I was reading this website that described a novel wind turbine technology and it has this quote:
In the mid-20th century, open propeller-driven planes with piston engines reached performance limits as blade tip speeds neared the speed of sound.
In my mechanical engineering thermal-fluids class I vaguely remember there being some discussion about the change in turbine/compressor design needed for supersonic speeds, but I don't remember any of the concepts or equations. Why does it matter that the tip of the turbine reaches the speed of sound? Does it have any relation to the airspeed approaching from the front of the turbine?
Is whatever sonic phenomena also independent of the size of the turbine? Like a very rotationally-slow but super large radius turbine?
EDIT: to clarify, the company is not claiming anything in particular about the speed of sound in their technology but rather drawing some kind of vague comparison between the limitations of propellers back in the day and how they are supposedly overcoming the same sort of technological barrier.
The question is what does the speed of sound have to do with limiting the ability of a propeller? It is not obvious to me why it's important that a propeller can't break the sound barrier.