UNIVERSITY OF BELGRADE FACULTY OF MECHANICAL ENGINEERING Taha A. Abdullah TWO ...

144 Pages·2014·3.56 MB·English

UNIVERSITY OF BELGRADE

FACULTY OF MECHANICAL ENGINEERING

Taha A. Abdullah

TWO-DIMENSIONAL WIND TUNNEL MEASUREMENT
CORRECTIONS BY THE SINGULARITY METHOD

Doctoral Dissertation

Belgrade, 2014
UNIVERZITET U BEOGRADU

MAŠINSKI FAKULTET

Taha A. Abdullah

ODREĐIVANJE KOREKCIJA U DVODIMENZIONALNIM
AEROTUNELSKIM MERENJIMA METODOM
SINGULARITETA

doktorska disertacija

Beograd, 2014
Dedicated to my parents, wife and daughters
EXAMINATION COMMITTEE

Advisor: Prof. Dr. Zlatko Petrovic
Full Professor
University of Belgrade, Faculty of Mechanical
Engineering

Co-Advisor: Prof. Dr. Ivan Kostic
Associate Professor
University of Belgrade, Faculty of Mechanical
Engineering

Members: Prof. Dr. Zoran Stefanović
Full Professor, retired
University of Belgrade, Faculty of Mechanical
Engineering

Date of defence
Komisija za ocenu i odbranu disertacije:

Mentor: Prof. dr. Zlatko Petrovic
redovni profesor
Mašinski fakultet Univerziteta u Beogradu

Komentor: Prof. dr. Ivan Kostic
vanredni profesor
Mašinski fakultet Univerziteta u Beogradu

Members: Prof. dr. Zoran Stefanović
redovni profesor u penziji
Mašinski fakultet Univerziteta u Beogradu

Datum odbrane:
ACKNOWLEDGEMENTS

I would like to express my sincere thanks and gratitude to my advisor professor
Zlatko Petrovic for his valuable and continuous advice, thoughtfulness and assistance
throughout the duration of this work.
I would like to express my sincere thanks and gratitude to my co-advisor
professor Ivan Kostic. This research would not have been accomplished without their
support and patience in every phase of this thesis from the initial to the final level and
enlightened the work with their vast knowledge on the subject.
I would also like to extend my sincere gratitude to Professor Zoran Stefanovic
for his contributions, guidance and advices.
I also would like to take this opportunity to thank my mother and my brothers
who are surely proud of me on this day.
Special thanks to the staffs, students and friends that I have met during my
research work especially those in the Mechanical Engineering Department.

Lastly but most importantly, I want to express my gratitude to my wife and my
lovely daughters each of whom gave me support, encouragement and love in my life
and made this thesis possible.

Above all, I am very much grateful to almighty Allah for giving me courage
and good health for completing the venture.

Mr. Taha Ahmed
TWO-DIMENSIONAL WIND TUNNEL MEASUREMENT
CORRECTIONS BY THE SINGULARITY METHOD
Abstract
The novel approach to two-dimensional wind tunnel measurement corrections for the
airfoils has been established and applied in this thesis. Flow about the airfoil is
simulated by approximating the actual airfoil shape by linearly varying vorticity
elements distributed along a finite number of panels, positioned along its contour
(panel method), both for free flow conditions, and for flow conditions in wind tunnel
test section. The difference in calculated pressure coefficient distributions about the
airfoil in free flow and in wind tunnel is either applied directly as a correction to the
measured pressure distributions, or after its integration, to the measured aerodynamic
lift and moment coefficients. Solid wind tunnel walls are simulated by repeated
mirroring of the paneled airfoil shape with respect to position of the test section walls.
Porous walls are simulated similarly as solid walls, while transpiration is simulated by
singularities of sources/sinks type, distributed along test section walls. Intensity of
sources/sinks is determined to closely approximate results of measurements in wind
tunnel with the calculated aerodynamic parameters (pressure distribution and/or
aerodynamic coefficients). Calculated wind tunnel parameters and corrections have
been compared, and have shown good agreements both with classical wind tunnel
corrections, and with experimental data obtained from two relevant wind tunnel
facilities.
Keywords: wind tunnel corrections, singularity method, solid and porous walls, wall
interference, pressure coefficient distribution.
Scientific field:
Technical Sciences, Mechanical Engineering
Narrow scientific field:
Aeronautical Engineering
UDC number:
I
ODREĐIVANJE KOREKCIJA U DVODIMENZIONALNIM
AEROTUNELSKIM MERENJIMA METODOM SINGULARITETA
Sažetak
U okviru ove disertacije formiran je i primenjen novi proračunski model, namenjen
korekcijama u dvodimenzionalnim aerotunelskom ispitivanjima. Strujanje oko
aeroprofila modelira se aproksimiranjem realnog oblika aeroprofila vrtložnihm
elemenatima linearno promenljivog intenziteta raspoređenih po konačnom broju panela
na njegovoj konturi (panel metod), kako za slučaj slobodnog strujanja, tako i za slučaj
strujanja u radnom delu aerotunela. Razlika u proračunskoj raspodeli koeficijenta
pritiska oko aeroprofila u slobodnoj struji i u aerotunelu primenjuje se ili kao
neposredna korekcija superponiranjem sa izmerenim vrednostima koeficijenta pritiska
u aerotunelu, ili nakon integraljenja kao korekcija izmerenim vrednostima
aerodinamičkih koeficijenata uzgona i momenta. Čvrsti zidovi aerotunela simulirani su
serijom paneliranih kontura konkretnog aeroprofila, preslikanih po principu likova u
ogledalu u odnosu na zidove radnog dela. Porozni zidovi simulirani su na isti način, pri
čemu se prostrujavanje kroz njih simulira singularitetima tipa izvor/ponor postavljenim
po zidovima radnog dela. Intenziteti izvora/ponora određuju se tako da sračinatim
aerodinamičkim parametrima adekvatno aproksimiraju rezultate merenja u aerotunelu
(raspodelama pritiska i/ili aerodinaičkim koeficijentima). Sračunati aerotunelski
parametri i korekcije upoređeni su, i pokazali su dobra poklapanja kako sa korekcijama
dobijenim klasičnim metodama, tako i sa rezultatima merenja obavljenim u dve
renomirane institucije u oblasti eksperimentalne aerodinamike.
Ključne reči: aerotunelske korekcije, metod singulariteta, čvrsti i porozni zidovi,
uticaj zidova, raspodela koeficijenta pritiska.
Naučna oblast:
Tehničke nauke, Mašinstvo,
Uža naučna oblast:
Vazduhoplovstvo
UDK broj:
II
Table of Contents
TWO-DIMENSIONAL WIND TUNNEL MEASUREMENT CORRECTIONS BY
THE SINGULARITY METHOD ........................................................................................... I
Abstract I
CHAPTER ONE ..................................................................................................................... 1
1 INTRODUCTION ................................................................................................... 1
1.1 Background .............................................................................................................. 1
1.2 Literature review ...................................................................................................... 3
1.3 Wall interference corrections from boundary measurements .................................. 9
1.3.1 Early blockage corrections for solid walls ............................................................... 9
1.3.2 Method of Capelier, Chevauier and Bouniol ......................................................... 10
1.3.3 Method of Mokry and Ohman ............................................................................... 11
1.3.4 Method of Paquet ................................................................................................... 12
1.3.5 Method of Ashill and Weeks ................................................................................. 12
1.3.6 Methods of Kemp and Murman ............................................................................. 13
CHAPTER TWO .................................................................................................................. 14
2 THE METHOD OF SINGULARITIES AND ITS APPLICATION IN
SIMULATION OF FLOW IN WIND TUNNEL TEST SECTIONS .................................. 14
2.1 Two-dimensional point singularity elements ......................................................... 14
2.1.1 Two-dimensional point source ............................................................................... 14
2.1.2 Two-Dimensional Point Doublet ........................................................................... 15
2.1.3 Two-Dimensional Point Vortex ............................................................................. 15
2.2 Two-dimensional constant-strength singularity elements ..................................... 16
2.2.1 Constant-strength source distribution .................................................................... 17
2.2.2 Constant-Strength Doublet Distribution ................................................................ 20
2.2.3 Constant-strength vortex distribution .................................................................... 22
2.3 Two-dimensional linear-strength singularity elements .......................................... 24
III
2.3.1 Linear Source Distribution ..................................................................................... 25
2.3.2 Linear doublet distribution ..................................................................................... 27
CHAPTER THREE .............................................................................................................. 31
3 CLASSICAL WIND TUNNEL CORRECTIONS FOR TEST SECTIONS
WITH SOLID WALLS ........................................................................................................ 31
3.1 Classical wall corrections assumption ................................................................... 31
3.1.1 Coordinate System and Governing Equations ....................................................... 32
3.1.2 Model Representation ............................................................................................ 34
3.1.3 Tunnel Wall ........................................................................................................... 35
3.2 Application of the correction method .................................................................... 37
3.2.1 Classical correction for Lift Interference ............................................................... 38
3.2.1.1 2D Lift interference ............................................................................................ 38
3.3 Classical correction for blockage interference ....................................................... 41
3.3.1 2D solid blockage for small models ...................................................................... 41
3.4 Wake blockage ....................................................................................................... 44
CHAPTER FOUR ................................................................................................................ 46
4 CLASSICAL CORRECTIONS FOR VENTILATED TEST SECTIONS ........... 46
4.1 Background, assumptions, and definitions ............................................................ 49
4.2 Wall boundary conditions ...................................................................................... 53
4.2.1 Ideal ventilated wall boundary conditions ............................................................. 55
4.3 Interference in 2d testing ....................................................................................... 57
4.3.1 Interference of small models, uniform walls ......................................................... 57
CHAPTER FIVE .................................................................................................................. 62
5 NEW APPROACH IN NUMERICAL MODELING OF WIND TUNNEL
CORRECTIONS .................................................................................................................. 62
5.1 Motivation for the 2D wind tunnel wall corrections .............................................. 62
IV