a computational simulation of rotor...

A COMPUTATIONAL SIMULATION OF ROTOR-FUSELAGE FLOW

INTERACTION IN HOVERING AND FORWARD FLIGHT

MOHAMAD HAFIZ BIN ISMAIL

A thesis submitted in fulfilment ofthe

requirements for the award of the degree of

Master ofEngineering (Mechanical)

Faculty ofMechanical Engineering

Universiti Teknologi Malaysia

JULy 2007

v

ACKNOWLEDGEMENT

Before proceeding any further, I would very much like to take this moment

bestowed upon all to utter my utmost gratitude and love to each person involved in

this research for their have given undying support through out the completion of my

study.

Thank you to my supervisor; Prof. Ir. Dr. Hj. Abas Bin Ab. Wahab for his

patience and concern in aiding me through these years. His ever willingness and

kindness for guiding me as well as providing me with valuable information are truly

appreciated. You came into my life and pelt your unstoppable useful advices in my

life and giving me strength in every each day to have hopes again.

Gratitude to my gracious colleagues; Nik, Syafiq and Sukri who had been

with me through all my trials and tribulations for all these years. I can never forget

the greatest encouragement of my beloved friend that bring me joy in my life here;

Zalmy, Azril, Firdaus, and Kamil; given for me in every walk of life and their

moral and undivided support. The memories that we had with all of you will be

treasured forever. Not to forget to Siti, who always there during for final touch-up.

Hope to see you at the top.

I gather all my sincerest gratitude to offer my gracious and benevolent thank

you to my loving family, especially my father, who extremely being my source of

strength throughout these years. Thank you for believing in me.

Last but the foremost, I thank Allah The Almighty for giving me the

opportunity and the courage in completing everything needed to be done to see this

thesis bind.

Thank you and may Allah bless all of you.

vi

ABSTRACT

A helicopter rotor-fuselage flow interaction has been studied theoretically and

numerically. The study began with the analysis of the induced velocity by helicopter

rotor both in hovering and forward flight by using Momentum Theory, Blade

Element Theory and Blade Element Momentum Theory. Three-dimensional steady

and unsteady simulations of rotor-fuselage flow interaction have been conducted

using Computational Fluid Dynamics (CFD) commercial software FLUENT 6.2 on

ROBIN and AS355 helicopter. The study on ROBIN is to justify the method used in

CFD simulation for this current research on AS355 is correct. The study emphasizes

on flow generated during hovering and forward flight onto the helicopter fuselage.

Aerodynamic forces on the fuselage have been obtained through theoretical analysis

and numerical simulation. The Spalart-Allmaras turbulent model has been utilized to

model the physics of flow related to the helicopter fuselage. This model is chosen in

terms of its reliability, practical and proven to be effective in modeling the rotor-

fuselage flow interaction. The simulation was first carried out in steady state using

Moving Reference Frame capability in FLUENT 6.2. this is then followed by

unsteady simulation using Sliding Mesh Model, which is a time accurate simulation.

Unsteady simulation was carried out because the nature of rotor-fuselage flow

characteristic that is unsteady and periodic with time along azimuth angle. From this

research it is found that the flow on the helicopter fuselage can be divided into two

parts, which is a complex unsteady aerodynamic interaction that occur during

hovering and low advance ratio, and a steady aerodynamic condition that occur at

high advance ratio. At high advance ratio the rotor wakes flows above the body and

only interacts with the fuselage pylon, and at this point the flow field of the

helicopter fuselage is dominated by free stream velocity. A fully three dimensional

and an unsteady computational method using Sliding Mesh Model has successfully

model the rotor-fuselage flow interaction in AS355, a 5-seater helicopter. These

results however provide preliminary understanding for designing the fuselage for

optimal aerodynamic characteristics.

vii

ABSTRAK

Interaksi aliran udara melalui bilah rotor dan fiuslaj helikopter dikaji secara

teori dan secara kaedah berangka. Kajian ini dimulakan dengan analisis halaju

teraruh daripada bilah rotor utama dalam keadaan apungan pugak dan penerbangan

kehadapan dengan menggunakan Teori Momentum, Teori Elemen Bilah dan Teori

Momentum Elemen Bilah. Simulasi tiga-dimensi dalam keadaan mantap dan tidak

mantap untuk aliran bilah rotor-fiuslaj dijalankan menggunakan perisian Dinamik

Aliran Berkomputer (CFD), FLUENT 6.2 terhadap helikopter ROBIN dan AS355.

Simulasi terhadap ROBIN dijalankan untuk mengesahkan teknik yang digunakan

terhadap AS355 adalah betul. Kajian meliputi aliran udara yang dihasilkan semasa

apungan pugak dan penerbangan kehadapan serta kesan aliran tersebut ke atas fiuslaj

helikopter. Daya-daya aerodinamik ke atas fiuslaj helicopter ditentukan secara teori

dan simulasi berangka. Persamaan gelora Spalart-Allmaras digunakan untuk

permodelan aliran di sekitar helicopter fiuslaj. Persamaan ini digunakan kerana

terbukti keberkesanannya dalam memodelkan interaksi aliran bilah-fiuslaj. Pada

mulanya, simulasi dijalankan dalam keadaan mantap menggunakan kaedah Kerangka

Rujukan Bergerak dalam FLUENT 6.2. Kemudian, diikuti dengan Model Gelincir

untuk keadaan tidak mantap, di mana kaedah ini adalah model yang sesuai bagi

masalah simulasi masa tepat. Simulasi keadaan tidak mantap dijalankan kerana

keadaan sebenar aliran bilah rotor-fiuslaj sendiri yang bergantung dengan masa dan

berkala bagi setiap pusingan bilah. Daripada kajian ini, didapati bahawa aliran udara

terhadap helikopter fiuslaj boleh dibahagikan kepada dua bahagian, iaitu interaksi

aerodinamik yang kompleks pada nisbah kehadapan rendah dan keadaan yang

mantap pada kelajuan nisbah kehadapan yang tinggi. Pada nisbah kehadapan yang

tinggi, aliran daripada bilah adalah tidak menyentuh fiuslaj dan hanya berinteraksi

dengan pylon sahaja dan pada keadaan ini, aliran udara adalah dipengaruhi oleh

aliran udara bebas. Kajian ini juga menunjukkan bahawa kaedah tidak mantap Model

Gelincir dapat memodelkan interaksi aliran bilah rotor-fiuslaj secara 3 dimensi pada

AS355, iaitu helicopter 5 penumpang dengan jayanya. Hasil kajian ini dapat

digunakan sebagai panduan awal untuk merekabentuk fiuslaj dalam keadaan yang

optimum dari segi ciri-ciri aerodinamik.

viii

TABLES OF CONTENTS

CHAPTER TITLE PAGE

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENT viii

LIST OF FIGURES xi

LIST OF TABLES xvii

NOMENCLATURE xviii

1 INTRODUCTION

1.0 Background 1

1.1 Problem Statement 2

1.2 Research Objectives 4

1.3 Research Scopes 4

1.4 Research Methodology 5

1.5 Thesis Outline 5

2 LITERATURE REVIEW

2.0 Introduction 6

2.1 Experimental Investigations 6

2.2 Singularity Method 14

2.3 Navier-Stokes Method 18

2.4 Hybrid Method 23

2.5 Present Approach 25

ix

3 THEORETICAL APPROACH TO HELICOPTER

AERODYNAMICS

3.0 Introduction 27

3.1 Induced Velocity in Hovering – a BEMT approach 27

3.1.1 The Governing Equations of BEMT 28

3.1.2 A Solution of BEMT Equations 29

3.2 Vertical Drag in Hovering 32

3.3 Induced Velocity in Forward Flight 34

3.3.1 Momentum Theory Analysis for α angleTPP 34

3.3.2 Momentum Theory Analysis for Inflow Equation 35

3.3.3 Mangler & Squire Model 37

3.4 Fuselages Lift and Drag in Forward Flight 40

4 COMPUTATIONAL FLUID DYNAMICS SIMULATION

4.0 Introduction 42

4.1 History of CFD 42

4.2 Fluent as a CFD Application 43

4.2.1 Pre-processing 44

4.2.2 Solving 44

4.2.3 Post-processing 44

4.3 The Governing Equations of CFD 45

4.3.1 Continuity Equations 46

4.3.2 Momentum Equations 48

4.4 The Navier-Stokes Equation in Rotating Frame of Reference 52

4.5 The Turbulence Model Assessment 54

4.6 The Spalart-Allmaras Turbulence Model 55

4.6.1 The Transport Equation 55

4.6.2 Modeling the Turbulent Viscosity 56

4.6.3 Modeling the Turbulent Production 56

4.6.4 Modeling the Turbulent Destruction 58

4.7 Discretization of the Governing Equation - the Finite Volume

Method

58

4.8 Mesh Generation and Wall Function Approach 59

x

4.9 Boundary conditions 60

4.9.1 Wall Boundary Condition 61

4.9.2 Inlet Boundary Condition 62

4.9.3 The Constant Pressure Boundary Condition 63

4.9.4 Interface between Grid Blocks-Sliding Mesh Theories 64

4.8 Convergence To Steady State 66

5 CFD MODELING OF HELICOPTER MODELS

5.0 Introduction 68

5.1 Models Preparation 68

5.1.1 NASA Langley ROBIN Model 69

5.1.2 AS355 Fuselage 72

5.1.3 ONERA 209 and NACA 0012 blades 73

5.2 Meshing and Boundary Condition 74

5.2.1 Mesh Type, Mesh Quality and Mesh Density 74

5.2.2 Mesh Assessment 76

5.2.3 Boundary Condition Definition 77

5.3 Solutions in Fluent 79

5.3.1 Discretization Scheme Assessment 80

6 RESULTS AND DISCUSSIONS

6.0 Introduction 83

6.1 ROBIN Results: Validation of Method used in CFD

Simulation

83

6.2 AS355 results: Rotor/Fuselage in Hovering 92

6.3 AS355 Results: Rotor/Fuselage in Forward Flight 97

7 CONCLUSIONS AND RECOMMENDATION

7.0 Introduction 120

7.1 Conclusions on the current work 120

7.2 Recommendations for future study 122

REFERENCES 123

APPENDIX

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Flow structure and some aerodynamic problem areas on a

helicopter in forward flight

3

2.1 Installation of the medium weight utility helicopter in the

Ames 40 by 80 foot wind tunnel

7

2.2 Sketch of basic faired body of the HU2K helicopter 8

2.3 ROBIN as a fuselage body with axes and signs

conventions

10

2.4 LV positioned in test chamber 11

2.5 The 2-meter rotor system in wind tunnel with lights on.

Longitudinal laser light sheet at Y/R = -0.8; µ = 0.15

12

2.6 Langley 14 by 22 foot subsonic tunnel 13

2.7 Rotor test stand and 3D LDV apparatus 14

2.8 Calculated X and Z components of total velocity on left

side of fuselage for µ=0.05 and CT=0.0050

15

2.9 Helicopter fuselage and tip vortex at µ=0.05 16

2.10 Surface streamlines α=50; Re = 4.46 x106; M = 0:062 17

2.11 Streamlines Released From the Disk Centerline 18

2.12 Apache streamlines at α=00 19

2.13 FLU3M computation using Navier-Stokes equation for

μ=0.05 and CT=0.00659 for ROBIN model

20

2.14 Structured and unstructured grid system for both FLOWer

and TAU respectively

21

2.15 ROBIN rotor wake visualization with overset rotor blades 22

xii

2.16 Velocity magnitude at forward flight mode of V = 40 m/s 23

2.17 Grid system used in the simulation 24

3.1 Annulus of rotor disc as used for a local momentum

analysis of the hovering rotor (a) plan view, (a) side view

29

3.2 A solution of BEMT using Microsoft excel 30

3.3 BEMT predictions of spanwise distributions of inflow and

thrust on a rotor blade for different twist. Results are

compared at a constant total thrust for (a) inflow ratio and

(b) thrust per unit span

31

3.4 Aircraft Element Used In Vertical Drag Analysis 33

3.5 (a) Distribution of dynamic pressure in wake and (b) drag

coefficient of typical component shapes

33

3.6 Forces acting on Helicopter in Forward Flight 35

3.7 The Inflow Ratio λ/λ as a function of forward speed ratio

µ/λ for several values of αh

h tpp

36

3.8 Variation in the longitudinal and lateral inflow across the

rotor disk according to the theory of Mangler & Squire (a)

longitudinal inflow for Type 1 and Type 3 loading (b)

lateral inflow for Type 1 and Type 3 loading

39

3.9 A Solution of Mangler & Squire model 40

3.10 (a) Example helicopter and (b) lift and drag characteristics

of the fuselage of the example helicopter

41

4.1 Road map of the governing equations in CFD 45

4.2 Finite control volume approach 46

4.3 Infinitesimal element approach 47

4.4 Infinitesimally small and moving fluid element 48

4.5 Illustration of (a) Shear Stress and (b) Normal Stress 49

4.6 Absolute and rotating frame of reference 52

4.7 Control volume of (a) cell centered scheme and

(b) cell vertex scheme

59

4.8 u Velocity cell at a wall boundary 62

4.9 u Velocity cell at the inlet boundary 63

4.10 P’-cells at an (a) Inlet Boundary and (b) Outlet Boundary 64

xiii

4.11 Zones Created by Interface Intersection 65

4.12 Two-Dimensional Grid Interface 66

4.13 Overview of the Segregated Solution Method 67

5.1 (a) Dimensions and 3-view drawing of NASA Langley

ROBIN model (b) 3 view drawing of NASA Langley

ROBIN model in SolidWorks

71

5.2 (a) Dimensions and 3 views drawing of AS355 (b) 3 views

drawing of AS355 fuselage in SolidWorks

72

5.3 (a) ONERA209 airfoil; (b) NACA0012 airfoil 73

5.4 Unstructured mesh on (a) the fuselage and main rotor blade

surface (b) outside the fuselage

75

5.5 Induced velocity versus blade radius for mesh assessment 77

5.6 Boundary conditions – blue: pressure inlet; red: pressure

outlet; yellow: wall (fuselage, blades and box); black:

interface

78

5.7 Boundary conditions – blue: velocity inlet; red: pressure

outlet; yellow: wall (fuselage, blades and box); black:

interface

79

5.8 Solver setting for steady simulation 80

5.9 Induced velocity versus blade radius for discretization

scheme assessment

82

6.1 Time accurate surface pressure coefficients at ψ=150 and

300; (a) & (b) are results from Boyd and (c) & (d) are from

current study

85



current study

86



current study

87

6.4 Variations in the simulated (Fluent 6.2) longitudinal inflow

ratio across the disk in forward flight as compared to

89

xiv

theoretical results of Mangler & Squire and experimental

results of Elliott & Althoff for μ=0.15





89





90

6.7 Variations in the simulated (Fluent 6.2) lateral inflow ratio

across the disk in forward flight as compared to theoretical

results of Mangler & Squire and experimental results of

Elliott & Althoff for μ=0.15

90





91





91

6.10 Thrust coefficient (CT) versus collective pitch angle

for main rotor blade

92

6.11 Induce velocity ratio along theblade for different collective

pitch angles

93

6.12 Comparison of induced velocity ratio between BEMT

prediction and current study

94

6.13 Variation of vertical drag on fuselage during hovering for a

revolution of main rotor blades

96

6.14 (a) Path Line colored by particle ID for V∞=0, 5 and 10 ms-1 98

6.14 (b) Path Line colored by particle ID for V∞=15, 20 and 25 ms-1 99

6.14 (c) Path Line colored by particle ID for V∞=30, 40, 50 and 60 100

xv

ms-1

6.15 3D view in frontal, side and top of the ROBIN model in

hovering

101

6.16 3D view in frontal, side and top of the ROBIN model of 5

ms-1 in forward flight

102



103



104



105



106



107



108



109



110

6.25 (a) Oil flow on the fuselage body for V∞=0, 5, 10, 15

and 20 ms-1

111

6.25 (b) Oil flow on the fuselage body for V∞=25, 30, 40, 50

and 60 ms-1

112

6.26 (a) Velocity vector colored by velocity magnitude for V∞=0

and 5 ms-1

113

6.26 (b) Velocity vector colored by velocity magnitude for V∞=10

and 15 ms-1

114

6.26 (c) Velocity vector colored by velocity magnitude for V∞= 20

and 25 ms-1

115

6.26 (d) Velocity vector colored by velocity magnitude for V∞=30

and 40 ms-1

116

xvi

6.26 (e) Velocity vector colored by velocity magnitude for V∞=50

and 60 ms-1

117

6.27 Vertical downforce on the isolated fuselage and rotor

fuselage in forward flight

119

xvii

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Configurations nomenclature for the three fuselage models 9

2.2 Summary of previous work sorted by year 25

5.1 Robin Body Shape Coefficient 69

5.2 ROBIN pylon shape coefficient 70

5.3 A Sample of calculation to solve the super ellipse equations

of ROBIN model

71

5.4 AS355 and ROBIN main rotor blades characteristics. 73

5.5 Total grids on the models 76

6.1 Data obtained from Aircraft Element Method for AS355 95

6.2 Location of blades and corresponding forces on the fuselage 96

6.3 Comparison between AEM and Fluent 6.2 predictions 96

xviii

NOMENCLATURE

Symbol

Definition

λ inflow ratio

A rotor disc area

TNCΔ Incremental of thrust over an element

iλ Local inflow ratio

lC α lift curve slope

TdCdr

Thrust gradient

dC drag coefficient

lC lift coefficient

F Induced velocity correction factor

TC thrust coefficient

c local chord length

E energy

cenfuuuv

Centrifugal force

D v vertical drag

dA area at typical element

corrfuuuuv

Corriolis force

ψ azimuth angle

TdC incremental of thrust

dT local thrust

d m•

mass flow rate

dr very small radius element

xix

q Dynamic pressure

f equivalent flat plat area

g gravity acceleration

dnC Drag coefficient at segment

An Segment area

TPPα Angle of tip path plane

μ Advance ratio

bN number of blade

R blade radius

r point position at the blade from the root

PU out-of-plane velocity component

rU resultant velocity

cV vertical free stream velocity

T total thrust

TU in-plane velocity component

V∞ freestream velocity

hv hovering induced velocity

iv induced velocity

α angle of attack

Ω rotor rotational speed ρ air density

rΔ radius elements of annulus

φ inflow ratio angle

θ collective pitch angle

TΔ increment of thrust on typical annulus

xx

Acronym Definition

CFD Computational Fluid Dynamic

NASA National Aeronautic & Space Administration

FUN3D Fully Unstructured Three Dimensional

V/STOL Vertical or Short Take Off Landing

ROBIN Rotor Body Interaction

LV Laser Velocimetry

LDV Laser Doppler Velocimetry

PIV Particle Image Velocimetry

BET Blade Element Theory

BEMT Blade Element Momentum Theory

GDWT Generalized Dynamic Wake Theory

CAD Computer Aided Design

PUMA Parallel Unstructured Maritime Aerodynamics

NLDE Non-Linear Disturbance Equation

EC120 Eurocopter Colobri Model 120

EC145 Eurocopter Colobri Model 145

AS355 Eurocopter Aerospatiale Model 355

RANS Reynolds Average Navier-Stokes

CHAPTER 1

INTRODUCTION

1.0 Background

Helicopter flight was probably the first type of flight envisioned by man. The

idea dated back to ancient China, where children played with homemade tops of

slightly twisted feathers attached to the ends of sticks. The flying Chinese top was a

stick with a propeller on top, which was spun by hands and released [1].

The helicopter, or direct lift airplane obtaining its support from the vertical

thrust of propeller turning in a horizontal plane instead of from the air reaction on

wings. Its most important advantage is its ability to rise vertically from a standing

start, eliminating the necessity for the long preliminary run characteristic of the

airplane. It offers the possibility of hovering motionless over a given spot, a feature

of tremendous usefulness for military purposes [2].

Helicopters have come a long way since the first ones flew in the early

twentieth century. Modern designs are capable of flying higher and faster than their

predecessors. In conjunction with the advances made thus far, tilt-rotors helicopter

will be expected to have even greater demands for improved performance and

reliability.

Recently, Universiti Teknologi Malaysia (UTM) has taken a big step to start

the study of helicopter technology through research and development and also

through the offering of the subject “helicopter technology” as an optional subject for

the final year degree of mechanical engineering (aeronautic) course. This is aimed at

http://www.centennialofflight.gov/essay/Dictionary/helicopter/DI27.htm

2

the fulfillment of the country's needs and in the long run to minimize the dependence

on foreign technology and expertise. The purchasing of the 2-seater helicopter is to

support teaching and learning and also for reverse engineering purposes. Faculty of

Mechanical Engineering, UTM has also formed a helicopter R&D group to design

and build a 4-seater helicopter as the first Malaysia made helicopter. The

aerodynamic and structural designs of helicopter are very vital and must be fully and

well understood. In order to reduce drag and also for good vertical take-off and fast

forward flight, the effect of interaction of flows from the helicopter main rotor to the

fuselage in vertical take-off and forward flight has to be studied in order to establish

the aerodynamics of the helicopter. This fact triggered the research that has been

taken and detailed in this thesis.

1.1 Problem Statement

It is well known that rotary wing aircraft aerodynamics is complicated.

Unlike fixed wing aircraft, on which a steady-state flight condition implies steady-

state aerodynamics, a rotary wing aircraft experiences a significant unsteady

aerodynamic environment in all flight conditions, even in level, unaccelerated flight,

due to the presence of the rotating wings. For fixed wing aircraft, the flow on the

fuselage body can be treated solely by free-stream velocity but in rotary wing

aircraft, both free-stream velocity and rotor wakes interact with the fuselage body.

Therefore, a study on the rotor-fuselage flow interaction is necessary in order to

understand the flow physics that leads to the proper aerodynamic design for the

fuselage body.

The rotor and fuselage interact in a complex, nonlinear fashion, making it

difficult to obtain reliable results from simple method. Most of the aerodynamic

research on helicopters done previously concerned with the prediction of the main

rotor forces and induced velocities. Aerodynamic analysis is important for

helicopters design because of unexpected aerodynamic behavior can affect the

aircraft in many ways, such as:

3

i. Performance: Poor aerodynamics reduces the aircraft’s ability to accomplish

its mission.

ii. Handling: Poor aerodynamics can also lead to reduced control system

effectiveness, degrading the stability characteristics of the aircraft.

iii. Vibration: The periodic aerodynamic loading can lead to structural vibrations

and can be a source of annoyance to the pilot.

iv. Maintenance: Unexpected aerodynamic loading can lead to increased fatigue

on components forcing them to require more frequent repair.

v. Noise: A variety of aerodynamic interactions can increase the noise generated

by the aircraft during operation.

Therefore, before any complicated design for a helicopter being done, one

must first determine the aerodynamic behavior of the helicopter especially of the

helicopter fuselage since the fuselage drag has been shown to account for up to one-

third of total helicopter drag [3]. In addition, the helicopter main rotor should be

included in any numerical simulation since rotor-fuselage interaction may have a

major influence on the helicopter flow field physics. The physics of the helicopter

flow field are shown below.

Figure 1.1: Flow structure and some aerodynamic problem areas on a helicopter in forward flight [4]

4

Rotor-fuselage flow interaction by experimental study which is normally

conducted by wind tunnel testing is very expensive and time consuming.

Computational method on the other hand has lately gained popularity as an

alternative tool. Furthermore, increased in computer storage capacity and

computation speed, increases the ability to simulate complex flow problem with high

accuracy and at less cost compare to experimental test. In this study, a commercial

CFD software from FLUENT Inc. is used since FLUENT had been widely used in

aeronautic and related industries. Moreover, UTM had already subscribed the

FLUENT software and there are a number of expert FLUENT users in the Faculty of

Mechanical Engineering that could be referred in time of necessity.

1.2 Research Objective

The main objective of the present research is to study and obtain rotor-

fuselage flow interaction both in hovering and forward flight. By understanding the

rotor-fuselage flow interaction, aerodynamic forces on the helicopter fuselage can be

determined, leading to a proper design of the helicopter fuselage.

1.3 Research Scope

The research work will cover the following scopes:

i. Theoretical determination of the aerodynamic characteristics of an existing

helicopter.

ii. Studying the governing equations, methods and assumptions in

Computational Fluid Dynamics (CFD) simulation.

iii. Using computational method to study and obtain flow characteristic of an

existing helicopter fuselage for the following conditions:

1. Isolated rotor blade during hovering and forward flight.

2. Isolated fuselage in forward flight.

3. Rotor with fuselage during hovering and forward flight.

5

1.4 Research Methodology

This research will be carried out as follow:

i. Literature review on the previous work of rotor-fuselage aerodynamics

ii. Theoretical analysis on helicopter aerodynamics; concentrating on the effects

of wakes and induced velocity of the rotor onto the helicopter fuselage

iii. Numerical analysis on helicopter in hovering and forward flight by using

FLUENT 6.2, a commercial CFD software package.

iv. Comparing the results obtained from theoretical and numerical analysis and

the previous work

1.5 Thesis Outline

This thesis is organized in seven chapters. The chapters are briefly described

as follows. Chapter 2 reviews the previous works on helicopter aerodynamics

generally. The works include the development of the theories, wind tunnel testing

and computer simulation for cases of helicopter rotor-fuselage flow interactions.

On the other hand, chapter 3 provides the basic theory of the helicopter

aerodynamics. The flow fields around the helicopter were studied by using

Momentum Theory, Blade Element Theory and Blade Element Momentum Theory.

Chapter 4 explains the governing equations in CFD. It also describes the

calculation method, turbulence modeling and commercial CFD software FLUENT

6.2. Chapter 5 describes how the simulation is carried out in FLUENT 6.2 including

the mesh boundary conditions and the methods used. It also provides the description

of the real helicopters and the simulation models.

Chapter 6 provides data comparison of the research and those of the previous

work. The comparison is carried out in order to validate the results obtained and the

method used. In this chapter the results of theoretical analysis and CFD for hovering

and forward flight are also presented. Lastly, chapter 7 summarizes the works that

have been done and provides concluding remarks for all the findings.

Recommendations for future study have also been provided.

a computational simulation of rotor...

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