Establishment of Effective Metamodels for Seakeeping Performance in Multidisciplinary Ship Design Optimization

Ship design is a complex multidisciplinary optimization process to determine configuration variables that satisfy a set of mission requirements. Unfortunately, high fidelity commercial software for the ship performance estimation such as Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are computationally expensive and time consuming to execute and deter the ship designer's ability to explore larger range of optimization solutions. In this paper, the Latin Hypercube Design was used to select the sample data for covering the design space. A comprehensive seakeeping evaluation index, The percentage of downtime, a comprehensive seakeeping evaluation index, was also used to evaluate the seakeeping performance within the short-term and long-term wave distribution in the Multidisciplinary Design Optimization (MDO) process. The five motions of ship seakeeping performance contained roll, pitch, yaw, sway and heave. Particularly, a new effective approximation modelling technique—Single-Parameter Lagrangian support vector regression （ SPL-SVR ） was investigated to construct ship seakeeping metamodels to facilitate the application of MDO. By considering the effects of two ship speeds, the established metamedels of ship seakeeping performance for the short-term percentage downtime are satisfactory for seakeeping predictions during the conceptual design stage; thus, the new approximation algorithm provides an optimal and cost-effective solution for constructing the metamodels using the MDO process. An accurate and effective prediction technique for seakeeping performance plays an important role in the hydrodynamic-based Multidisciplinary Design Optimization (MDO) for ships. In order to obtain the accurate result of seakeeping prediction, firstly a high-precision calculation method is required in the preliminary ship design stage, for example the strip theory rather than empirical regression models which are widely used in ship seakeeping prediction (Özüm, 2011). Secondly, the adopted calculation method for seakeeping can be easily integrated into the MDO process without any artificial intervention. Thirdly, perhaps the most important part is to minimize the computational cost and complexity. In our previous research, the simulation codes for ship resistance and seakeeping performance were implemented in the(MDO) (LI et al., 2013; LI et al., 2012a; LI et al., 2012b)[References in brackets should be listed chronologically first, then alphabetically (when more than one reference published in the same year)], unfortunately the calculation were