The equation that calculates airspeed from blower power (3) is given by Mizuno in the patent that Ahlfors helpfully posted.
I do not understand the equations for power (1) and (2), however (3) seems straightforward.
I wonder how well (3) corresponds to the data we actually have? The exact equation is given here.
EDIT: this looks like it must be a different system from that described in the 2018 paper: 5W in the paper delivers ~5m/s air speed whereas from this equation 5W delivers 3.9m/s air speed.