Hydrodynamic Shape Optimization of Semi-Submersibles Using a Genetic Algorithm

Mahdi Adjami ； Mehdi Shafieefar

《Journal of Marine Science and Technology》 16卷2期 (2008/06) Pp. 109-122

https://doi.org/10.6119/JMST.200806_16(2).0004

並列摘要

This paper presents an automated optimization procedure for adjustment of semi-submersibles shapes to environmental conditions based on a simple genetic algorithm. The proposed procedure combines numerical and statistical tools of CAD, CFD, and probabilistic theory of wave loads to evaluate and optimize the seakeeping behavior of semi-submersibles in an automated process, which is controlled by genetic algorithms (G.A.). In this procedure, starting from an initial design defined by form parameters, new optimum structures with superior seakeeping qualities are developed in subsequent generations. Assessment of the seakeeping behavior is based on linear system assumptions and spectral analysis. Wave-body interactions are evaluated by a three-dimensional diffraction radiation theory, which is suitable for the analysis of arbitrarily shaped bodies. The short-term environmental conditions are described by standard energy density spectra of wave elevation. For the relevant modeling of long-term wave climate, scatter diagrams of the joint probability of significant wave height and mean zero-up-crossing period are integrated in the assessment process. The achievement of combining genetic algorithm and advanced analysis are illustrated by applications which prove the precise adoption of important system parameters like added mass, damping coefficients, and exciting forces to design conditions and environmental characteristics. The presented results show convincing improvements of seakeeping characteristics due to shape optimization.

並列關鍵字

parametric design ； semi-submersibles ； heave motion ； shape optimization ； genetic algorithm ； seakeeping ； hydrodynamic ； analysis