Computational Aeroacoustic Investigation of Co-rotating rotors for Urban Air Mobility. The presentation is split into different slides (for pdf format) corresponding to different animations. Master of Science in Aerospace Engineering, specializing in Aerodynamics, Aeroacoustics, and Wind Energy at TU Delft, the Netherlands.

1. 1
MSc Thesis
Shubham
Aeroacoustics group
Wind Energy
Faculty of Aerospace Engineering

2. 2
Traffic problems…
1inrix.com/scorecard/
1

3. 3
Traffic problems…
• London
– population of 8.9 million
– hours wasted in traffic/year - 2271
1inrix.com/scorecard/
1

4. 4
Traffic problems…
• London
– population of 8.9 million
– hours wasted in traffic/year - 2271
• Paris
– population of 2.1 million
– hours wasted in traffic/year - 2371
1inrix.com/scorecard/
1

5. 5
Traffic problems…
• London
– population of 8.9 million
– hours wasted in traffic/year - 2271
• Paris
– population of 2.1 million
– hours wasted in traffic/year - 2371
• United States
– report by Texas Transportation Institute
– loss - $78 billion/year2
1inrix.com/scorecard/ 2Issues of the Day, Ian W.H. Parry and Felicia Day, 2010
1

6. 6

7. 7

8. 8

9. 9
Urban Air Mobility

10. 10
Urban Air Mobility
• Urban transportation system
Image courtesy: NASA/Lillium/Uber/Hyundai

11. 11
Urban Air Mobility
• Urban transportation system
• Personal Air Vehicle (PAV)
Image courtesy: NASA/Lillium/Uber/Hyundai

12. 12
Urban Air Mobility
• Urban transportation system
• Personal Air Vehicle (PAV)
– Transport of people and goods
Image courtesy: NASA/Lillium/Uber/Hyundai

13. 13
Personal Air Vehicle
Image courtesy: Uber/Hyundai

14. 14
Personal Air Vehicle
• Requirements:
Image courtesy: Uber/Hyundai

15. 15
Personal Air Vehicle
• Requirements:
– Electric operated
Image courtesy: Uber/Hyundai

16. 16
Personal Air Vehicle
• Requirements:
– Electric operated
– High efficiency
Image courtesy: Uber/Hyundai

17. 17
Personal Air Vehicle
• Requirements:
– Electric operated
– High efficiency
– Low noise
Image courtesy: Uber/Hyundai

18. 18
Personal Air Vehicle
• Requirements:
– Electric operated
– High efficiency
– Low noise
– Safety factors
Image courtesy: Uber/Hyundai

19. 19
Personal Air Vehicle
• Requirements:
– Electric operated
– High efficiency
– Low noise
– Safety factors
Image courtesy: Uber/Hyundai

20. 20
Personal Air Vehicle
– High efficiency
– Low noise
Image courtesy: Uber/Hyundai
Aerodynamic

21. 21
Personal Air Vehicle
– High efficiency
– Low noise
• Aerodynamic noise: Aeroacoustics
Image courtesy: Uber/Hyundai
Aerodynamic

22. 22
Aeroacoustics
• Noise generated by aerodynamic flows

23. 23
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility

24. 24
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors

25. 25
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors

26. 26
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?

27. 27
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?
• Types of rotors:

28. 28
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?
• Types of rotors:
– Co-planar rotor
Image courtesy: GetFPV

29. 29
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?
• Types of rotors:
– Co-planar rotor
– Contra-rotating rotor
Image courtesy: Workhorse

30. 30
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?
• Types of rotors:
– Co-planar rotor
– Contra-rotating rotor
– Tandem rotor
Image courtesy: Boeing

31. 31
Aeroacoustics
• Noise generated by aerodynamic flows
• Key factor in Urban Air Mobility
• Major noise source – Rotors
• Can we increase efficiency and
decrease noise for a rotor, even further?
• Types of rotors:
– Co-planar rotor
– Contra-rotating rotor
– Tandem rotor
– Co-rotating rotor
Image courtesy: Myself

32. 32
Co-rotating rotor
Top view Side view
• 𝜙 : angular separation
• 𝑧 : axial separation
• n : rotations per second (rps)
Orthogonal view

33. 33
Co-rotating rotors
Aeroacoustic
Urban Air Mobility

34. 34
Computational Aeroacoustic Investigation of
Co-rotating rotors for Urban Air Mobility
MSc Thesis

35. 35
Today’s agenda…

36. 36
Today’s agenda…
Co-rotating rotor

37. 37
Today’s agenda…
Co-rotating rotor Literature Study
&
Research Questions

38. 38
Today’s agenda…
Co-rotating rotor Literature Study
&
Research Questions
Software & Setup

39. 39
Today’s agenda…
Co-rotating rotor Literature Study
&
Research Questions
Software & Setup Results

40. 40
Today’s agenda…
Co-rotating rotor Literature Study
&
Research Questions
Software & Setup Results
Conclusions
&
Recommendations

41. 41
Basics of Co-rotating rotor

42. 42
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor

43. 43
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
𝑉∞

44. 44
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
𝑉∞

45. 45
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
𝑉∞

46. 46
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
𝑉∞

47. 47
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
Co-rotating rotor
𝑉∞

48. 48
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
Co-rotating rotor
𝑉∞

49. 49
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
Co-rotating rotor
𝑉∞

50. 50
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
Co-rotating rotor
𝑉∞

51. 51
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
Co-rotating rotor
𝑉∞

52. 52
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
Co-rotating rotor
𝑉∞

53. 53
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
Co-rotating rotor
𝑉∞

54. 54
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
Co-rotating rotor
𝑉∞

55. 55
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
Co-rotating rotor
𝑉∞

56. 56
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
• Blade Vortex Interaction (BVI)
1Image courtesy: E. Grande, Wind Energy group
1
Co-rotating rotor

57. 57
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
• Blade Vortex Interaction (BVI)
– Tip vortices shed from each rotor
1Image courtesy: E. Grande, Wind Energy group
1
Co-rotating rotor

58. 58
Basics of Co-rotating rotor
• Total thrust: Upper rotor + Lower rotor
• Streamtube of the rotor
– Thrust streamtube contracts more
• Upper rotor thrust > Lower rotor thrust
• Inflow effect: Mutual interaction of the two streamtubes
– Axial velocities compared to isolated rotor
– Upper rotor thrust
– Lower rotor thrust
• Blade Vortex Interaction (BVI)
– Tip vortices shed from each rotor
• Total noise: Upper rotor + Lower rotor
1Image courtesy: E. Grande, Wind Energy group
1
Co-rotating rotor

59. 59
Literature Review
and History

60. 60
Literature Review
• A brief history:
– First introduced – Mackaness 1909, in automotive industry
– NASA – 1974, 1976, etc
– Tail rotor of Apache AH-64 D (attack helicopter)
and History

61. 61
Literature Review
1. Ramasamy1 2015: axial separation thrust
• A brief history:
– First introduced – Mackaness 1909, in automotive industry
– NASA – 1974, 1976, etc
– Tail rotor of Apache AH-64 D (attack helicopter)
1: Manikandan Ramasamy: Hover Performance Measurements toward understanding aerodynamic interference in co-axial, tandem, and tilt rotors, UARC-NASA
and History

62. 62
Literature Review
1. Ramasamy1 2015: axial separation thrust
2. Mahendra2 2018: angular separation thrust , even more than contra-rotating rotors
2: Mahendra Bhagwat: Co-rotating and Counter-rotating coaxial rotor performance, US Army Aviation Development Directorate, CA 94035
• A brief history:
– First introduced – Mackaness 1909, in automotive industry
– NASA – 1974, 1976, etc
– Tail rotor of Apache AH-64 D (attack helicopter)
and History

63. 63
Literature Review
1. Ramasamy1 2015: axial separation thrust
2. Mahendra2 2018: angular separation thrust , even more than contra-rotating rotors
3. Whiteside3 2019: angular separation noise
3: Siena KS Whiteside: An Exploration of the Performance and Acoustic Characteristics of UAV-Scale Stacked Rotor Configurations, NASA LRC, VA 23681
• A brief history:
– First introduced – Mackaness 1909, in automotive industry
– NASA – 1974, 1976, etc
– Tail rotor of Apache AH-64 D (attack helicopter)
and History

64. 64
Research Questions

65. 65
• What are the flow phenomena taking place for a co-rotating rotor?
Research Questions

66. 66
• What are the flow phenomena taking place for a co-rotating rotor?
• What is the difference in computational and experimental results? Why?
Research Questions

67. 67
• What are the flow phenomena taking place for a co-rotating rotor?
• What is the difference in computational and experimental results? Why?
• Can the flow phenomena be utilized to increase thrust and decrease noise?
Research Questions

68. 68
• What are the flow phenomena taking place for a co-rotating rotor?
• What is the difference in computational and experimental results? Why?
• Can the flow phenomena be utilized to increase thrust and decrease noise?
• Which produces more noise for the same thrust: Co-rotating vs Single rotor?
Research Questions

69. 69
Software

70. 70
• Dassault Systèmes PowerFLOW – high-fidelity solver
Software

71. 71
• Dassault Systèmes PowerFLOW – high-fidelity solver
– LBM-VLES based
– LBM: Lattice Boltzmann Method
– VLES: Very Large Eddy Simulation
Software

72. 72
• Dassault Systèmes PowerFLOW – high-fidelity solver
– LBM-VLES based
– LBM: Lattice Boltzmann Method
– VLES: Very Large Eddy Simulation
• LBM – based on discretized Boltzmann equation
Software

73. 73
• Dassault Systèmes PowerFLOW – high-fidelity solver
– LBM-VLES based
– LBM: Lattice Boltzmann Method
– VLES: Very Large Eddy Simulation
• LBM – based on discretized Boltzmann equation
Software
Convective term
Collision
operator

74. 74
• Dassault Systèmes PowerFLOW – high-fidelity solver
– LBM-VLES based
– LBM: Lattice Boltzmann Method
– VLES: Very Large Eddy Simulation
• LBM – based on discretized Boltzmann equation
– mesoscopic method
Software
Convective term
Collision
operator
f – particle distribution function

75. 75
• Dassault Systèmes PowerFLOW – high-fidelity solver
– LBM-VLES based
– LBM: Lattice Boltzmann Method
– VLES: Very Large Eddy Simulation
• LBM – based on discretized Boltzmann equation
– mesoscopic method
• VLES – Turbulence modelling for high-Re flows
– RNG1 k-𝜀 turbulence model
– Law of the wall – near boundary
Software
Convective term
Collision
operator
f – particle distribution function
1RNG: Renormalization Group

76. 76
PowerFLOW Setup

77. 77
PowerFLOW Setup
• Cubic simulation volume

78. 78
PowerFLOW Setup
• Cubic simulation volume Higher resolution

79. 79
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
Higher resolution

80. 80
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
Higher resolution

81. 81
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
• Highest resolution near the blade Highest resolution

82. 82
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
• Highest resolution near the blade
• APC 18x5.5 MR – single 2-bladed

83. 83
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
• Highest resolution near the blade
• APC 18x5.5 MR – single 2-bladed
• Co-rotating rotor 2×2-bladed

84. 84
PowerFLOW Setup
• Cubic simulation volume
• Variable Resolution (VR) regions used
• Highest resolution near the blade
• APC 18x5.5 MR – single 2-bladed
• Co-rotating rotor 2×2-bladed
• n = 50 rps
• Hover cases

85. 85
Rotor Configurations

86. 86
Rotor Configurations
1. Single rotor – isolated baseline rotor
1

87. 87
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
1
2

88. 88
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
3. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 12°
1
2
3

89. 89
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
3. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 12°
4. Single rotor
– at same thrust as co-rotating rotor
1
2
3
4

90. 90
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
3. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 12°
4. Single rotor
– at same thrust as co-rotating rotor
1
2
3
4

91. 91
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
3. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 12°
4. Single rotor
– at same thrust as co-rotating rotor
1
2
3
4

92. 92
Rotor Configurations
1. Single rotor – isolated baseline rotor
2. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 84°
3. Co-rotating rotor
– axial – 1.1 inch (2.79 cm)
– angular - 12°
4. Single rotor
– at same thrust as co-rotating rotor
1
2
3
4

93. 93
Aeroacoustic Setup
• PowerFLOW

94. 94
Aeroacoustic Setup
• PowerFLOW
– Ffowcs-Williams and Hawkings (FWH) methodology for
far-field aeroacoustic post-processing

95. 95
Aeroacoustic Setup
• PowerFLOW
– Ffowcs-Williams and Hawkings (FWH) methodology for
far-field aeroacoustic post-processing
– Sampling of pressure fluctuations on spherical surfaces

96. 96
Aeroacoustic Setup
• PowerFLOW
– Ffowcs-Williams and Hawkings (FWH) methodology for
far-field aeroacoustic post-processing
– Sampling of pressure fluctuations on spherical surfaces
– Sampling frequency – 40000 Hz

97. 97
Flow Physics Investigation
• 84° angular separation
Configuration 2

98. 98
Flow Physics Investigation
• 84° angular separation
Configuration 2

99. 99
Flow Physics Investigation
• 84° angular separation
1Experiment - Thrust and Acoustic Performance of small-scale, co-axial, co-rotating rotors in hover, Charles E. Tinney, AIAA Journal, 2019
Configuration 2
PowerFLOW (N) Experiment1 (N) Difference (N) Difference (%)
12.22 13.94 1.72 12.34

100. 100
Flow Physics Investigation
• 84° angular separation
– difference with experiments
1Experiment - Thrust and Acoustic Performance of small-scale, co-axial, co-rotating rotors in hover, Charles E. Tinney, AIAA Journal, 2019
Configuration 2
PowerFLOW (N) Experiment1 (N) Difference (N) Difference (%)
12.22 13.94 1.72 12.34

101. 101
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
1Experiment - Thrust and Acoustic Performance of small-scale, co-axial, co-rotating rotors in hover, Charles E. Tinney, AIAA Journal, 2019
Configuration 2
PowerFLOW (N) Experiment1 (N) Difference (N) Difference (%)
12.22 13.94 1.72 12.34
Baseline rotor (N) Upper rotor 84o (N) Lower rotor 84o (N)
8.23 7.22 5

102. 102
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
1Experiment - Thrust and Acoustic Performance of small-scale, co-axial, co-rotating rotors in hover, Charles E. Tinney, AIAA Journal, 2019
Configuration 2
PowerFLOW (N) Experiment1 (N) Difference (N) Difference (%)
12.22 13.94 1.72 12.34
Baseline rotor (N) Upper rotor 84o (N) Lower rotor 84o (N)
8.23 7.22 5

103. 103
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

104. 104
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

105. 105
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

106. 106
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

107. 107
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

108. 108
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
∅: Inflow angle
𝛼: Angle of attack
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

109. 109
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

110. 110
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

111. 111
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2
𝐶 𝑇 =
𝑇ℎ𝑟𝑢𝑠𝑡
𝜌𝑛2 𝐷4

112. 112
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2

113. 113
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
Configuration 2

114. 114
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with baseline rotor
– lower rotor < upper rotor < baseline rotor
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
– Blade Vortex Interaction (BVI)
• tip vortices interaction with rotor blades
Configuration 2

115. 115
Flow Physics Investigation
Configuration 2

116. 116
Flow Physics Investigation
Lower rotor Upper rotor
Configuration 2

117. 117
Flow Physics Investigation
Lower rotor
Configuration 2

118. 118
Flow Physics Investigation
Configuration 2
Co-rotating 84° Baseline rotor

119. 119
Flow Physics Investigation
Configuration 2
Co-rotating 84° Baseline rotor

120. 120
Flow Physics Investigation
Configuration 2
Co-rotating 84° Baseline rotor

121. 121
Flow Physics Investigation
Configuration 2

122. 122
Flow Physics Investigation
Configuration 2

123. 123
Flow Physics Investigation
• 84° angular separation
– difference with experiments
• Comparison with 2-bladed rotor
– lower rotor < upper rotor < 2-bladed
• Flow Phenomena
– Inflow Effect
• mutual interaction of streamtubes
– Blade Vortex Interaction (BVI)
• tip vortices interaction with rotor blades
Configuration 2
Inflow effect BVI

124. 124
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3

125. 125
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3

126. 126
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34

127. 127
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34

128. 128
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34

129. 129
• Angular separation from 84° to 12°
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34

130. 130
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34

131. 131
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34
Baseline rotor (N) Upper rotor 12° (N) Lower rotor 12° (N)
8.23 8.96 2.74

132. 132
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34
Baseline rotor (N) Upper rotor 12° (N) Lower rotor 12° (N)
8.23 8.96 2.74

133. 133
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
Configuration 3
Angular PowerFLOW (N) Experiment (N) Difference (N) Difference (%)
12° 11.7 13.34 1.64 12.29
84° 12.22 13.94 1.72 12.34
Baseline rotor (N) Upper rotor 12° (N) Lower rotor 12° (N)
8.23 8.96 2.74

134. 134
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
1AMO Smith, High Lift Aerodynamics, Journal of Aircraft, 1975
1
Configuration 3
Baseline rotor (N) Upper rotor 12° (N) Lower rotor 12° (N)
8.23 8.96 2.74

135. 135
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
Configuration 3

136. 136
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
Configuration 3

137. 137
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
Configuration 3

138. 138
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
Flow Physics Investigation
Configuration 3

139. 139
• Angular separation from 84° to 12°
– Upper rotor thrust
– Lower rotor thrust
• Flow Phenomena
– Circulation effect
– Inflow effect
– BVI effect
Flow Physics Investigation
Configuration 3

140. 140
Coupled System of Rotor
Configuration 3

141. 141
Coupled System of Rotor
84o → 12o azimuthal
variation
Configuration 3

142. 142
Coupled System of Rotor
84o → 12o azimuthal
variation
Circulation effect
becomes important 1
Configuration 3

143. 143
Coupled System of Rotor
Upper rotor
thrust increases
84o → 12o azimuthal
variation
Circulation effect
becomes important 1
2
Configuration 3

144. 144
Coupled System of Rotor
Upper rotor
thrust increases
Axial velocity on lower
rotor increases
Circulation effect
becomes important 1
2
3
Configuration 3

145. 145
Coupled System of Rotor
Upper rotor
thrust increases
Axial velocity on lower
rotor increases
Lower rotor
thrust decreases
Circulation effect
becomes important 1
2
3
4
Configuration 3

146. 146
Coupled System of Rotor
Upper rotor
thrust increases
Axial velocity on lower
rotor increases
Lower rotor
thrust decreases
Axial velocity on upper
rotor decreases
Circulation effect
becomes important 1
2
3
4
5
Configuration 3

147. 147
Coupled System of Rotor
Upper rotor
thrust increases
Axial velocity on lower
rotor increases
Lower rotor
thrust decreases
Axial velocity on upper
rotor decreases
Circulation effect
becomes important 1
2
3
4
5
Converged state!
Configuration 3

148. 148
Flow Phenomena

149. 149
Flow Phenomena
• Inflow Effect

150. 150
Flow Phenomena
• Inflow Effect
• Blade Vortex Interaction (BVI)

151. 151
Flow Phenomena
• Inflow Effect
• Blade Vortex Interaction (BVI)
• Circulation Effect
1
1AMO Smith, High Lift Aerodynamics, Journal of Aircraft, 1975

152. 152
Flow Phenomena
• Inflow Effect
• Blade Vortex Interaction (BVI)
• Circulation Effect

153. 153
Flow Phenomena
• Inflow Effect
• Blade Vortex Interaction (BVI)
• Circulation Effect
Only for low angular separation!!!

154. 154
Flow Phenomena
• Inflow Effect
• Blade Vortex Interaction (BVI)
• Circulation Effect
Only for low angular separation!!!
Has the potential to increase the co-rotating rotor performance!!!

155. 155
Noise Investigation
• probes - 3×rotor diameter from rotor axis
Configuration 3

156. 156
Noise Investigation
• probes - 3×rotor diameter from rotor axis
Configuration 3

157. 157
Noise Investigation
• probes - 3×rotor diameter from rotor axis
Configuration 3

158. 158
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
Configuration 3

159. 159
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
Configuration 3

160. 160
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
Configuration 3

161. 161
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
Configuration 3

162. 162
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
Configuration 3

163. 163
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
Configuration 3

164. 164
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
12°84°
Configuration 3

165. 165
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
– destructive interference
12°84°
Configuration 3

166. 166
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
– destructive interference
12°84°
Configuration 3

167. 167
Noise Investigation
• probes - 3×rotor diameter from rotor axis
• Noise spectra
– 12° vs 84°
• Overall SPL (90-4000 Hz)
• Pressure fluctuations
– destructive interference
12°84°
Configuration 3

168. 168
Noise Comparison
Configuration 4
• Two comparisons made
a) Co-rotating rotor 84o vs single rotor (having same thrust as 84o rotor)
b) Co-rotating rotor 12o vs single rotor (having same thrust as 12o rotor)
Angular (°) Co-rotating rotor (N) Single rotor (N)
a) 84 12.22 12.24
b) 12 11.7 11.8

169. 169
Noise Comparison
Configuration 4
• Two comparisons made
a) Co-rotating rotor 84o vs single rotor (having same thrust as 84o rotor)
b) Co-rotating rotor 12o vs single rotor (having same thrust as 12o rotor)
Angular (°) Co-rotating rotor (N) Single rotor (N)
a) 84 12.22 12.24
b) 12 11.7 11.8
a)

170. 170
Noise Comparison
Configuration 4
• Two comparisons made
a) Co-rotating rotor 84o vs single rotor (having same thrust as 84o rotor)
b) Co-rotating rotor 12o vs single rotor (having same thrust as 12o rotor)
Angular (°) Co-rotating rotor (N) Single rotor (N)
a) 84 12.22 12.24
b) 12 11.7 11.8
a) b)

171. 171
Conclusions

172. 172
Conclusions
• Flow Phenomena
– Inflow effect
– Blade Vortex Interaction (BVI)
– Circulation effect

173. 173
Conclusions
• Flow Phenomena
– Inflow effect
– Blade Vortex Interaction (BVI)
– Circulation effect
• Difference with experiments
– Some aspects of experimental setup unable to be captured

174. 174
Conclusions
• Flow Phenomena
– Inflow effect
– Blade Vortex Interaction (BVI)
– Circulation effect
• Difference with experiments
– Some aspects of experimental setup unable to be captured
• Circulation effect can be utilized to increase thrust

175. 175
Conclusions
• Flow Phenomena
– Inflow effect
– Blade Vortex Interaction (BVI)
– Circulation effect
• Difference with experiments
– Some aspects of experimental setup unable to be captured
• Circulation effect can be utilized to increase thrust
• Application-based goal:
– Higher thrust: 12o co-rotating configuration
– Lower noise: 84o co-rotating configuration

176. 176
Recommendations

177. 177
Recommendations
• Further investigations needed on differences with experiments

178. 178
Recommendations
• Further investigations needed on differences with experiments
• Differential collective pitch and differential radius studies should be performed

179. 179
Recommendations
• Further investigations needed on differences with experiments
• Differential collective pitch and differential radius studies should be performed
• Investigations should be made with angular separation higher than 90o

180. 180
Recommendations
• Further investigations needed on differences with experiments
• Differential collective pitch and differential radius studies should be performed
• Investigations should be made with angular separation higher than 90o
• Lower rotor blade design should be optimized due to different inflow conditions

181. 181
Thank You

182. 182
Differential Collective Pitch
Configuration 3

183. 183
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
Configuration 3

184. 184
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
Configuration 3

185. 185
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
Configuration 3

186. 186
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Configuration 3

187. 187
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Configuration 3

188. 188
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Configuration 3

189. 189
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Configuration 3

190. 190
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Configuration 3

191. 191
Differential Collective Pitch
• Increase collective pitch angle of lower rotor
– 2 opposing effects → circulation and inflow
– upper rotor thrust should remain constant!
– Total thrust
Double thrust within same rotor space!!!
Configuration 3

192. 192
• Axial Velocity [-] = v/n.D