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Numerical Prediction of Aerodynamic
Characteristics of a Hummingbird
Vishnupriya . R, Sharpunisha. N, Raju Govindharajan & G. Chandra Bose
Dept. of Aeronautical Engineering P. B. College of Engineering,
E-mail : [email protected], [email protected], [email protected] & [email protected]
Abstract – Hummingbirds are widely thought to employ
aerodynamic mechanisms similar to aircrafts. Also
hummingbird wings are capable of operating in more
viscous regimes. The present analysis is to study the
aerodynamics of a hummingbird using computational
simulation. The wake patterns around the bird is
simulated which significantly enables to visualize the
pressure distribution and flow patterns. The lift and drag
forces were measured from which high values of lift: drag
ratio at low angles of attack is obtained. The above result
concludes that wings of hummingbird are good at
producing more lift.
assumed that lift was generated equally during
the
phases
of the wing beat cycle. When hummingbird
aerodynamics employs the use of down stroke to hover,
about a quarter of their weight is supported by it and the
upstroke supports the rest. Such extensive research
performed on determining the mechanism involved in
hummingbird aerodynamics and hence it has the power
to influence the technology employed in future flying
machines. In fact, the mechanisms of helicopters have
been influenced by the study of hummingbird
aerodynamics.
Keywords – aerodynamics, angle of attack, lift coefficient,
drag coefficient.
Zongxian Liang et al [3] numerically simulated the
hummingbird wings model undergoing hovering flight.
3D wake structures and its associated aerodynamic
performance were visualised. It was found that the
amount of lift produced during down stroke is about 3
times of that produced in upstroke and also two parallel
vortex rings were formed at the end of the upstrokes.
I.
INTRODUCTION
Hummingbirds have been studied for their unusual
display of aerodynamics. It weighs one-fourteenth of an
ounce and, like helicopters, can fly forward, backward,
sideways and can hover in mid-air. They are among the
smallest of birds, most species measuring in the 7.5–
13 cm (3–5 inch) range. This bird‟s wings appear to be
backwards (i.e.) the leading edge of its wing is behind
the feathers. This is because of the wing movement
horizontally back and forth during hovering. The
Reynolds number for a hummingbird hover flight ranges
from 103 to 104 and flapping frequency is about 41 Hz
(i.e.) they can hover in mid-air by rapidly flapping their
wings 12–80 times per second. And also they are
capable of greater forward velocities, exceeding 30 ms-1.
Hummingbird flight has been studied intensively from
an aerodynamic perspective. There are many forces of
interest, from the tilt of the body to the stroke of the
wings. Everything combines together to form an
inspiring hummingbird flight. They have higher angle of
attack at mid down stroke than during mid upstroke. In
both halves of the wing stroke, the feathers point
downward at an angle to produce lift. Earlier studies had
[3]
Douglas L. Altshuler et al
compared the
aerodynamic forces of revolving hummingbird wings
and wing models.
The lift an drag forces were
measured and it was observed that the lift: drag ratios of
real wings were substantially higher than those of wing
models.
Bret W. Tobalske et al [4] studied the aerodynamics
of hummingbird flight using Digital Particle Image
Velocimetry.
DPIV analysis suggested that an
extended wing upstroke during forward flight produces
lift and negative thrust and circulation during down
stroke is sufficient to support body weight.
Donald R. Powers et al [3] determined that the
airflow over hummingbird wings is dominated by a
stable, attached leading edge vortex. Using PIV
technique the 2D flow field around the wing of a
hummingbird is captured from which the vorticity over
the dorsal surface is visualised. And hence the lift
ISSN : 2319 – 3182, Volume-2, Issue-3, 2013
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International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)
production decreases until the energy of the leading
edge vortices is re-captured.
II. METHODOLOGY
A. Physical Model
The 3D cad model used for computational analysis
is modelled using CATIA and the same is shown in
figure 1. On comparing the various data‟s of a
hummingbird, the length and wing span is taken as 48
mm and 28 mm respectively.
Fig. 2(b) : Computational Domain
C. Boundary conditions
The flow at the inlet domain is set to subsonic with
the following solver setup
FLOW (time)
Fig. 1 : Hummingbird Model
B. Numerical Approach
The computational grid used for this analysis is
shown in figure 2(a). The surface mesh with required
mesh refinements is created with the total surface
elements of 134754. An unstructured volume mesh is
created with a growth rate of 1.2. The numerical
analysis is carried out using RANS based CFD solver.
For the present analysis 3D incompressible equations
are solved with air as the working fluid. The standard kε model is activated in order to capture the turbulent
flow properties over the bird.
STEADY
FLOW (density)
INCOMPRESSIBLE
EQUATIONS
CONTINUITY,
MOMENTUM AND KEPSILON
MATERIAL
TYPE
LUID(ATMOSPHERIC
AIR)
FLOW
INITIALIZATION
11.11 m/s
REFERENCE
PRESSURE
1 atm
The exit of the domain is set to „pressure outlet‟
boundary condition. The entire bird model is set to „noslip wall‟ boundary condition with standard wall
functions
III. RESULTS AND DISCUSSION
Numerical simulation of external flow field around
the bird is predicted. The analysis is carried out for
various angles of attack and its corresponding static
pressure distribution, wake patterns and turbulence
intensities are captured and the same is shown in figure
3(a).
Fig. 2(a) : Refined Volume Mesh Around The Bird
Fig. 3(a) : Static Pressure Distribution Around The Bird
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International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)
The above figure displays the static pressure rise at
the ventral portion of the body as a result of abrupt
reduction in flow velocity.
0.32
0.3
The figure 3(b) displays the static pressure
distribution over the wings for 4 degree angle of attack
.The maximum pressure at the ventral side and low
pressure at the dorsal portion are captured. This
significantly increases the lift.
CD
0.28
0.26
0.24
0.22
0.2
-5
0
5
10
α ( degree )
Fig. 3(e): CD VS. Alpha Curve
From the above plots it is concluded that the
maximum lift is generated for 4 degree angle of attack
and the drag increases gradually. Further, when the
angle of attack is increased, stall occurs.
Fig. 3(b) : Static Pressure Distribution over the wings
for 4 degree angle of attack
Figure 3(c) displays the static pressure distribution over
the cross section of the wing profile at 4 degree angle of
attack, for which maximum lift is obtained. Maximum
pressure is generated at leading edge of the cross
section.
IV. CONCLUSION
The 3D numerical simulation of aerodynamic
characteristics of a hummingbird is carried out . The
flow physics around the bird is predicted from which it
is observed that high values of lift is obtained at low
angle of attack. The trend of drag vs. Angle of attack
curve shows increment in drag as angle of attack
increases. This is because the projected area of the bird
increases as the flow angle increases. Thus the
computational methodology very well predicts the flow
physics of a hummingbird.
Fig. 3(c) : Static Pressure Distribution Across The Wing
Profile
REFERENCES
The aerodynamic forces are calculated from which
the lift to drag ratio is obtained. The maximum lift and
stall angle of the bird is determined from the plots
shown in figure 3(d) and 3(e). The results are discussed
below.
[1]
Zongxian
Liang1
and
Haibo
2
Dong ”COMPUTATIONAL ANALYSIS OF
HVERING
HUMMINGBIRD
FLIGHT
“Department of Mechanical & Materials
Engineering, Wright State University, Dayton.
[2]
Douglas R. Warrick1,*, Bret W. Tobalske2 and
Donald R. Powers 3 “ LIFT PRODUCTION IN
HOVERING HUMMINGBIRD FLIGHT “
Department of Zoology, Oregon State University,
3029 Cordley Hall, Corvallis, OR 97331,
USA2Field Research Station at Fort Missoula,
Division of Biological Sciences, University of
Montana, Missoula, 3Biology Department,
George Fox University, 414 N. Meridian Street,
Newberg, , USA.
[3]
Douglas R. Warrick 1and Bret W. Tobalske2
“THE AERODYNAMICS OFHUMMINGBIRD
0.4
CL
0.38
0.36
0.34
0.32
0.3
-4 -3 -2 -1
0 1 2
α (degree)
3
4
5
6
Fig. 3(d) : CL VS. Alpha Curve
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International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)
[4]
FLIGHT “Oregon State University, Corvallis
Oregon 97331 and University of Portland,
Portland
NOMENCLATURE
Douglas L. Altshuler', Robert Dudley 2and
Charles P. Ellington 3
“AERODYNAMIC
FORCES OF REVOLVING HUMMINGBIRD
WINGS “ University of Texas at Austin, Austin,
Texas, U.S.A. Smithsonian Tropical Research
Institute, Balboa, Republic of Panama
CD
Force coefficient in x direction
α
Angle of attack (degree)
Re
Reynolds number
CL
Force coefficient in y direction

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