When you put one fan in front of you and one behind, it can happen, that you have no air movement in the middle. When they have nearly the same speed they compensate each other, because the air can’t move in bove directions simultaneously.
When you put one fan in front of you and one behind, it can happen, that you have no air movement in the middle. When they have nearly the same speed they compensate each other, because the air can’t move in bove directions simultaneously.