Comparative Anatomy and Physiology of Animals
Lecture 24 Aerial locomotion 20/01/21
Important forces
- Drag and gravity.
Physics of flying
- Air behaves like a fluid.
- The same principles of drag and lift talked about in aquatic locomotion apply to aerial
locomotion.
- The main differences relate to lower density of air relative to water, and the constant effect
of gravity.
-
- The movement of an animal through water is Reynolds number dependent, and it is also
dependent on the surface properties.
Lift to drag ratio
- Insects: lift/drag about 0.7-2.
- Birds: lift/drag about 7-20.
Wing properties
- Must account for lots of positive lift, lots of thrust, as little drag as possible (or as much
drag), and negative (like penguins swimming).
- And whatever the flying animal is trying to do at that point.
, -
- This is why wings are shaped so differently; they have got to do so many things.
Invertebrates
- Insect wings have margins which maintain the shape of the wing, allowing it to generate lift.
This is used in fields such as paragliding and windsurfing.
-
Insect flight muscles
- Muscles that power flight attach to the inside
of the thorax, not the wings themselves.
- Change in thorax shape forces the wings up
and down.
- Maximises power given the limited space
inside the exoskeleton.
- Muscles that attach to the wing are small
and only control wing orientation.
Hovering
- If your body is not moving, wings have to
move back and forth somehow.
Lecture 24 Aerial locomotion 20/01/21
Important forces
- Drag and gravity.
Physics of flying
- Air behaves like a fluid.
- The same principles of drag and lift talked about in aquatic locomotion apply to aerial
locomotion.
- The main differences relate to lower density of air relative to water, and the constant effect
of gravity.
-
- The movement of an animal through water is Reynolds number dependent, and it is also
dependent on the surface properties.
Lift to drag ratio
- Insects: lift/drag about 0.7-2.
- Birds: lift/drag about 7-20.
Wing properties
- Must account for lots of positive lift, lots of thrust, as little drag as possible (or as much
drag), and negative (like penguins swimming).
- And whatever the flying animal is trying to do at that point.
, -
- This is why wings are shaped so differently; they have got to do so many things.
Invertebrates
- Insect wings have margins which maintain the shape of the wing, allowing it to generate lift.
This is used in fields such as paragliding and windsurfing.
-
Insect flight muscles
- Muscles that power flight attach to the inside
of the thorax, not the wings themselves.
- Change in thorax shape forces the wings up
and down.
- Maximises power given the limited space
inside the exoskeleton.
- Muscles that attach to the wing are small
and only control wing orientation.
Hovering
- If your body is not moving, wings have to
move back and forth somehow.
