after midterm 2 Flashcards
‘Simple’ gliding
loss of altitude in still air
exchanges height (potential energy) for horizontal velocity and distance
How to gluide
when gliding in still air, the animal must adopt a downward glide path that shifts the relative wind such that the lift is tilted forwards and the resultant aerodynamic force equals the weight of the glider
What happens n a steeper angle of decent when gliding
lift tilted forwards providing a force to balance the rearward drag. Total aerodynamic force (resultant) is now equal and opposite to the weight while the forward component of lift offsets drag
How to soar
have local wind come from bellow then speed of updraft (vertical component of the wind) will offset the sink rate of the glider.
4 types of soaring
Declivity or slope soaring
Thermal soaring
Sea-anchor soaring
dynamic soaring
What is Slope soaring
gliding in a updraft which produces the same aerodynamic result as gliding down through still air. Except gliding in still air requires a loss of altitude- gliding in a sufficiently fast updraft does not. If the vertical component of the wind is greater than the gliders sink speed then it can gain altitude
On a glide polar how to add rising air
add the airspeed of a thermal with a rising airspeed to the y axis, shifting the starting point of your line from the origin: this changes the best airspeed to fly for max distance.
A shallower glide angle…
increases the distance travelled by increasing the time spent in air that is moving upwards and offsetting sinking speed
If airspeed of rising thermal exceeds the sink rate what happens?
the glider will gain altitude at a rate equal to the difference between actual sinking speed and rising air speed.
If goal is to gain altitude as quickly as possible in rising air, the min sink speed will always produce the fastest altitude gains.
A thermal occurs by
1- sun heats ground, warming up air above it
2- a bubble of warm air rises from the ground through cooler air
3- as it rises it cools and expands- cumulus clouds often form at the top of a rising thermal
Structure of a thermal vortex
As air bubble rises due to thermal it is shaped like a donut (toroidal vortex)
as bubble rises up through still air, the air on —outside is being dragged backwards due to shearing with non-heated air
-center is what is being moved up
If a glider wants to ride a thermal what must they do
They should fly in middle and in a circle so they fly through the upward moving air as the thermal is circular in cross-section
Structure of a thermal column
is a continuous plume of rising warm air. Formed by essentially the same processes that produce a thermal vortex, except that the rising air column doesn’t break into discreet bubbles
How to travel in a circle
-an object in motion will move in a straight line unless acted on by a force
-Thus any motion in a curved path represents accelerated motion
- requires a force directed towards the center curvature of the path (a centripetal force)
Centripetal force
= m * (v^2/r)
the force acting towards the center of a circle (center seeking)
