Boundary-Element Methods and Wave Loading on Ships
CHALLENGE - A general hydrodynamic problem of a constantly moving rigid body (ship) floating on the free surface, or submerged near the free surface, is presented in this study. The concept of isogeometric analysis (IGA) for bridging the gap between CAD and finite-element analysis (FEA) is investigated. Subsequently, the IGA-BEM method is developed and applied to the numerical solution of steady flow problems around 3D bodies of general shape in parallel stream.
SOLUTION - The hydrodynamic solvers with the developed ship-parametric models are integrated within an optimization environment illustrating the design-through-analysis capabilities of the IGA-BEM approach. Two realistic design problems are presented: a local optimization problem that is related to the optimization of the bulbous shape of a container ship against the criterion of minimum wave resistance and a global optimization problem of a global hull-shape optimization of a container ship for minimizing both the total resistance and deviation from a target deadweight. The employed optimizers for the test cases are the commercial tool modeFRONTIER along with an optimization library, equipped with various algorithms ranging from descent methods to semistochastic algorithms, developed by INRIA.
BENEFITS - The evolution strategy offered by modeFRONTIER is used to calculate the Pareto front of the presented optimization problem. In the case of a 150-ton deviation from the target deadweight, the optimum solution would be a waterline length of 295.5 m. The IGA-BEM concept can contribute toward drastically improving the efficiency and accuracy of calculating ship wave loads and hull-form optimization.