Posted: Mar 07, 2011 10:56 am
reksio wrote:Onyx8 wrote:ignoring observations like chaggle just made.
chaggle's "observation" is just a misconception about what "wind" is. Wind means that the entire air mass in the area is moving relative to the ground. The wind doesn't have to "reach the vehicle" as chaggle puts it, because the vehicle is always immersed in air that moves relative to the ground (a.k.a. wind).
reksio wrote:CdesignProponentsist wrote:
From the frame of reference of the vehicle the wind behind it is moving faster. But from the ground frame of reference it has slowed the wind behind it.Davian wrote:
If you are travelling faster that the wind, think of the wind ahead of you as having energy waiting to be taken.
Two important observations, that might help others with the understanding. Although I would replace the word "wind" with the word "air" in both.
Why not be more specific and avoid using such confusing terms altogether?
The airmass has a speed and direction relative to the ground W
The vehicle has a speed and direction relative to the ground Vg
The vehicle will also have an speed and direction relative to the airmass Va
For any given W and Vg you should always be able to determine Va.
Unless Vg is exactly the same as W, the vehicle will be moving within the airmass, so Va will have a speed and direction, and so, in the same way that aircraft can be observed flying towards or away from cumulus clouds (which move with the airmass), the vehicle will either 'reach' or 'outpace' parcels of air in the airmass.
You should then be able to explain more simply, how Va can be used to provide energy to move the vehicle at a speed and direction where the downwind speed component of Vg exceeds the speed component of W.