Back to the future? Flettner-Thom rotors for maritime propulsion?

The paper presents the authors’ latest CFD research examining, by way of a range of URANS computations, the performance of spinning cylindrical rotors for maritime propulsion both in the form adopted by Flettner and with discs distributed along the cylinder as proposed by Thom (1934). Computations agree well with experimental data of the bare rotor but indicate that three-dimensional unsteadiness means that a strictly 2-dimensional idealization produces too high lift and too low drag. The addition of discs, while leading toapparently negative drag coefficients, does not produce the striking rise in lift coefficients that Thom’s experiments had shown. Moreover, the great increase in torque coefficients associated with adding discs seemsto exclude their use in sea-going propulsion applications.