Penpal
Crowing
An American University, I think Penn State, experimented with a stock of bales (straw or hay) for sheep. The sheep piled onto the protected side, then a few fewer a step away, and a fewer still and so on until there were like 3 at the end. Imagine a triangle with the longest side up against the bales, then trickling down to the point. This showed them pretty much how the wind was shielded on the non windy side, but less and less so until it offered no protection. This might be the study you are thinking of.