I am looking at fan curves here at work and I stumbled upon this one. Its for an 80mm diameter tube axial fan. What's up with the Flowrate vs RPM curve (the dashed line)? In the flowrate interval between 12 - 23 CFM there are instances of the same RPM for different flowrates. That doesn't make sense to me For a fixed geometry and a fixed RPM how on earth can we have different flowrates? Unless it is accounting for blade deformation? Any thoughts?