My intuition says most airflow comes from the center(and drops linearly towards the tip of the blade and picks up at the blade)
i.e. there's no need to build a filter the size of the fan; you can cover "most" of the airflow by using something similar but extends 50-60% of blade length(pure guess) and the whole arrangement can be above the rotating plane (so easier build?)
i.e. there's no need to build a filter the size of the fan; you can cover "most" of the airflow by using something similar but extends 50-60% of blade length(pure guess) and the whole arrangement can be above the rotating plane (so easier build?)