Groundspeed/Airspeed of insect

  • #1
Hi all,

I am involved in a project to fly small moths down a wind tunnel to measure their flight patterns.
the moths fly a total of 1.15m into a headwind of 1m/s. i am currently using velocity=distance/time to calculate an average speed but am unsure if this would be a called a groundspeed or airspeed?? most moths take about 6 seconds to fly this distance.
does anyone have any ideas? other thoughts about how to calculate these velocities?

cheers

goldfinger820
 

Answers and Replies

  • #2
2,985
15
That is the ground speed. You are measuring it relative to a fixed ground frame.
 
  • #3
FredGarvin
Science Advisor
5,066
9
Airspeed is the speed relative to the air. Groundspeed is relative to the ground. The 1.15/6 m/s is the ground speed. The airspeed is 1.15+1 m/s.

Airspeed is used for performance calculations like max lift, etc... Groundspeed is used to calculate time of flight.
 
  • #4
surely airspeed would be groundspeed-windspeed (which in this case would be negative 1m/s due to it being a headwind)?
 
  • #5
russ_watters
Mentor
20,238
6,809
It is negative if it is a tailwind, not a headwind.
 
  • #6
Danger
Gold Member
9,607
247
And any angle between forward and backward results in intermediate values. Despite my total lack of math ability, I could work out wind-vector triangles like a demon. (Gotta love that Cessna flight computer. :biggrin: )
What I really want to know is how you convince a moth to fly upwind rather than down. :uhh:
 
  • #8
960
0
surely airspeed would be groundspeed-windspeed (which in this case would be negative 1m/s due to it being a headwind)?
I suppose it depends on convention--I would thing Sg=Sa+Sw surely if we were talking velocies, this is the case. So the airspeed=2.15m/s as fred suggested. In fact if we were to raise the windspeed to this value, I believe :


Sg=0. Sw=-2.15 and the Sa=2.15
 

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