My question is how fan blade design relates to the focus of the air leaving the fan. I am looking to generate the most focused breeze I can with a fan blade, excluding additional ducting etc, the fan is in an open-air environment.
I see a mix of blade types available with different properties - a low number of very broad blades. A high number of narrow blades. A low number of narrow blades. Similarly I see designs where the blade flares towards the tips, and others where it tapers towards the tips, or where the blade is the same width from base to tip.
I have full control over the motor at hand so assume I can turn a fan blade at whichever RPM would be optimal for it.
Which type of blade design, if any, provides the most focused output airflow?
I'm also somewhat interested in what (if any) role the fan housing plays in this,(eg completely unhoused fan blades vs a circular enclosure around the blade tips, or a square enclosure like a box fan) however my primary interest is in the impact of blade design.