
results of AGARD work are reported to the member nations and the NATO Authorities through the AGARD series of
publications of which this is one.
Participation in AGARD activities is by invitation only and is normally limited to citizens of the NATO nations.
The content of this publication has been reproduced
directly from material supplied by AGARD or the authors.
Published July 1994
Copyright © AGARD 1994
All Rights Reserved
ISBN 92-835-0754-1
Printed by Specialised Printing Services Limited
40 Chigwell Lane, Loughton, Essex IG10 3TZ
Recent Publications of
the Fluid Dynamics Panel
AGARDOGRAPHS (AG)
Design and Testing of High-Performance Parachutes
AGARD AG-319, November 1991
Experimental Techniques in the Field of Low Density Aerodynamics
AGARD AG-318 (E), April 1991
Techniques Experimentales Liees ä l'Aerodynamique ä Basse Densite
AGARD AG-318 (FR), April 1990
A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers
AGARD AG-315, May 1989
Reynolds Number Effects in Transonic Flows
AGARD AG-303, December 1988
REPORTS (R)
Missile Aerodynamics
AGARD R-804, Special Course Notes, June 1994
Progress in Transition Modelling
AGARD R-793, Special Course Notes, April 1994
Shock-Wave/Boundary-Layer Interactions in Supersonic and Hypersonic Flows
AGARD R-792, Special Course Notes, August 1993
Unstructured Grid Methods for Advection Dominated Flows
AGARD R-787, Special Course Notes, May 1992
Skin Friction Drag Reduction
AGARD R-786, Special Course Notes, March 1992
ADVISORY REPORTS (AR)
Quality Assessment for Wind Tunnel Testing
AGARD AR-304, Report of WG15, July 1994
Air Intakes for High Speed Vehicles
AGARD AR-270, Report of WG13, September 1991
Appraisal of the Suitability of Turbulence Models in Flow Calculations
AGARD AR-291, Technical Status Reveiw, July 1991
Rotary-Balance Testing for Aircraft Dynamics z
o.ea
AGARD AR-265, Report of WG11, December 1990
S'SIS GM&J Of
Calculation of 3D Separated Turbulent Flows in Boundary Layer Limit
AGARD AR-255, Report of WG10, May 1990
Jnstif'leation
CONFERENCE PROCEEDINGS (CP)
Computational and Experimental Assessment of Jets in Cross Flow By.—. . _^_
AGARD CP-534, November 1993
High-Lift System Aerodynamics
AyaO.aM3.lfry „CaöPS
AGARD CP-515, September 1993
Theoretical and Experimental Methods in Hypersonic Flows
AGARD CP-514, April 1993
Aerodynamic Engine/Airframe Integration for High Performance Aircraft and Missiles
AGARD CP-498, September 1992
Effects of Adverse Weather on Aerodynamics
AGARD CP-496, December 1991
Manoeuvring Aerodynamics
AGARD CP-497, November 1991
Vortex Flow Aerodynamics
AGARD CP-494, July 1991
Missile Aerodynamics
AGARD CP-493, October 1990
Aerodynamics of Combat Aircraft Controls and of Ground Effects
AGARD CP-465, April 1990
Computational Methods for Aerodynamic Design (Inverse) and Optimization
AGARD CP-463, March 1990
Applications of Mesh Generation to Complex 3-D Configurations
AGARD CP-464, March 1990
Fluid Dynamics of Three-Dimensional Turbulent Shear Flows and Transition
AGARD CP-438, April 1989
Validation of Computational Fluid Dynamics
AGARD CP-437, December 1988
Aerodynamic Data Accuracy and Quality: Requirements and Capabilities in Wind Tunnel Testing
AGARD CP-429, July 1988
Aerodynamics of Hypersonic Lifting Vehicles
AGARD CP-428, November 1987
Aerodynamic and Related Hydrodynamic Studies Using Water Facilities
AGARD CP-413, June 1987
Applications of Computational Fluid Dynamics in Aeronautics
AGARD CP-412, November 1986
Store Airframe Aerodynamics
AGARD CP-389, August 1986
Unsteady Aerodynamics — Fundamentals and Applications to Aircraft Dynamics
AGARD CP-386, November 1985
Aerodynamics and Acoustics of Propellers
AGARD CP-366, February 1985
Improvement of Aerodynamic Performance through Boundary Layer Control and High Lift Systems
AGARD CP-365, August 1984
Wind Tunnels and Testing Techniques
AGARD CP-348, February 1984
Aerodynamics of Vortical Type Flows in Three Dimensions
AGARD CP-342, July 1983
Missile Aerodynamics
AGARD CP-336, February 1983
Prediction of Aerodynamic Loads on Rotorcraft
AGARD CP-334, September 1982
Wall Interference in Wind Tunnels
AGARD CP-335, September 1982
Fluid Dynamics of Jets with Applications to V/STOL
AGARD CP-308, January 1982
Aerodynamics of Power Plant Installation
AGARD CP-301, September 1981
I
Preface
The primary aims of this AGARDograph are:
(i) to review the present state of knowledge on scale effects at high lift and low speeds,
(ii) to update the reviews in AG-303 and AR-224 of scale effects in transonic flow and in particular, to comment on the
achievements and limitations of the methodology proposed in AR-224 for testing in transonic tunnels and extrapolating
results to full-scale,
(iii) to review knowledge on scale effect on topics such as afterbody drag, flow over forebodies at high incidence, unsteady
flow in open cavities, intakes, propellers and the effects of ice accretion,
(iv) to draw attention to the large number of pseudo-Reynolds-number effects that can confuse the derivation of true genuine
Reynolds-number effects.
Most space is given to objective (i). This is only to be expected: high lift at low speeds is fertile ground for genuine scale effects
and yet, surprisingly, it has not been the subject of any previous AGARDograph. In the present document, the subject is
considered logically, moving progressively from scale effect on single-element aerofoils to multiple aerofoils with deployed
high-lift devices and then to three-dimensional wings including swept and slender wings and then, finally, to complete aircraft
with all their practical complications.
Indeed, a deliberate feature of the AGARDograph is that in all areas, the emphasis is ultimately on the scale effect that has been
observed in flight-tunnel comparisons for actual specific aircraft. It is clear that advances in aircraft design have led to the need
for model tests to be undertaken at higher Reynolds numbers for the results to be extrapolated with confidence to full-scale. It is
no longer true that a Reynolds number of say, Re = 6 x 106 is adequate either at low speeds or at transonic speeds. The data also
demonstrate that scale effects at relatively high Reynolds numbers are not necessarily favourable; significant adverse effects
have been observed and those are explained in principle in the AGARDograph.
Much has been learned about the reasons for scale effect but precise prediction can still be difficult and the report ends with a set
of 20 recommendations for further research. The need for improved predictions of transition, for regular observations of
transition in routine testing and for the application of CFD codes at both model and full-scale Reynolds numbers is emphasised.
This AGARDograph has been prepared at the invitation of the Fluid Dynamics Panel of AGARD.
Preface
Les principaux objectifs de cette AGARDographie sont les suivants:
(i) faire le point de l'etat de Fart des effets d'echelle en hypersustentation ä basse vitesse.
(ii) mettre ä jour les communications publiees dans AG-303 et AR-224, sur les effets d'echelle en ecoulement transsonique,
et, en particulier, de commenter les realisations et les limitations de la methodologie proposee dans AR-224 pour les
essais en soufflerie transsonique et 1'extrapolation des resultats en grandeur reelle.
(iii) revoir l'etat des connaissances en ce qui concerne les effets d'echelle sur la trainee d'arriere corps, l'ecoulement ä forte
incidence autour des ogives, les ecoulements instationnaires en cavite ouverte, les entrees d'air, et les effets de
l'accumulation de glace.
(iv) attirer 1'attention sur les nombreux effets des pseudo-nombres de Reynolds qui peuvent creer la confusion quant ä la
derivation des effets des vrais nombres de Reynolds.
La majeure partie de l'ouvrage est consacree ä l'objectif defini ci-dessus (i). Ceci n'est guere surprenant car le sujet de
l'hypersustentation ä basse vitesse represente un terrain fertile pour les effets d'echelle authentiques. II est pourtant surprenant de
constater qu'il n'a jamais fait l'objet d'une AGARDographie. Dans le present document, le sujet est traite de facon logique, en
commencant par l'effet d'echelle sur des profils ä element simple, pour examiner ensuite les profils multiples avec
hypersustentateurs deployes, les voilures tridimensionnelles, y compris les ailes en fleche et les ailes minces, et enfin l'aeronef
complet avec toutes les complications d'ordre pratique concomitantes.
A dire vrai, cette AGARDographie met deliberemment l'accent sur les effets d'echelle observes lors des comparaisons faites
entre differents appareils en soufflerie. II est clair que suite aux progres realises au niveau de la conception des aeronefs il est
desormais necessaire d'effectuer les essais sur maquette ä des nombres de Reynolds plus eleves, pour que les resultats puissent
etre extrapoles en grandeur reelle en toute confiance. Dire qu'un nombre de Reynolds de Re = 6 x 106 par exemple, est adequat ä
basse vitesse ou ä vitesse transsonique, n'est plus possible. Les donnees recueillies indiquent egalement que les effets d'echelle
aux nombres de Reynolds relativement eleves ne sont pas necessairement favorables; des effets inverses appreciables ont ete
notes et le principe de ceux-ci est explique dans cette AGARDographie.
Beaucoup d'enseignements ont ete tires au sujet des causes des effets d'echelle mais les predire avec certitude reste delicat.
Ainsi, le rapport conclut par une serie de 20 recommandations pour des futurs travaux de recherche. L'accent est mis sur la
necessite de ameliorer la prevision de la transition, la realisation d'observations regulieres de la transition lors des essais courants
et l'application des codes CFD aux nombres de Reynolds maquette et grandeur reelle.
Cette AGARDographie a ete realisee ä la demande du Panel AGARD de la dynamique des fluides.
Contents
Page
Recent Publications of the Fluid Dynamics Panel iii
Preface v
Preface vi
1 Introduction 1
2 Scale, Reynolds Number and Pseudo-Reynolds Number Effects 1
2.1 Scale Effects (not to be classed as Reynolds Number Effects) 2
2.1.1 Model geometric fidelity 2
2.1.2 Aeroelastic effects 3
2.2 Pseudo-Reynolds Number Effects 3
2.2.1 Type I effects 4
2.2.1.1 Tunnel calibration 4
2.2.1.2 Wall interference 4
2.2.2 Type II effects 6
2.2.2.1 Noise and stream turbulence 6
2.2.2.2 Transition position and length 7
2.2.2.3 Tunnel temperature 8
2.2.2.4 Rotational speed in propeller testing 9
2.2.3 Type III effects 9
2.2.3.1 Humidity 9
2.2.3.2 Thermal non-equilibrium 9
2.2.3.3 Model manufacturing accuracy 10
2.2.3.4 Model surface finish 10
2.2.3.5 Model support/mounting effects 10
2.2.3.6 Inclination of thrust vector 11
2.2.3.7 Final remarks 11
3 Scale Effects at High Lift and Low Speeds 27
3.1 Two-Dimensional Single Aerofoils 27
3.1.1 Sources of data 27
3.1.2 Types of stall 27
3.1.3 Sources of scale effect and their prediction 28
3.1.3.1 Bubble growth and bursting 28
3.1.3.2 Leading-edge stall by turbulent re-separation 30
3.1.3.3 Turbulent separation ahead of the trailing edge 31
3.1.4 Examples of scale effect 32
3.1.4.1 Early NACA tests 32
3.1.4.2 Other examples 33
3.1.4.3 Summary of conclusions 35
3.2 Two-Dimensional Multi-Element Aerofoils 35
3.2.1 Sources of scale effect 35
3.2.2 Examples of scale effect 37
3.2.2.1 Flap effectiveness 37
3.2.2.2 Slat effectiveness 40
3.2.2.3 Scale effect for complete configuration 40
Page
3.2.3 Theoretical prediction of scale effects 42
3.2.4 Summary of conclusions 43
3.3 Three-Dimensional Wings 44
3.3.1 Sources of scale effect 44
3.3.2 Transition prediction for a sweptback wing 45
3.3.2.1 Transition due to cross-flow instability 45
3.3.2.2 Transition due to contamination along the attachment line 46
3.3.3 Examples of scale effect on wings of low sweepback 47
3.3.3.1 Conventional scale effect 47
3.3.3.2 Bubble-dominated scale effect 48
3.3.3.3 Slot-flow dominated scale effect 48
3.3.3.4 Transition-dominated scale effect 49
3.3.4 Examples of scale effect on wings of moderate sweepback 50
3.3.4.1 Early evidence: conventional and bubble-dominated 50
scale effect
3.3.4.2 Recent evidence: transition-dominated scale effect 52
3.3.5 Examples of scale effect on slender wings 53
3.3.5.1 Sources of data 53
3.3.5.2 Slender wings with sharp leading edges 53
3.3.5.3 Slender wings with round leading edges 54
3.3.5.4 Updated interpretation of earlier results and conclusions 56
3.4 Complete Aircraft 57
3.4.1 Introduction 57
3.4.2 The overall picture 58
3.4.2.1 C : evidence from model tests 58
Lmax
3.4.2.2 C : flight-tunnel comparisons 59
Lmax
3.4.2.3 Post-stall pitching moments 60
3.4.3 Examples of scale effect for specific aircraft 60
3.4.3.1 UK aircraft 1945-1965 60
3.4.3.2 Boeing 747 61
3.4.3.3 The Fokker family 62
3.4.3.4 The Airbus family 63
3.4.4 3D problem areas 63
3.4.5 Summary of general conclusions 65
Scale Effects at Transonic Speeds 139
4.1 Introduction 139
4.2 Recapitulation of AGARD Methodology 139
4.3 Recent Research (including Experience with Methodology) 140
4.3.1 Effects of a rear separation 140
4.3.2 Conversion of aft transition to Re with forward transition 141
EFF
4.3.3 Examples of scale effect 142
4.3.3.1 Wave drag 142
4.3.3.2 Shock-induced separation 143
4.3.3.3 Buffet-onset 144
4.4 Limitations on Ability to Apply Methodology 144
4.5 Research Not Directly Connected with Methodology 145
4.5.1 Unsteady flow in buffet 145
4.5.2 Combat aircraft wings 146
4.5.3 Slender wings 147
4.6 Conclusions and Possible Future Trends 147
Page
5 Scale Effects on Aircraft Drag 166
5.1 Prediction of Wave Drag and Viscous Drag 166
5.2 Flight-Tunnel Comparisons 167
5.3 Afterbody Drag 168
5.3.1 Genuine or pseudo re-effect? 168
5.3.2 Evidence from research tests 169
5.3.3 Evidence from tests for specific aircraft 170
5.3.4 Conclusions 171
6 Scale Effects in Flow over Bodies 180
6.1 Transition and Types of Flow 180
6.2 Body Forces and Moments at High Incidence and Zero Yaw 182
6.3 Forebody Flow on the F/A 18 185
6.3.1 Surface flow patterns 185
7 Scale Effects in other Important Areas 204
7.1 Internal Store Carriage 204
7.2 Intakes 205
7.3 Propellers 206
7.4 Ice Accretion 208
8 Conclusions and Recommendations 222
9 Acknowledgements 225
References 226