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Voyage performance of ship fitted with Flettner rotor
Published in Pentti Kujala, Liangliang Lu, Marine Design XIII, 2018
Osman Turan, Tong Cui, Benjamin Howett, Sandy Day
This research focuses on one of effective wind assist technologies – Flettner rotor. A Flettner rotor is a smooth cylinder with disc end plates which is spun along its long axis and, as air passes at right angles across it, the Magnus effect causes an aerodynamic force to be generated in the third dimension (Seifert, 2012). A rotor ship is a type of ship designed to use the Magnus effect for propulsion (Betz, 1925; Nuttall et al, 2016). The ship is propelled, at least in part, by large vertical rotors (Wikipedia-Rotor ship). German engineer Anton Flettner was the first to build a ship which attempted to tap this force for propulsion in 1920s, so Flettner rotors are also named after their inventor. Rizzo (1925) discussed the fundamental principles of the Flettner rotor ship in the light of Kutta-Joukowski theory. Actually, this technology is treated indifferently since it was first deployed. But these years, with the development of technology and proposition of “low carbon shipping” concept, people are turning their attention back to rotors as an immense potential measure (Howett et al, 2015). They made many achievements on Flettner rotor technology. In 2008, the German wind-turbine manufacturer Enercon launched a new rotor ship, E-Ship 1 (as shown in Fig. 1) and claimed that it can save up to 25% fuel compared to same sized conventional vessels after 170,000 sea miles in 2013 (Enercon, 2013). In 2014, Norsepower Company developed a “Norsepower Rotor sail solution” which is a modernized version of the Flettner rotor (Norsepower, 2014). They installed two Norsepower Rotos on a RoRo vessel “M/V Estraden” in 2014 and later 2015, and announced that this technology has potential for fuel savings of up to 20% for vessels with multiple, large rotors traveling on favourable wind routes (Norsepower, 2016). In 2016, Viking Line also considers the rotor concept for their next planned new building. They showed a new 63,000 GT vessel with large Flettner rotors which could help the ship to save up to 15% fuel consumption (Viking Line, 2016). Besides, Traut et al (2012) assessed the wind power performance of a bulk carrier fitted with three Flettner rotors on the route from Brazil to UK and suggested possible fuel savings of 16%. They also (2014) researched the average power contribution from the Flettner rotor on the analysed routes ranges from 193 kW to 373 kW. When three Flettner rotors are fitted on a 5500dwt cargo carrier, they could provide more than half of the required main engine power under slow-steaming condition. De Marco (2016) analysed the Flettner rotor performance with the method of unsteady Reynolds averaged Navier-Stokes simulations and also presented the applicability of such device for marine applications.
Numerical investigation for coupled rotor/ship flowfield using two models based on the momentum source method
Published in Engineering Applications of Computational Fluid Mechanics, 2021
Zhao Dingxuan, Yang Haojie, Yao Shuangji, Ni Tao
For rotor/ship coupled flowfield analysis, the momentum source method is commonly used in the literature. Shi et al. (2017) compared the vorticity and velocity of a rotor/ship coupled flowfield between a steady rotor model based on the momentum source method and an unsteady rotor model with the moving overset mesh method. The result showed that the main characteristics of the shedding vortex from the rotors are similar and both models reflect the flowfield coupling phenomena well. To analyze the operational behaviors for a helicopter pilot during a shipboard landing when there are two helicopters in the coupled flowfield, Shi et al. (2020) developed a numerical method based on the DES and momentum source method, and the results showed that a large vortex in the headwind condition is the main factor affecting the landing operation. Under unsteady cases, Su, Xu, et al. (2019) used the moving overset mesh method and momentum source method to analyze the rotor loads during a coaxial-rotor helicopter vertical landing on the SFS2 ship. The result suggests that the collective control input and differential collective pitch are the two main reasons for stabilizing the heading of the helicopter, and the moving overset mesh method provides a good solution for rotor simulation under unsteady simulation. Based on the momentum source method, Oruc et al. (2015) developed a virtual fully coupled helicopter/ship dynamic interface using the actuator disk model (ADM), and then a comparison was made with the one-way coupled helicopter shipboard simulation. The results showed that the fully coupled simulation could reasonably capture the trailing vortices generated from the main rotor and the aerodynamic coupling effect of the main rotor downwash and ship airwake. In this paper, the rotor forces are distributed spatially with a one-dimensional Gaussian distribution and then the forces are interpolated into the grids using source terms. This has been shown to help in stabilizing and speeding up the numerical calculations. This method was also used in a real-time helicopter shipboard flight simulation and showed good results in reducing computational costs (Oruc et al., 2016).