Comparison of actuator disc flows representing wind turbines and propellers

Actuator disc theory is the basis for rotor design and analysis, valid for discs representing wind turbine rotors as well as propellers. In Froude's momentum theory swirl is absent, in Joukowsky's momentum theory this is included. The momentum theory including swirl, developed in WES, 2:307-316,2017, as well as potential flow calculations have been expanded to propeller discs. For the rotational speed Ω → ∞ the classical Froude results are recovered. For low values of Ω the propeller discs show an expanding instead of contracting wake, like wind turbine discs. Both flow regimes show a complete blockage of the flow for a low but non-zero Ω min . For all wind turbine discs, so irrespective of Ω, the velocity in the meridian plane, $\sqrt{{v}_{x}^{2}+{v}_{r}^{2}}$ is constant at the disc, for all propeller discs this is not.