Animal - Section B - Locomotion 2 (Birds) Flashcards
Flying is similar to swimming except that birds cannot generate _____ ____
passive lift (buoyancy)
How does an aerofoil work?
In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing. Because the upper flow is faster, then, from Bernoulli’s equation, the pressure is lower. The difference in pressure across the airfoil produces the lift.
_______ movement of the wing pushes the body ______ generating thrust
Downward movement of the wing pushes the body forwards generating thrust
The shape wing aerofoil varies across the wing, why?
??????
The shape of the wing aerofoil is _____ pronounced towards the ___ because you dont want all of the lift out at the ___ of the wings as it will create alot of pressure/torque on keeping them in place, hence why the wider part of the foil is ______ to the body so the chest _______ can control them better.
- Less
- Tip
- End
- Closer
- Muscles
Name A___ is located towards the ____ of the wing and the T___ W___S__ are located towards the ___
- Alula (leading edge wing flap)
- Terminal wing slots
CL =
&
CD =
Both increase the wing angle of attack
The _____ creates a slot at the leading edge of the wing that _______ the airflow over the upper surface of the wing and reduces risk of stalling
(Like the flaps that project on a aeroplane wing upon take off during the high angle take off)
-Alula
What is going on here?
As airspeed increases
form drag increases
enduced drag reduces
High aspect ratio wings like the shearwater give you less of what and more of what?
- Decrease in induced drag
- Increase in profile drag and a greater bending stress.
(Low aspect ratio birds such as pheasents have low speed manouverability, high roll rate but greater induced drag)
Wing tip primary feathers _____ induced drag and create lots of ____ ____ rather than large ones
A. Dissapate
B. Small eddies
An engineering solution to reducing airflow at the end of the wing and reduce drag is…
Blended winglets. They are upturned wings on planes which significantly decreases the vortex size and amount of drag created by the plane. Creates a huge amount of turbulence which can cause a smaller plane to crash if it hits the ‘rough patch’ of air.
Why do birds fly in V formation?
(migrating ibises)
- One leading bird
- Trailing birds positioned in V formation take advantage of vortex-induced upwash created by the leading bird which saves energy.
- Approx 1m to the side and 1m behind the leading bird
- You can alter the geometry of the wing for different amounts of lift
- Here you can see a plane coming into land
(Trailing edge flaps out for larger surface area for more lift as when the plane slows down it decreases the chance of a stall)
(When the plane is at cruising altitude, the plane retracts these flaps in order to reduce the over all surface of the wing in order to reduce drag)
Wing form of plane similar to a birds when landing, flying straight and taking off.
Feathers
Primary feathers provide a smooth surface but are
-light
&
-compliant
(the surface is not rigid)
-acts like whale blubber in the water = less turbulence
Vertical take off and hovering
Hummingbirds ______ their wings to achieve both ____ and ____
A.Rotate
B.Lift
C.Thrust
They have to bring their wings forward to generate lift in one direction and push down to generate thrust and then roate the wings upside down in order to do that backwards.
What is induced drag?
Induced drag (Di)
Airflow around the wing from the lower area of high pressure to the upper low pressure area produces large eddies that causes a loss of lift
What is form drag aka profile drag?
Form Drag aka Profile Drag (Dp)
- Drag acting on the wings and body including friction drag
- The displacment of air
- The creation of pressure gradients in the air
- the creation of eddies and vortices
The alula is particularly important for ___ speed manouveres and when the angle of attack _________ when a bird comes into land and they are trying to control small adjustment movements. Air movement must be _________ in order to create more ___ ____ and reduce the risk of a _____.
- low speed manouveres
- increases
- increased
- air flow
- stall
Leading edge slots such as the alula and those of ariplanes can increase the coefficient of lift by up to __% and increase the stall angle from typical __ to __ degree.
- 60%
- 15 - 25 degree
What is the stall angle?
A stall is a condition in aerodynamics and aviation wherein the angle of attack increases beyond a certain point such that lift begins to decrease. Theangle at which this occurs is called the critical angleof attack.
What are swing wings?
- Different wing types for different velocitys
- Sweep wings back to reduce drag profile to go faster with less effort
- Gannet sweeping wings back to gain more velocity when diving into the water
- Ability to alter geomotry of wings to create different amounts of lift
Explain convergent evolution in different types of birds occupying the same ecological niche
Southern hemisphere aquatic birds vs Northern hemisphere aquatic birds
(penguins vs auks)
Penguins in Southern Hemisphere only
Aucks & Puffins in Northern Hemisphere only
BUT
When you look at the design of the animals they are virtually exactly the same in terms of their body plan, shape and shape of their flippers despite the fact that they are not related in any sort of way. So adopting that ecological niche has resulted in covergent evolution between those two different types of birds in that same environment.
How do bird feathers retain heat?
- Very efficient for thermoreguation as they trap air very effectively and its the air that provides insulation to prevent the bird from getting cold
- As a warm blooded animal they generate lots of heat which is retained by sufficient insulation
- Primary feathers also provides a smooth surface and compliant surface (less turbulence from a more flexible surface)
- A soft feathered surface moves/flexes as the bird is flying through the air and it dampens out changes in pressure in the boundary layer of air acting just like the dimples on a golf ball reducing drag.
