No I have not. Are you talking about an oscillating fan?
For example, yes.
The point was originally brought up by regatta organisers who would be putting several of these next each other. If the fan from one is blowing against the intake of the next, how is the downwind one not cheating?
And (of course) Concept2 said not to worry, that their rotor speed and acceleration measurement system was robust enough to detect that and compensate. Which of course implies it's also robust enough to compensate for altitude differences in regatta sites.
So I'm wondering if anyone actually experimented on their own - other than just changing damper settings.