I understand you mean free stream. Do you mean free stream at hub height or at the height of a given element?
Marshall
Well, if we neglect the variation in the earth boundary layer, the wind speed should be constant over the rotor shouldn’t it? In any case, I would probably need the hub-height wind speed. But there is a difference between the hub height wind speed and the wind speed upstream of the turbine and it’s related to the normal induction factor. I just need to calculate the latter. My conundrum is that the induction factor depends on that wind speed.
The equation I posted on January 19 gives the free-stream wind speed. It does not include induction effects.
Marshall