The Magnus effect (2) The Flettner rotor ship

Описание: The flow past a rotating circular cylinder results in a transverse thrust, i.e. lift force, acting in a direction perpendicular to the upstream flow direction. The effect of the cylinder rotation and associated circulatory flow (resulting from the rotation) is to increase the velocity of the flow on one side of the cylinder [Bottom] and to decrease it on the other [Top]. In turn, the Bernoulli equation implies that the pressure next to the lower and upper walls must be respectively lower and greater than the static pressure. This thrust is referred to as the Magnus effect.
One practical application is the rotor ship, which uses rotating cylinder(s) as sail(s). Designed by Anton Flettner, the first rotor ship used the Magnus effect as main propulsion technique. The "Buckau" sailing ship [Left] was re-designed by mounting two large vertical circular cylinders on the ship and then mechanically rotating the cylinders to provide circulation, hence ship propulsion. The ship, renamed "Baden-Baden" [Right], successfully crossed the Atlantic Ocean. Each cylinder was 18.5m long with a 2.8m diameter.
More recently, a similar system was developed for the ship "Alcyone" of Jacques-Yves Cousteau. The propulsion system of the Alcyone was developed by the French academic Lucien Malavard. It consists of two identical fixed masts (i.e. Turbosail™) equipped with a boundary layer suction system: height: 10.2 m, maximum chord: 2.05 m, width: 1.35 m, surface area: 21m2 (per mast), suction fan: 25 hp, construction: aluminium.
Indeed, the flow around a cylindrical body with circulation: e.g., the Turbosails™ of the Alcyone ship, is a related form of Magnus effect. Boundary layer suction is generated on one side of the cylinder by a suction fan installed inside the mast, while a flap controls the flow separation downstream. The resulting effect is a large fluid circulation around the sail and a significant lift force (CL ∼5 to 6). Optimum performances are obtained when the angle between wind and ship directions ranges between 50 deg. and 140 deg..
In 1926, a cargo ship was equipped with three Flettner rotors (Seifert 2012). The ship was used for 6 years, mostly in the Mediterranean Sea, demonstrating their functionality and reliability even in adverse conditions. Under 4-6 Beaufort winds, the rotors propulsed the ship at 6 knots. During a 6-months testing period, the rotors operated for 30-40% of the trip duration and increased the top speed by 2-3 knots. In very recent years, rotors were installed on cargo ships as auxiliary power to reduce fuel consumption.
The Magnus effect is a classical illustration of ideal fluid flow theory applied to the flow past a rotating cylinder. Its applications, incl. the Flettner rotor ship, remain fascinating more than 170 years after its initial discovery.
A basic understanding of the fluid dynamics processes is critical in many real-word applications. These discussed in a number of relevant Youtube video movies in the same Playlist at:
{   / @hubert_chanson  }

Fluid mechanics and hydraulics in Hubert Chanson Youtube channel {   / @hubert_chanson  }
Applied hydrodynamics [Playlist]
Advanced hydraulics of open channel flows [Playlist]

Streamlines {   • Streamlines  }
Reynolds number {   • Reynolds number  }
Bernoulli equation in open channel flows {   • Bernoulli equation in open channel flows  }
Magnus effect (1) Presentation
Joukowski foil {   • Joukowski foil  }

Acknowledgements
Prof. Colin J. APELT
Equipe Cousteau

References
MAGNUS, H.G. (1853). "The Drift of Shells." Poggendorf’s Annals, Germany.
FLETTNER, A. (1925). "The Flettner Rotor Ship. The Utilisation of Aerodynamical Knowledge for the propulsion of Ships by Wind." Engineering, Jan. 23, pp. 117-120.
SEIFERT, J. (2012). "A review of the Magnus effect in aeronautics." Progress in Aerospace Sciences, Vol. 55, pp. 17-45.
VOGEL-PRANDTL, J. (2014). "Ludwig Prandtl. A Personal Biography Drawn from Memories and Correspondence." Göttinger Klassiker der Strömungsmechanik , Universitätsverlag Göttingen, Germany, 263 pages (ISBN: 978-3-86395-160-3).
CHANSON, H. (2014). "Applied Hydrodynamics: An Introduction." CRC Press, Taylor & Francis Group, Leiden, The Netherlands, 448 pages & 21 video movies (ISBN 978-1-138-00093-3).