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A thesis submitted in fulfillment of the requirement for the degree of Doctor of Philosophy (Engineering)

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AERODYNAMIC DESIGN AND STATIC STABILITY OF A HYBRID BUOYANT AIRCRAFT

BY

ANWAR UL HAQUE

A thesis submitted in fulfillment of the requirement for the degree of Doctor of Philosophy (Engineering)

Kulliyyah of Engineering

International Islamic University Malaysia

JANUARY 2017

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iii

ABSTRACT

Hybrid buoyant (HB) aircraft in which 50% of gross takeoff mass is supported by

“free of cost aerostatic lift”, are a new arena to boost up the tourism and agricultural industry by leveraging on the new merger of lighter than air and heavier than air technologies. Due to non-availability of historical trends for HB aircraft, which are required to begin with traditional method for aircraft design, it is quite difficult to estimate its aerodynamic and stability characteristics. In the present research work, correlation of the geometric and buoyant properties of the swimming animals with the HB flying vehicles has been done to link the existing modern knowledge of aerospace with the biological sciences. Fineness ratio, location of maximum width and buoyant independent drag of a California sea lion are found to be the three quantities which are common with hybrid buoyant aircraft. Based on the existing fundamental relationships used for aircraft as well as airship design, a new conceptual design methodology for such aircraft is proposed with the help of two design examples. Pugh concept selection charts have assisted to rank the population of different concepts of such aircraft.

Driving factors of such design concepts have been reviewed along with the selection of figure of merits. The diffused lift technology in HB aircraft seems to have eradicated the separate requirement of the heating mechanism for the lifting gas. A methodology for system design for consistent aerostatic lift is also proposed. The focus of this research work is not on the degree of “exactness” of the potential designs being considered at conceptual level, but rather to get the first- hand knowledge of the aerodynamics and static stability characteristics. Existing analytical relationships for the skin friction drag and Munk-Multhopp’s relationships for the estimation of pitching moment are revisited and potential issues related to their derivation are also elaborated. For the conceptual design work, Aircraft Digital DATCOM is used for a hybrid lift aerial vehicle. XFLR software along with the CFD results of the fuselage are used for HB aircraft, designed for STOL application. New analytical relationship for the estimation of the neutral point of a HB aircraft is derived. A first order approximation of the power-off stick fixed neutral point is done by using the computational results of the fuselage along with the panel method results for the lifting surfaces. The value so obtained is then compared with that obtained from the steady state simulations of the clean configuration of a two seater HB aircraft for which the SIMPLE scheme is employed for pressure velocity coupling along with the k-ω SST model. CFD results under predicts the slope of pitching moment as well as the static margin. Irrespective of the difference of flight and wind tunnel’s Reynolds number, a good comparison of results is obtained. However, from the controllability point of view, it’s negative sign can be made positive by designing an elevator for constant pitch down position for the level flight, moving the wing to further aft position or by increasing the anhedral angle of the canard. A chaotic behavior in the overall lift, drag and yawing moment is observed due to the dorsal fins. An increase in the aerodynamic coefficients is also observed when the configuration is tested after removing the dorsal fins. Moreover, an increase in the lateral stability is also observed when the canard is given a small anhedral angle. The developed databank of aerodynamic and static stability derivatives will be highly beneficial for the future design work of such aircraft after applying the Reynolds number corrections.

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iv

ثحبلا ةصلاخ

ABSTRACTIN ARABIC

ةنيجلها تارئاطلا تيلا يه

50 ةيئاولها اكيتاتسلاا نم معدب فيلاكت نودب ىتتأ اله عفرلا ةوقلا نم % يهو

برتعت

ةحاس ةديدج مجح ونم ةديازل نم ةيعانصلا ةعرازلاو ةحايسلا

للاخ ةدافتسلاا جمد نم

تاينقت ةيولجا ةديدلجا

ملعل فخلأا نازو لقثلأاو نم

تناايب رفوت مدعل ارظنو ءاولها ةيملع

ةييخرتا برتعت تيلا ةنيجلها تارئاطلا ريوطتل

ؤبنتلا بعصلا نم ناك ,ميمصتلا لحارم في دعاسم مهم لماع صئاصبخ

اكيمانيدلا ةيئاولها

و رارقتسلاا و ,

في

اذه لمعلا طبرلا تم يثحبلا ينب

صئاصلخا ةيسدنلها

عتمتت تيلا ابه

ةنيجلها ةيولجا تابكرلماو ةيرحبلا تنااويلحا

فراعلما طبرل كلذو ةكترشم صئاصخ ثلاث ىلع روثعلا تم ثيح ةيجولويبلا مولعلا عم نايرطلا لامج في ةثيدلحا

ضرعلا ليا لوطلا يهو ديطانلماو تارئاطلا ميمصت في مدختست تيلاو اينروفيلاك رحبلا دسأو ةنيجلها تارئاطلا ينب ( بيسنلا Fineness Ratio ( ةديازلاو ،ضرع ىصقا عقوم ،)

Buoyant ةقاعلاا في )

ضرع تمو،ةلقتسلما

تدعاسو تارئاطلا نم عونلا اذه ميمصتل ديدج يجهنم موهفم مادختسبا ينلاثم تاططخلما

( موهفلم ) Pugh في

دادعلاا فينصترايتخا ةفلتخلما

نم هذه دقو تارئاطلا تم

ضارعتسا لماوعلا

ةعفادلا ميهافلم ميمصتلا هذه ابنج لىإ

بنج عم رايتخا Figure of Merits ةمدختسلما ةينقتلاو

عفرل ت ةنيجلها تارئاطلا ودب

نهأ ةيلآ ىلع ةلصفنم ا

لما زاغلا ينخست حترق

ةيجهنم في ميمصت

ماظن Aerostatic و

لا زكري اذه لمعلا يثحبلا ىلع ةجرد "

ةقد هذه "

ميماصتلا ةلمتلمحا

تيلا يريج رظنلا اهيف ىوتسلما ثيح نم

، يرظنلا زكري انمإو

لوصلحا ىلع ىلع

تامولعم

ةيلوا ةرشابم نم اكيمانيدلا ةيئاولها

صئاصخو رارقتسلاا

ةتباثلا تم . ةعجارم تاقلاعلا ةيليلحتلا

ةمئاقلا يلع

كاكتحلاا يحطسلا

تاقلاعلاو Munk-Multhopp

ريدقت في ةمدختسلما نارودلا مزع

لكاشلماو ةلمتلمحا

ةقلعتلما تهاقاقتشبا ا

ثيح جمنارب مادختسا تم DATCOM

لمعل علاقلاا تاذ ةنيجه ةرئاط ندب ميمصت

يرصقلا طوبلهاو تايمجبرلا كلذكو ةيعارزلا لوقلحا نم ةعساش تاحاسم ةبقارم ضرغل STOL

XFLR ابنج

لىإ بنج عم جئاتن ةقلاعو CFD

ةيليلتح ةديدج ريدقتل ةطقن ةديامح ةرئاطل ثيح ةنيجه ةلداعم جاتنتسا تم

ةجردلا نم ةيبيرقت لولأا

كلذو ةتبثا ةدايق اصعل ةيعارش ةلاح في ةنيجه ةرئاطل ةديالمحا ةطقنلا ريدقتل مادختسبا

جئاتنلا ةيباسلحا نم

مسج ةرئاطلا مخضلا جئاتن عم ةقيرط

Panel Method تم ثم

ةنراقم ةميقلا تيلا تم

لوصلحا اهيلع

ططمخ مادختسبا ةاكالمحا جئاتن عم SIMPLE

ةقيرطب ناترقم k- ω SST

ىلع ةرئاط ةنيجه

نيدعقم تاذ ةرقتسم ءانبو .

ىلع ليلحتلا ةيباسلحا جئاتنلاو

نكيم ،ةيبيرجتلا جاتنتسا

نأ ةمخض ةرئاطلا ندب

ينجلها وه ببسلا سيئرلا مدع في رارقتسا

تبثا هاتجلاا يضرعلاو ليوطلا تاقتشلماو

رارقتسلا ةيلضافتلا

،نيوكسلا نوكتس جئاتنلا هذهو

تاذ ةدئاف ةيربك لامعلأ ميمصتلا يلبقتسلما

هذله

.تارئاطلا

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v

APPROVAL PAGE

The thesis of Anwar ul Haque has been approved by the following:

_____________________________

Waqar Asrar Supervisor

_____________________________

Erwin Sulaeman Co-Supervisor

_____________________________

Jaffar Syed Mohammed Ali Co-Supervisor

_____________________________

Ashraf Ali Omar Field Supervisor

_____________________________

Sher Afghan Khan Internal Examiner

_____________________________

Wirachman Wisnoe External Examiner

_____________________________

Fouad Mahmoud Mohammed Rawash Chairman

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vi

DECLARATION

I hereby declare that this dissertation is the result of my own investigations, except where otherwise stated. I also declare that it has not been previously or concurrently submitted as a whole for any other degrees at IIUM or other institutions.

Anwar ul Haque

Signature ... Date ...

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vii

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH

AERODYNAMIC DESIGN AND STATIC STABILITY OF HYBRID BUOYANT AIRCRAFT FOR TOURISM AND

AGRICULTURE PURPOSES

I declare that the copyright holders of this dissertation are jointly owned by the student and IIUM

Copyright © 2017 by Anwar ul Haque and International Islamic University Malaysia.

All Rights Reserved.

No part of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder except as provided below.

1. Any material contained in or derived from this unpublished research may only be used by others in their writing with due acknowledgement.

2. IIUM or its library will have the right to make and transmit copies (print or electronic) for institutional and academic purposes.

3. The IIUM library will have the right to make, store in a retrieval system and supply copies of this unpublished research if requested by other universities and research libraries.

Affirmed by Anwar ul Haque

... ...

Signature Date

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viii

ACKNOWLEDGEMENTS

First and foremost I am grateful to the Almighty from whom I get the strength to live, learn, grow and excel. I owe every success to Him as He gives me the courage to rise up from failures and difficulties. I am grateful to my late parents, who formed part of my vision and taught me the good things that really matter in life, for their endless prayers and boundless love, specially my father who inculcated in me the desire to seek knowledge for a greater purpose and allowed me to pursue my interests by supporting me in every way he could to accomplish my goals.

A great teacher is one who not only quenches student’s thirst for knowledge but instills more profound thirst by making him realize his ignorance. I am extremely fortunate to have Prof. Waqar Asrar as my supervisor in Ph.D. He helped me understand the foundations of the subject as well as motivated me in my pursuit for Ph.D. This dissertation could not have been possible without Prof. Waqar Asrar, who encouraged me throughout my academic program. He has been guiding me to achieve my goal by making me discover my own capabilities.

I am extremely fortunate to have people like Professor Ashraf Ali Omar, Dr. Erwin Sulaeman and Dr. J.S Ali, who reviewed my work and I am thankful to them for their guidance and support. I am also thankful to Dr. Willem Anemaat, Dr. Daniel P.

Raymer, Prof. Barry Prentice, Prof. Ning Qin, Prof. Frank A. Fish, Prof. Steven Vogel, Prof. Dr. Robert Rist, Prof. Snorri Gudmundsson, Prof. Brandon T. Buerge, Dr. Anabela Maia, Dr. Muhammad Asif, Dr. Qasim Zeeshan and Dr. Mengmeng Zhang for providing me guidance in solving the technical queries.

I thank all my teachers and mentors, who guided me throughout my life and made it possible for me to reach where I stand today, and among them especially Prof. Ning Qin and Prof. Khalid Pervez and Dr. Atiq-ur-Rahman (Late). I am thankful to Dr.

Dadang and his team for successfully carrying out the manufacturing of the sub-scaled model as per the provided design specifications. Special thanks to Mrs. Azliza Binti Embong, Senior Engineer IIUM-LSWT and her team for providing assistance in the experimental work.

I would like to thank Ministry of Science, Technology and Innovation (MOSTI), Malaysia for providing me with the financial support for my study. To partially reward this generous support, I hope I would be able to participate in the progress of my organization and country. I must give profound thanks to all the people in my office, which showed faith in me, especially Dr. Raza Samar, Dr. Sajid Raza Ch., Mr.

Muhammad Junaid, Mr. Nadeem Javed, M. Abdul Jabbar and Dr. Waqar Azim.

I must give profound thanks to all my friends and colleagues here and back home, especially Aldeeb, Dr. Naveed Durrani, Dr. Uzair Dar, Dr. Hassan Junaid, Mr. Farooq Umar, Mr. Harris Hammed and Mr. Ammar Bin Shaukat for their encouragement.

Last but not the least; I would like to thank my family who form the backbone of my life and origin of my happiness. My deepest admiration for my wife, who did more than her share around the house as I sat on the computer. To my daughter, I thank you for the joy you bring to my life and I hope this will be a legacy for you to pursue your dreams no matter how long it takes or how great is the challenge.

May God bless you All.

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TABLE OF CONTENTS

Abstract ... III Abstract in Arabic ... IV Approval Page ... V Declaration ... VI Acknowledgements ... VIII Table of Contents ... IX List of Tables ... XII List of Figures ... XIII List of Symbols ... XVII

CHAPTER ONE: INTRODUCTION ... 1 Background ... 1 1.1

History of Hybrid Buoyant a Aircraft ... 2 1.2

Aerodynamic Design ... 5 1.3

Static Stability ... 7 1.4

Research Motivation ... 8 1.5

Problem Statement ... 11 1.6

Research Objectives... 17 1.7

Research Outcomes and Limitations ... 17 1.8

Major Contributions ... 17 1.8.1

Limitations ... 18 1.8.2

CHAPTER TWO: LITERATURE REVIEW ... 21 Introduction... 21 2.1

Aerostatic and Aerodynamic Lift ... 26 2.2

Aerostatic Lift ... 26 2.2.1

Aerodynamic Lift ... 27 2.2.2

Reference Area to Non-Dimensionalized the Forces ... 28 2.2.2.1

Fineness Ratio: ... 30 2.2.2.2

Analytical Techniques... 31 2.2.2.3

Form Factor ... 32 2.2.2.4

Utilization of Low Fidelity Tools ... 32 2.2.2.5

Static Stability ... 33 2.3

Analytical Technique ... 34 2.3.1

Wind Tunnel Testing ... 36 2.4

Blockage Correction ... 37 2.4.1

CHAPTER THREE: METHODOLOGY ... 41 Introduction... 41 3.1

Aerodynamic Contour Design ... 41 3.2

Hybrid Buoyant Aerial Vehicle (Configuration I) ... 43 3.2.1

Hybrid Buoyant Aircraft (Configuration II) ... 45 3.2.2

Array of Initializing Parameters for Performance Analysis ... 49 3.2.3

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Static Stability Analysis ... 51 3.3

Wind Tunnel Testing ... 52 3.4

CHAPTER FOUR: CONFIGURATION DESIGN AND ITS SELECTION ... 55 Introduction... 55 4.1

Framework of Methodology ... 55 4.2

Conceptual Design Cycle ... 57 4.3

Driving Factors for Conceptual Design ... 58 4.3.1

Conceptual Configuration Alternatives (CCA) ... 61 4.4

Implementation of Pugh Analysis ... 62 4.4.1

Hydrodynamic Characteristics of a Marine Animal ... 65 4.4.2

Aerostatic Vis-A-Vis Aerodynamic Modules ... 67 4.5

Aerostatic Module ... 68 4.5.1

Net Weight ... 69 4.5.1.1

Revised Formula for Gross Take off Mass Estimation .. 70 4.5.1.2

Operational Empty Mass ... 73 4.5.1.3

Volume of Hull ... 74 4.5.1.4

Aerodynamic Module ... 76 4.5.2

Wing Loading ... 77 4.5.2.1

Summary ... 78 4.6

CHAPTER FIVE: RESULTS AND DISCUSSIONS ... 83 Introduction... 83 5.1

Potential Issues in Analytical Relationships ... 83 5.2

Form Factor ... 83 5.2.1

Reference Area ... 85 5.2.2

Analytical Relationships ... 85 5.2.2.1

Proposed Reference Area ... 88 5.2.2.2

Test Case of a Hybrid Lifting Hull ... 88 5.2.2.3

Test Case of a Generic Model of Transport Aircraft ... 91 5.2.2.4

Static Longitudinal Stability ... 93 5.2.3

Test Case of a Hybrid Lifting Hull ... 94 5.2.3.1

Test Case of a Wing Fuselage Generic Model ... 96 5.2.3.2

Use of Analytical Tools in Configuration Design ... 97 5.3

Aerodynamics ... 97 5.4

Hybid Buoyant Aerial Vehicle (Configuration-I) ... 97 5.4.1

Hybrid Buoyant Aircraft (Configuration-II) ... 99 5.4.2

Static Stability ... 100 5.5

Analytical Formulation for Estimation of Neutral Point ... 101 5.5.1

Static Stability of Configuration-I ... 102 5.5.2

Static Stability of Configuration-II ... 105 5.5.3

Configutaion Details ... 107 5.6

Configuration-I ... 107 5.6.1

Configuration-II ... 108 5.6.2

CFD Analysis of Configuration-II ... 110 5.7

Performance Analysis ... 118 5.8

Impact of Buoyancy Ratios on Aerodynamic Ratios ... 118 5.8.1

Performance and Trim Analysis ... 120 5.8.2

Findings ... 123 5.8.2.1

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Wind Tunnel Testing ... 125

5.9 Strut Tare Interference ... 126

5.9.1 Hybrid Lifting Fuselage (HLF)-Generic ... 127

5.9.2 Experimental Setup and Model Description ... 127

5.9.2.1 Aerodynamics and Static Stability Derivatives ... 128

5.9.2.2 Findings ... 132

5.9.2.3 Hybrid Buoyant Aerial Vehicle ... 133

5.9.3 Model Design and Scaling for Wind Tunnel Testing .. 133

5.9.3.1 Comparison of Winged and Wingless Model ... 135

5.9.3.2 Canard of a HB Aircraft ... 138

5.9.4 Details of the Geometry ... 140

5.9.4.1 Test Results - With Gap ... 140

5.9.4.2 Test Results - Without Gap ... 142

5.9.4.3 Hybrid Buoyant Aircraft ... 143

5.9.5 Aerodynamic and Static Stability Derivatives ... 144

5.9.5.1 Results of Canard Settings ... 145

5.9.5.2 Reflexed Canard Case ... 148

5.9.5.3 Directional Stability ... 149

5.9.5.4 Effect of Dorsal Fins on Directional Stability ... 152

5.9.5.5 Comparison of the CFD and Wind Tunnel Data ... 154

5.9.5.6 Asymmetric Thrust Due to Propellers ... 157

5.9.6 CHAPTER SIX: CONCLUSION AND RECOMENDATIONS ... 161

Conclusion ... 161

6.1 Few Recommendations for Future Work ... 167

6.2 REFERENCES ... 171

LIST OF PUBLICATIONS ... 180

ACHIEVEMENTS ... 184

APPENDIX-A: PEST ANALYSIS ... 186

APPENDIX-B: HYDRODYNAMIC PROFILE OF CALIFORNIA SEA LION .... 189

APPENDIX-C: ESTIMATION OF GROUND ROLL DISTANCE ... 191

APPENDIX-D: ISSUE OF AEROSTATIC LIFT ... 193

APPENDIX-E: VOLUMETRIC FRACTIONS OF MASS OF HB AIRCRAFT .... 196

APPENDIX-F: WEIGHTS OF MAJOR PARTS OF HB AIRCRAFT ... 199

APPENDIX-G: ISSUE OF FUNDAMENTAL DRAG EQUATION ... 201

APPENDIX-H: REVISED FORMULAE FOR POWER REQUIRED ... 203

APPENDIX-I: MATLAB CODE ... 206

APPENDIX-J: DERIVATION OF MUNK-MULTHOPP’S FORMULA ... 210

APPENDIX-K: ANALTICAL RELATIONSHIP FOR NEUTRAL POINT ... 212

APPENDIX-L: HALF MODEL TESTING OF CANARD OF HB AIRCRAFT .... 216

APPENDIX-M: EFFECTIVE TEST SECTION AREA FOR BLOCKAGE ... 219

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LIST OF TABLES

Table No. Page No.

Table 1.1 Few major HB Aircraft/HBAV 4

Table 1.2 Specifications of Short Range Aircraft 7

Table 1.3 Details of the Experimental Testings 16

Table 2.1 Comparison of Definitions of Reference Area 30

Table 3.1 Ferry Range between Kuala Lumpur and nearby Islands 43

Table 3.2 Fineness Ratio of Non-Rigid Airships 45

Table 3.4 Performance Parameters of HB aircraft 48

Table 3.5 Procedure followed in XFLR® to Analyze HB Aircraft 49 Table 3.6 Array of Input Matrix of Different Sub Modules 50 Table 3.7 Methodology for the Estimation of Asymmetric Thrust 54 Table 4.1 Major Advantages and Disadvantages of Potential Configurations 63

Table 4.2 Pugh Matrix 65

Table 4.3 Breakdown of Approximate Gross Take-off Mass (kg) 71 Table 4.4 Comparison of Masses and Mass Fractions of Small Aircraft 72

Table 5.1 Comparison of Geometric Parameters 87

Table 5.2 Calculations Done for Different Choices of Reference Area 89

Table 5.3 Comparison of Analytical and CFD Results 95

Table 5.4 Major Geometric Parameters 108

Table 5.5 Major Geometric Parameters of Configuration-II 110 Table 5.6 Comparison of Aircraft Digital DATCOM and Wind Tunnel Results 138

Table 5.7 Comparison of Results-HB Aircraft 156

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LIST OF FIGURES

Figure No. Page No.

Figure 1.1 Schematic Views of Hornet AW, (Blake, 2013) and ESTOLAS 3 Aircraft, (Gamaleyev, 2012)

Figure 1.2 Research Outcomes 20

Figure 2.1 Major References Used in This Thesis 22

Figure 2.2 Plots of Drag coefficient and Gross Power as Function of Fineness 32 Ratio, (Ilieva, et.al, 2014)

Figure 3.1 Flow Chart of the Approach Adopted to meet Research Objectives 41 Figure 3.2 Methodology adopted for Configuration Selection - Pugh Method 42 Figure 3.2 Methodology Adopted for Calculation of Wing Loading 47

Figure 3.3 Framework for Static Stability Analysis 51

Figure 3.4 Roadmap followed for the Wind Tunnel Testing 53 Figure 4.1 Flow Chart of Proposed Methodology for Conceptual Design 56

Figure 4.2 Initial Sketches of Different HB Aircraft 57

Figure 4.3 Pictorial View of Shapes of Hull 59

Figure 4.4 Results of Static Stability Analysis of a Winged Hybrid Airship 61 Figure 4.5 Sketches of Few HB aircraft’s Configurations 62 Figure 4.6 Experiments done on a California Sea Lion in Zoo Nigara 67 Figure 4.7 Effect of Coefficient of Buoyant Lift Due to Change in Altitude 69

Figure 4.8 Constrained Carpet Plot Based on mnet 69

Figure 4.9 Flow Chart of the Proposed Methodology 80

Figure 5.1 Variation in Form Factor (FF) due to Change in Fineness Ratio 84

Figure 5.2 Comparison of FF 85

Figure 5.3 Schematic views of HLF of a HB aircraft 88

Figure 5.4 Different views of Grid and the Contours of Coefficient of Pressure 90

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Figure 5.4 Generic model of a Transport Aircraft 91

Figure 5.5 Comparison of CL vs  92

Figure 5.6 Variation in CL with  for Different Choices of Reference Area 92 Figure 5.8 Implementation of Munk-Multhop method on HLF 95 Figure 5.9 Estimation of 𝐶𝑚∝

𝑓𝑢𝑠 of a Generic Model 97

Figure 5.10 Schematic Views of Planform and Frontal Area 98

Figure 5.11 Plot of CD vs 98

Figure 5.12 Plot of CL vs  99

Figure 5.13 Modeling and Simulation Results of XFLR 100

Figure 5.14 Lift Characteristics of a HB Aircraft 100

Figure 5.15 Major Components Contributing to the Estimation of Neutral Point 101

Figure 5.16 Cm vs  plot for different CG Locations 103

Figure 5.17 Contribution of different Components Towards Static Stability 103 Figure 5.18 Top View of HBAV to show the Location of CG 105 Figure 5.19 Plots of Static Stability Derivatives of a HBAV 106 Figure 5.20 Arrangement of Ballonets Inside the Fuselage 107

Figure 5.21 Isometric View of a HBAV Configuration 108

Figure 5.22 Inspiration from Nature for HB Aircraft’s Design 109 Figure 5.23 Schematic Views to Show the Surface Grid and Grid Clustering 113 Figure 5.24 Lift and Drag Contribution Obtained from CFD 113

Figure 5.25 CFD Results of Aerodynamic Coefficients 114

Figure 5.26 Flow Visualization Results of CFD 115

Figure 5.27 Cm vs  Plot to show Contribution of Individual Components 116 Figure 5.28 Cm vs  Plot to Show the Effect of Deflection of Canard 117 Figure 5.29 Streamline Plot with Contours of Total Pressure (Pa) 118 Figure 5.30 Effect of 𝜆𝐴 on Important Aerodynamic Ratios 119

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Figure 5.31 Required and Available Thrust (N) vs Velocity (m/s) 120 Figure 5.32. Plot of Power Available and Required Power vs Velocity 121

Figure 5.33 Plot of (𝑅/𝐶)𝑚𝑎𝑥 in m/s vs Altitude (m) 122

Figure 5.34 Area under the Curve to find Time Required for (𝑅/𝐶)𝑚𝑎𝑥 122

Figure 5.35 Maximum Load Factor for Instantaneous Turn 122

Figure 5.36 Plot of Trim Analysis 124

Figure 5.37 Side Views of HB Aircraft for Different Positions of Gondola 124

Figure 5.38 Wake produced by Strut at  = 20 m/s 126

Figure 5.39 Forces and Moments of Strut at V=50 m/s 126

Figure 5.40 Pictorial Views of 𝑊1𝑀0and 𝑊1𝑀1 Tests 128

Figure 5.41 Experimental Results of HLF 130

Figure 5.42 Splitted Views of the Triaxial Ellipsoidal Shaped Hull of a HBAV 134

Figure 5.43 Scaled down Model of a HBAV in IIUM-LSWT 134

Figure 5.44 Wingless Model Tested in IIUM Wind Tunnel 136

Figure 5.45 Comparison of Results - Wingless vs Winged Model of HBAV 137 Figure 5.46 Geometric details of the Scaled Down model of Canard 140

Figure 5.47 Canard Model Tested in IIUM-LSWT 141

Figure 5.48 Variation in CD vs  142

Figure 5.49 Variation in CL vs  143

Figure 5.50 Different Components of a HB Aircraft Model 144

Figure 5.51 Canard Settings of a HB Aircraft 145

Figure 5.52 Impact of Anhedral Angle of Canards for  Sweep at V=25 m/s 146 Figure 5.53 Impact of Anhedral Angle of Canards for  Sweep at V=35 m/s 147 Figure 5.54 Impact of Anhedral angle of Canards for Sweep at V=45 m/s 148 Figure 5.55 Impact of Cambered Profile of Canards for  Sweep at V=25 m/s 149 Figure 5.56 Impact of Anhedral Angle of Canards for  Sweep at V=25 m/s 150

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Figure 5.57 Impact of Anhedral Angle of Canards for  sweep at V=35 m/s 151 Figure 5.58 Impact of Anhedral Angle of Canards for  sweep at V=45 m/s 151 Figure 5.59 Effect of Dorsal Fins for  sweep at V=25 m/s 153 Figure 5.60 Effect of Dorsal Fins for  sweep at V=35 m/s 154 Figure 5.61 Effect of Dorsal Fins for  sweep at V=45 m/s 154

Figure 5.62 Comparison of CFD and Wind Tunnel Results 155

Figure 5.63 Role of the Dorsal Fin in Controlling the Asymmetric Thrust 158

Figure 5.64 Plot of CL as Function of  159

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xvii

LIST OF SYMBOLS

𝐴𝑓𝑟𝑜𝑛𝑡_ℎ𝑢𝑙𝑙 frontal area of hull 𝐴𝑅ℎ aspect ratio of hull 𝐴𝑅𝑤 aspect ratio of wing

a semi-major axis, m

a.c aerodynamic center, m

b semi-minor axis, m

𝑏𝑤 wing span of wing, m

𝐵𝑅 buoyancy ratio

𝐶𝑏ℎ𝑝 engine specific fuel consumption 𝐶𝑓 skin friction drag

𝑐𝑤 mean aerodynamic chord of wing, m

𝐶𝐿𝑐𝑟𝑢𝑖𝑠𝑒 aerodynamic lift coefficient at the cruise condition 𝐶𝐿𝑚𝑎𝑥

𝑎𝑒𝑟𝑜 maximum aerodynamic lift coefficient

𝐶𝐿𝑚𝑑 coefficient of aerodynamic lift for the minimum drag 𝐶𝐷𝑂 zero-lift drag coefficient

𝐶𝐷𝑚𝑖𝑛 coefficient of minimum drag CFD computational fluid dynamics 𝐶𝑚 coefficient of pitching moment 𝐶𝑚𝑜 slope of pitching moment, (/degree)

FF form factor

FR fineness ratio

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xviii

GA general aviation

𝐻𝑐 pressure height, m

HB hybrid buoyant

𝑖𝑓 fuselage camber incidence angle, degree

IC internal combustion

K drag due to lift factor 𝑙⁄𝑑 lift to drag ratio of airfoil

lgond length of gondola, m LSWT low speed wind tunnel 𝐿𝑎𝑒𝑟𝑜𝑡𝑜𝑡 total aerodynamic lift, N

𝐿𝑎𝑒𝑟𝑜𝑤 aerodynamic lift force generated by wing, N 𝐿𝑎𝑒𝑟𝑜ℎ aerodynamic lift generated by hull’s contour, N

(𝐿𝑎𝑒𝑟𝑜

⁄ )𝐷

𝑚𝑎𝑥 aerodynamic lift to drag ratio

Lht distance between a.c of wing and a.c of horizontal tail, m

Lvt distance between a.c of wing and a.c of vertical tail, m LTA lighter than air

M Mach number

mg mass of lifting gas, kg empty

m empty mass , kg

mGTM total mass corresponding to gross takeoff mass, kg

madd added mass, kg

accel

m full accelerated mass, kg

miaee mass of avionics group, kg

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xix

𝑚𝐺𝑇𝑊 total mass corresponding to gross takeoff weight, kg 𝑚𝑓𝑡𝑟𝑎𝑝𝑝𝑒𝑑 mass of fuel trapped in engine and fuel tank, kg MRC moment reference center, m

N time for rotation, revolution per minute

Nen number of engines Npax number of passengers

Ncrew number of crew

cruise

q dynamic pressure under cruise conditions, Pascal R universal gas constant, (J/mol. K)

𝑅𝑒 Reynolds number

𝑅𝑒

⁄𝑙 Reynolds number per unit chord length STP standard temperature and pressure STOL short take-off and landing

𝑆𝑟𝑒𝑓 reference area, m2 𝑆𝐺 𝑇𝑂 take off ground roll, m

𝑉𝑜𝑙 volume, m3

𝑉𝑜𝑙𝑓 volume of fuel, m3 VT vertical tail

𝑉𝑐𝑟𝑢𝑖𝑠𝑒 cruise velocity, m/s 𝑉𝑠𝑡𝑎𝑙𝑙 stall velocity, m/s 𝑉𝑚𝑎𝑥 maximum velocity, m/s 𝑉𝐿𝑂 velocity for lift-off, m/s 𝑊𝑒𝑛 weight of engine, N

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xx 𝑊𝑂 weight at start of mission segment, N 𝑊𝑂𝑀𝑂 wind-off and model-off condition 𝑊𝑂𝑀1 wind-off and model-on condition 𝑊1𝑀1 wind-on and model-on condition 𝑊1 weight at end of mission segment, N

𝑊𝑛𝑒𝑡 net weight, N (W also has the same meanings) 𝑊𝐺𝑇𝑊 gross takeoff weight, N

𝑊𝑓 fuel weight, N

𝑊𝑎𝑢𝑥 weight corresponding to mass of auxiliary items, N 𝑤𝑔𝑜𝑛𝑑 width of gondola, m

 angle of attack, degree

𝑂𝐿 angle of attack corresponding to zero lift condition, degree

𝑍𝐿 𝑤 wing zero-lift angle relative to the fuselage reference line, degree

 side-slip angle, degree

𝑘2− 𝑘1 correction factor to account for the fuselage slenderness ratio λA. designed ratio of ∆W to total weight, 0< λA <1

 rolling resistance due to friction

 wing sweep angle at 25% of mean aerodynamic chord

𝐻 density of air at pressure altitude, kg/m3

𝑆𝐿 density of air at sea-level, kg/m3

𝑓 density of fuel used by reciprocating engine, kg/m3

%𝐹 percentage of air inflation 𝛿 boundary layer thickness, mm

𝛿 boundary layer displacement thickness, mm

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LIST OF ABREVIATIONS

CFD Computational Fluid Dynamics GA General Aviation

HB Hybrid Buoyant IC Internal Combustion LSWT Low Speed Wind Tunnel LTA Lighter Than Air

STP Standard Temperature and Pressure STOL Short Takeoff and Landing

XXI

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1

CHAPTER ONE INTRODUCTION

Do they not see the birds controlled in the atmosphere of the sky? None holds them up except Allah. Indeed in that are signs for people who believe.

Quran (76:19)

BACKGROUND 1.1

With the passage of time, number of people travelling by air for tourism has increased.

Hybrid Buoyant (HB) aircraft, getting aerodynamic lift from the lifting surface, including the voluminous fuselage and partially supported by buoyancy lift generated by the buoyant gas can offer a travelling option with lesser fuel emission. Most of the international airports are away from city center and sometimes it takes long to reach the destination. Passengers, specially the tourists can be facilitated by deploying such hybrid buoyant aircraft as ‘Airport-City Center Transfer’. It is well known that palm oil, rubber, rice, timber, coconuts, pepper, cocoa and subsistence crops are Malaysia’s main agricultural products. These agricultural products require a monitoring as well as fast control/elimination mechanism for unwanted pests. Conventional methods for the said purpose include a sprayer i.e. a piece of equipment that is used to apply herbicides, pesticides, and fertilizers on agricultural crops. One of the potential reasons is the technological gap for developing the sophisticated technologies for spraying the agricultural land. Since the profession of farming operation is counted in low income levels, therefore, most of the farmers rely on old technology of farm spraying by the individuals. This issue becomes more serious where human access is not so easy for monitoring the crops, especially on hilly places like Cameron

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2

Highlands. Under such circumstances a hybrid buoyant aerial vehicle (HBAV) can provide a unique solution due to slow flying speed and the limitation of flying height which is function of the pressure height.

For aircraft, the volume of fuselage is quite small as compared with that of the hull of an airship, and a hull’s structural anatomy is also quite different from that of an aircraft’s fuselage. The huge volume of the hull and its aerostatic lift are the two fundamental parameters which differentiate buoyant and hybrid buoyant vehicles and aircraft. Moreover, all airships takeoff and land with the help of vertical takeoff and landing (VTOL) technology, but HB aircraft can takeoff similar to an aircraft. Helium is commonly used as the lifting gas to provide the buoyant lift. It is important to note that if the lifting gas bag can freely expand or contract then the aerostatic lift remains consistent till pressure altitude, (Raymer, 2012). Therefore, load balanced by the hydrodynamic lift will remain constant till pressure height.

HISTORY OF HYBRID BUOYANT AIRCRAFT 1.2

The concept of buoyancy has already given birth to HB aircraft. AEREON, a delta shaped buoyant aircraft was among the first one which was tested in late 1975 by (Putman, 1973). This aircraft was designed such that the control surfaces and propulsion system were placed at the tail of the hull. In recent years many different configurations have been designed and developed for transportation and disaster management. These aircraft are mostly in design, testing and experimental phase and are always in semi buoyant condition (Blake, 2013; Gamaleyev, 2012; Rist, 2012).

Among these is Dynalifter by (Rist, 2012), a plane disguised as an airship, whose fuselage and wing provides half of the total lift; its prototype was flown in late 2012.

Hornet Light Utility and Hornet AW are two aircraft by (Blake, 2013) which also

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3

fulfill partial requirement of lift with the help of wings. Both of them have two engines which are attached to the wing. Hornet AW is a two seater aircraft, Figure 1.1(a). It can fly till 7000 ft and can attain maximum velocity of 150 km/hr.

ESTOLAS by (Gamaleyev, 2012) is another hybrid buoyant aircraft designed for extremely short takeoff and landing on all surfaces, Figure 1.1(b). Dynalifter, a prototype of a cargo plane disguised as an airship, is another semi-buoyant ultralight aircraft developed by (Rist, 2012). Other promising designs include Aeroscraft, (Aeros, 2012), (Sky Freighter, 2012) and Lockheed’s LEMV, (Harrison, 2011). All such concepts are tabulated in Tab 1.1 for quick reference. Unfortunately, not much is known about the aerodynamic design of HB aircraft (manned or autonomous) and their aerodynamic and stability characteristics have not yet been fully explored in open literature. The main cause of this is probably the non-availability of historical trends required to get the aerodynamic and stability data, which is a pre-requisite to begin such studies. Hence, there is a need to fill in the gap, specially methodology, conceptual design and experimental data for estimation of its aerodynamic and stability characteristics. The said gap can only be filled after conducting an exercise at conceptual level for aerodynamic contour design followed by comprehensive wind tunnel testing to get confidence in utilization of low fidelity design tools.

(a) Hornet AW (b) ESTOLAS

Figure ‎1.1 Schematic Views of Hornet AW, (Blake, 2013) and ESTOLAS Aircraft, (Gamaleyev, 2012)

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4

Table ‎1.1 Few Major HB Aircraft/HBAV

Name References

M2-F (Gumse, 1967)

Megalifter (Bruno & Joner, 1975) P-791 (Harrison, 2011)

Aeroship (Liu, Liou & Schulte, 2009) IIUM-WHA (Andan, Asrar, & Omar, 2012) Dynalifter (Rist, 2012)

ESTOLAS (Gamaleyev, 2012) Solarship (Solarship, 2014) MAAT (Ilieva, et. al., 2014)

For the case of hybrid airships, a few individuals and groups have proposed a limited variety of hybrid concepts for airships in the past few years like (Agte et al., 2010; Liu, Liou, & Schulte, 2009; Mackrodt, 1980) for surveillance and cargo transportation as well, but nothing beyond a demonstration model has been built. If we look back in the history, the first lifting-body concepts involved very blunt half-cones, (Becker, 1958). Later, the concepts evolved into higher fineness- ratio cones to achieve the capability of an unpowered horizontal landing, (Saltman, Wang & Iliff, 1999). Numerous wind-tunnel model tests were performed on candidate versions of the half-cone and shapes having flattened bottom surfaces. In 1962, (Raeed & Lister, 2002) had provided the details of unpowered horizontal landings and controllable flight with a miniature lightweight radio controlled model of an M2 half-cone configuration. Unfortunately, none of them have explored an airfoil shaped hull from the aerodynamic and stability point of view. In the case of hybrid airships, as per (Carichner & Nicolai, 2013), there is no experimental data available for aerodynamic lift generated by the hull and its stability characteristics. Most of the experimental data

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