CFD investigation of wind powered ships under extreme conditions

Abstract

With the International Maritime Organization’s (IMO) goal of reducing greenhouse gas emissions 50% by 2050, the design and propulsion of ships must change rapidly. The use of wind propulsion is one solution. A CFD analysis has been performed using the sail geometry of the Oceanbird Ro-Ro ship, with the purpose of determining the forces on the sails. Star-CCM+ has been used to analyze the NACA 0015 wing profile in both 2D and 3D. In 2D, the k − ! SST model has been employed to compare the lift and drag coefficients with wind tunnel data and to show the effects of dynamic stall. In 3D, the IDDES model has been used to compute the lift and drag coefficients with 3D effects and to determine the interaction effects between multiple wings CFD results show that lift and drag forces slightly differ from the forces seen in previous wind tunnel experiments. The physical time plays an important role in the simulations, both in the 2D and 3D situations, what has led to different conclusions, mainly in relation to the setup of the mesh and physics of the investigation. Dynamic stall affects the performance of the wing when rotating from one angle of attack to another, being the biggest determinant the rotational speed. Both the integrity of the structure and the thrust production need to be considered when establishing the dynamic stall situation. In the multiple wing simulations, the rear wing has shown to be severely affected by the leading wing during stalled conditions. Finally, the frequencies of vibrations from vortex shedding have been calculated which are interesting for the structural integrity of the rig, concluding that the stalled situations should be avoided since the shedding frequencies could compromise the structure. Suggestions for further work include wind tunnel tests to confirm the data in this report and a more in-depth structural analysis.