It is about the effect of Leading Edge Tubercles on flapping wing apparatus in Energy Extraction Mode.

2. Total slides : 35
EFFECT OF TUBERCLES ON A FLAPPING WING
IN ENERGY EXTRACTION MODE
STUDENT

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SEQUENCE
Scope
Minimum passing requirement
Literature review
Methodology
Validation
Results
Conclusion
Challenges
Future Recommendations
References

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SCOPE
CFD analysis of a flapping hydrofoil with LE
Tubercles to determine the power coefficients.
Comparison of Fluid flow and Power
Coefficients between LE Tubercles and Baseline
Model
Studying the flow dynamics of tubercles and
their effect on flapping wings.

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MINIMUM PASSING REQUIREMENT
Effect of LE Tubercles on Energy Extraction from active
flapping wing system
Best case of LE Tubercles that is most efficient for
Energy Extraction from flapping wing

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LITERATURE REVIEW
Tubercles
These are the bumps or perturbations present on the
leading edge of humpback whales.
The job of the tubercle is to generate vortices to
maintain lift and avoid stalling at steep angles of attack.
Tubercles on Humpback whale’s flipper
Wave like tubercles

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LITERATURE REVIEW
Energy Extraction from Flapping Wings
Types of flapping foil Energy Harvesters
 Fully activated system
 Semi activated system
 Fully passive system
Active System Modelling
 Heaving Motion θ(t)
h(t) = H0sin(γ t + φ)
 Pitching Motion h(t)
θ(t) = θ0sin(γ t)
Source: Kinsey and Dumas 2008

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LITERATURE REVIEW
Feathering Effect
A feathering state is reached when the heave-induced
angle of attack equals the pitching angle. At this state, the
oscillating wing generates neither thrust nor drag.
Source: Young et al 2014
Power Extraction
 Heaving contribution
Py(t) = Y (t) Vy(t)
 Pitching contribution
Pθ(t) = M(t) Ω(t)

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LITERATURE REVIEW
Power Efficiency
The power-extraction efficiency η is the ratio of the mean
total power extracted P to the total power available Pa in
the oncoming flow passing through the swept area (the
“flow window”).
Source: Thomas Kinsey 2011

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LITERATURE REVIEW
Comparative Literature on power extraction from flapping
foil
Reference Year Geometry Activation Re Cpmax ηmax
Jones et al. 2003 NACA0014 Active 1.0*106 Nil 0.12
Kinsey and
Dumas 2008
NACA0015
Active 1100 1.13 0.34
Platzer et al. 2009 NACA0014 Active 20000 1.44 0.54
Young et al. 2010 NACA0012 Passive 1100 0.79 0.30
Bryant et al. 2012 Flat plate Active 5000 0.7 0.27
Kinsey and
Dumas
2012 NACA0015 Active 5.0*105 1.60 0.63
Young et al. 2013 NACA0012 Passive
1100 and
1.1*106 1.10 0.41
Zhu and
Peng
2009
12% thick
Joukowski
Semi
passive
1000 0.31 0.27

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METHODOLOGY
Literature
Review
CFD Analysis
on Tubercled
Models
Comparison of
results
CAD Models
with LE
Tubercles
CFD Analysis
on Baseline
Model
Selection of
Research paper
for Validation
Conclusion
Future
Recommendations

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VALIDATION
Geometry Modelling
 NACA0015 will be used for validation purposes.
CAD Model of NACA0015

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VALIDATION
Domain Modelling
Isometric views of Inner and Complete domain

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VALIDATION
Grid Generation

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VALIDATION
Solution Approach
1. Dynamic Meshing
This method is used to simulate problems with the boundary
motion. The user can define body motion in dynamic mesh
method using the UDF. Negative cell volumes during the 3D case
is a major problem while using this method.
2. Sliding Mesh
This method is used to simulate unsteady problems that are
periodic in nature. Rotational velocity is mainly used in this
method which can be given with the help of UDF or expressions.

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VALIDATION
 User Defined Function
Source: Kinsey et al 2013

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VALIDATION
Boundary Conditions
Complete Boundary Conditions
Inlet Boundary Condition

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VALIDATION
Cell zone Conditions

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VALIDATION
Fluid Properties and Reference Values
• Air was taken as fluid.
• Following reference
values were taken to get
accurate non-dimensional
parameters.

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VALIDATION
Initialization and Calculation

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VALIDATION
Grid Independence
Mesh Size Cp
1 1.50 million 0.72
2 2.35 million 0.73
3 3.18 million 0.736
Case 1 Case 2 Case 3
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
1 1.5 2 2.5 3 3.5
Cp
Mesh Elements (millions)
Mesh Independence

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VALIDATION
Time step Independence
Time Step size (s) Cp
0.01 0.7306
0.015 0.7304
0.02 0.7293
0.01 0.015
0.02
0.725
0.727
0.729
0.731
0.733
0.735
0.007 0.012 0.017 0.022
Cp
Time step(s)
Time Independence

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VALIDATION
Selection of Turbulence Model
Turbulence Model Cp
SST-k omega 0.73
Spalart Allmaras 0.698

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VALIDATION
Comparison with Kinsey’s 3D Case
CPY CPθ CP η (%)
Best Case 0.9935 -0.263 0.730 28.6
Kinsey 1.026 -0.251 0.775 30.42
Error 0.0267 -0.012 0.045 1.82
Error (%) 2.53 4.78 5.80 5.92

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RESULTS
Geometry Modelling with LE Tubercles
For tubercles, there are two basic parameters:
 Amplitude in terms of percentage of chord
 Wavelength in terms of percentage of chord
Six different cases were designed with the help of CATIA software.
Cases Amplitude A (% of
chord)
Wavelength λ (% of chord)
1 2 5
2 4 10
3 6 15
4 8 20
5 10 25
6 12 50

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RESULTS
Tubercled Geometries
Top view of A2 λ05 Case
Top view of A10 λ25 Case
Top view of A6 λ15 Case
Top view of A4 λ10 Case
Top view of A12 λ50 Case
Top view of A8 λ20 Case

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RESULTS
Coefficient of Lift

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RESULTS
Coefficient of Moment

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RESULTS
Coefficient of Heaving Power

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RESULTS
Coefficient of Pitching Power

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RESULTS
Coefficient of Power

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RESULTS
Comparison of Cycle Averaged Power and Efficiency
Cases CPY CPθ CP η (%)
Baseline NACA0015 0.9935 -0.263 0.73 28.6
Tubercles A2 λ05 0.8973 -0.207 0.69 27.05
Tubercles A4 λ10 0.8972 -0.202 0.6956 27.27
Tubercles A6 λ15 0.908 -0.201 0.70 27.45
Tubercles A8 λ 20 0.903 -0.208 0.695 27.25
Tubercles A10 λ 25 0.9007 -0.214 0.687 26.94
Tubercles A12 λ50 0.919 -0.234 0.685 26.86

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RESULTS
Best Case
Case 3
CPY=0.908
η=27.45
CP=0.7
CPθ=-0.201

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RESULTS
Animation of Baseline NACA 0015

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RESULTS
Animation of A6 λ15 Case

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CONCLUSION
 The usage of LE Tubercles in any combination of amplitude and
wavelength showed that they did not increase the power production
rather they decreased the efficiency of the system.
 LE tubercles did help in mitigating the reduction of power due to the
pitching motion. Less power was lost due to the pitching motion due
to the LE tubercles.
 The flow pattern for all the cases is almost same except that lower
wavelengths showed smaller vortices at higher angle of attacks while
larger wavelengths showed larger vortices.
 Wavelengths in the range of 5 to 25 showed similar pattern of lift
reduction while wavelength of 50 did not reduce lift to that extent,
mainly because of stronger vortices present at steep angle of
attacks.

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CHALLENGES
High Processing Power
3D Transient simulations take a lot of time and processing power so,
high processing power PCs are required.
Electric Power
Simulations span over days sometimes so, constant supply of
electricity is very necessary for smooth work.

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FUTURE RECOMMENDATIONS
 Effect of tubercles on flapping wing in energy extraction mode can be
done at lower Reynolds number even though at lower Re, there is
less efficiency, but effect of LE tubercles can be observed.
 LE tubercles could be installed at tapered wings since in real life
whales have tapered fins so, their effect at tapered wings should be
studied.
 These LE tubercles could be fabricated to see their effects in real
time to get a better understanding of the flow physics.

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REFERENCES
 Jones KD, Lindsey K, Platzer MF. An investigation of the fluid-structure interaction in an
oscillating-wing micro-hydropower generator. In: Fluid– structure interaction II. Wessex Institute of
Technology Press, Southampton, UK; 2003. p. 73–82.
 Kinsey T, Dumas G. Parametric study of an oscillating airfoil in a powerextraction regime. AIAA J
2008;46(6):1318–1330, http://dx.doi.org/10.2514/ 1.26253.
 Platzer MF, Young J, Lai JCS. Flapping-wing technology: the potential for air vehicle propulsion
and airborne power generation. In: 26th International congress of the aeronautical sciences
(ICAS), Anchorage, Alaska, 14–19 September 2008.
 Young J, Ashraf MA, Lai JCS, Platzer MF. Numerical simulation of flow-driven flapping-wing
turbines for wind and water power generation. In: 17th Australasian fluid mechanics conference,
Auckland, New Zealand, 5–9 December 2010.
 Kinsey T, Dumas G. Computational fluid dynamics analysis of a hydrokinetic turbine based on
oscillating hydrofoils. J Fluids Eng 2012;134(2):021104- 1–021104-16,
http://dx.doi.org/10.1115/1.4005841.
 Young J, Ashraf MA, Lai JCS, Platzer MF. Numerical simulation of fully passive flapping foil power
generation. AIAA J 2013;51(11):2727–2739, http://dx.doi. org/10.2514/1.J052542.
 Bryant M, Shafer MW, Garcia E. Power and efficiency analysis of a flapping wing wind energy
harvester. In: Proceedings of SPIE, vol. 8341. International Society for Optics and Photonics,
Bellingham, Washington, p. 83410E-1–11, http://dx.doi.org/10.1117/12.915344, 2012.
 Zhu Q, Peng Z. Mode coupling and flow energy harvesting by a flapping foil. Phys Fluids
2009;21(3):033601-1–033601-10, http://dx.doi.org/10.1063/ 1.3092484.

40. THANK YOU

41. QUESTIONS

42. QUESTIONS