Is It Groundspeed or Airspeed for Moth Flight in a Wind Tunnel?

[goldfinger820]

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

 

[Cyrus]

That is the ground speed. You are measuring it relative to a fixed ground frame.

 

[FredGarvin]

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.

 

[goldfinger820]

surely airspeed would be groundspeed-windspeed (which in this case would be negative 1m/s due to it being a headwind)?

 

[russ_watters]

It is negative if it is a tailwind, not a headwind.

 

[Danger]

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. )
What I really want to know is how you convince a moth to fly upwind rather than down.

 

[goldfinger820]

surely that can't be right - the insects fly into a headwind so the windspeed must be a negative number (see http://www.aerospaceweb.org/question/instruments/q0210.shtml)
using a positive number gives an airspeed of -0.8m/s!

moths and most other animals fly into head winds for tracking purposes

 

[denverdoc]

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