Comparison of full 3D-RANS simulations with 2D-RANS/lifting line method calculations for the flow analysis of rigid wings for high performance multihulls

This paper reports about a comparison of a 3D RANS investigation to calculate the flow around wing sails with a method based on 2D RANS calculations of flow around wing profiles in conjunction with a lifting line method to account for 3-dimensional flow phenomena. The investigation focusses on rigid wings with two elements: a main element with a hinged flap, as they are currently used on some performance multihulls. Wing sails can be analyzed using conventional 3D RANS flow investigation methods; however the computational costs are quite high. Here an alternative approach is introduced. It is based on planar flow 2D RANS profile investigations in conjunction with a lifting line method to account for 3-dimensional flow phenomena and induced drag. The lifting line method uses an iterative approach to make use of non-linear profile lift coefficients. This approach is so computationally efficient that it can be combined with constrained optimization methods in order to optimize performance of the wing. The paper describes the motivation for the development, the lifting line theory and validation efforts. Some applications of the new method are shown, demonstrating the ability of the method to be used for wing sail design and operation optimization.