  A Wells turbine is an axial-flow turbine consisting of a rotor usually with
symmetric (uncambered) blades staggered at a 90 degree angle relative to the
incoming flow. This turbine is used within oscillating water column (OWC)
systems, which convert the sea-wave motion into a bi-directional flow of air.
During its normal operation, the turbine blades experience a continuous change
in incidence angle. that according to many authors is at the origin of an
hysteresis in its force coefficients. Aerodynamic hysteresis in rapidly moving
airfoils is a well-known phenomenon, but happens only at non-dimensional
frequencies significantly larger than the ones encountered in Wells turbine.
This work presents a re-examination of the two phenomena, that shows the
unlikeliness of the presence of any aerodynamic hysteresis in Wells turbines. A
simple and efficient lumped parameter analysis is used to prove how the real
cause of the hysteresis is likely to be found in a completely different
phenomenon, overlooked by many previous experimental and numerical analyses.
