Flying Flashcards
Is flight density higher or lower then water?
Lower. 800 fold
What is the main issue when moving through air?
Weight
What do wings do?
Support lift and weight and over come drag
Is the Re number high and what forces dominate?
Yes and inhertia forces
What does the angle of attack do?
Allows air to pass through the airfoils
What are chambers?
Measure of the airfoils curvature
What does a chamber do?
Allows airfoils to create greater velocity differential
What does velocity differential do?
Pressure differential
What is lift?
Pressure differential causes a net upward force that acts perpendicular to airflow
What are flow patterns?
Shows a circular component of airflow
How are vortecies shed?
By circulation development along the wing at at the tip
How can vortecies be seen?
By adding illuminated practical seeded into the air
How to make greater lift?
Increase in airflow and circulation larger wingspan
Where does drag act?
Parallel to air flow
What does increasing the angle of attack do?
Increases lift
What happens when angle of attack is at 45°
Lift decreases and drag increases. Will cause a stall
What can controlled stalling do?
Sharp reduction in circulation and flow allows bird to land
What does rapid flapping do?
Can delay stalling for take off and landing
What else does flapping do?
Flapping causes a forward component which alters airflow in the direction the animal is going. Has a lift and forward component which overcomes drag
Negative lift
Air is above the wing/ symmetrical airfoils which will reverse circulation
What is aspect ratio?
Tip to tip length of wings in ratio to body
Long narrow wings are?
High AR
Short stubby wings are?
Low AR
Advantages of low AR
Decrease in I’m just and increase in maneuverability. Seen in diving seabirds
What is wing loading?
Area of wingspan in proportion to body
What is wing platform area?
Area exposed to airflow
Why is changing wing area important?
Helps birds and bats with landing and maneuverability
What does collapsing the wing do?
During upperstroke reduces drag and avoids negative lift
Low wing loading?
Large slow wings
High wing loading?
Small fast wings
Why do bats operate with low wing loading?
Increases maneuverability
What helps overcome drag when flying?
Induced drag, body drag and profile drag
What is body drag?
Resistance to airflow over the body
What is profile drag?
Results from pressure and skin friction drag operating on the wings
Induced drag?
Low AR wings achieve lower drag performance by the circulation being shed at the tip as a vortex
What does gliding flight represent?
Unpowered flight. Little metabolic energy is used
What do gliders do?
Transform potential energy into aerodynamic work
What is equilibrium gliding?
Lift and drag forces act on the wing to balance the weight and descend at a constant speed
What birds perform equilibrium gliding?
High AR
What does minimizing the angle of attack do?
Maximizes distance in gliding
What are areobal gliders?
Squirrels etc
What do areobal gliders do?
Take off in vertical and horizontal directions and continuously change their gliding angle to help control their landing.
What AR do areobal gliders have?
Low AR
What is parashunting?
When a glide angle exceeds 45°
Can heavy gliders be a problem?
Yes because they travel faster. Tend to be lightweight
What is soaring?
Specialised gliding where animals take advantage of energy from environment
What is static soaring?
Involves slope and thermal soaring
Advantages of soaring?
Saves 65% of energy and good survalance for prey
What is slope soaring?
A guys of wing from up a hill or over a cliff face. Provides energy to keep the bird aloft
What is thermal soaring?
Vultures and hawks utilize the energy from rising hot air. Warm air rises as a vortex ring. The hot air within the vortex rises quickly
How do bird use thermal soaring?
By gliding in a circular motion with the upward current of air and gain altitude
What is dynamic soaring?
Involves the use of energy from the velocity gradient of air on the surface of the sea or land. Used by seabirds
How do seabirds take advantage of velocity gradient of air?
By flying in a spiral path descending downwards to gain velocity.
How does the spiral path work?
By defending downwards at high speed then turning on the oceans surface to fly upwards and turning using kinetic energy gained.
What does low wind velocity at the sea surface do?
Allows birds to reduce drag and fly upwards
What happens when the bird begins to asked from the sea surface?
A gust of wind gains more altitude before starting the spiral flight pattern again
What does the downward stroke do in vertebrates?
Fully extends the wing and produces the work needed for weight and thrust
How do hummingbirds and bees hover?
By rotating the wing during the upstroke to reverse the orientation so further thrust can be generated.
What did humming birds evolve?
Shoulder and wrist articulations that allows them to change their wing to positive angle of attack during upstroke
What else have birds and bats evolved?
Flex in the wing which reduces drag and negative lift during upstroke
What is the shape of the wing stroke for hovering?
Horizontal figure of 8
What is the shape for slow fight?
Left down diagonal figure of 8
What is the shape for fast flight?
Left down diagonal circular motion
