"Wire" is effectively the air passing around a cylinder.
There is a lot of information about airflow around cylinders. Eg [1]. The top left diagram should be the one that applies with small diameters and the kind of airflow rates in a PC fan.
I would guess that all the other shapes have micro-scale sharp edges that leave vortexes which both slow the flow down and make noise.
There is a lot of information about airflow around cylinders. Eg [1]. The top left diagram should be the one that applies with small diameters and the kind of airflow rates in a PC fan.
I would guess that all the other shapes have micro-scale sharp edges that leave vortexes which both slow the flow down and make noise.
[1]: https://i.ytimg.com/vi/pW0JfEBE9h8/maxresdefault.jpg