Yan-yun Yu

Refraction and diffraction of random waves through breakwater

A physical model study of combined refraction and diffraction of waves through a breakwater gap at different incident angles was conducted. Both regular and random waves with narrow and broad frequency and direction spreading were studied. Besides the presence of a mild bottom slope in the lee of the breakwater, the distribution of wave heights across the width of a navigation channel inside the model harbor was also simulated. In addition to contributing to an understanding of the phenomenon of refraction and diffraction of random waves, the relatively complete set of data obtained can serve as a benchmark for testing of numerical models.

Numerical modelling of multi-directional irregular waves through breakwaters

Abstract A numerical model based on the time domain solution of the Boussinesq equations using the finite element method is described in this paper. The propagation of multi-directional irregular waves in water of varying depth can be simulated using the present model and there are no limitations on the form of incident waves. The validity of the model had been demonstrated by Li et al. (cf. Y.S. Li et al., Numerical modelling of Boussinesq equations by finite element method, Coastal Engineering 37 (1999) 97–122) using several test cases where the incident wave is sinusoidal. In this paper, the propagation of multi-directional irregular wave over an elliptical shoal was first modelled to demonstrate the versatility of the finite element method. The multi-directional irregular wave diffraction around a semi-infinite breakwater and through a breakwater gap is then simulated to further validate the numerical model. Good agreements are observed between the numerical and experimental results. The results also show that the directional spreading of the incident waves has a significant effect on the wave diffraction and leads to a distinct diffraction contour compared with that of unidirectional waves. The computed results show that the model can be applied to solve practical engineering problems involving multi-directional irregular waves.

A new method for ship inner shell optimization based on parametric technique

ABSTRACT A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

An ant colony optimization–genetic algorithm approach for ship pipe route design

An optimization approach for the problem of the ship pipe route design (SPRD) is presented in this paper, which is based on the ant colony optimization (ACO) algorithm and the genetic algorithm (GA). The main goal of SPRD problem is to design an appropriate pipe route to connect the starting point and end point under the various kinds of constraints. Due to the large layout space, the complex construction in layout space and the great number of pipelines, SPRD becomes a very difficult task. An ACO–GA algorithm is proposed to solve the SPRD problem. Genetic operators including crossover operation and mutation operation in GA are embedded in the computing process of ACO to improve the computing performance of the proposed algorithm. Based on the ACO–GA, an algorithm is proposed to solve the problem of the multiple pipes and the branch pipe routing. The simulation results demonstrate the feasibility and effectiveness of the proposed algorithm.

A Parametric Structure Optimization Method for the Jack-Up Platform

In this paper, A parametric structure optimization method, which is called Parametric Structure Shape Optimization Method (PSSOM), is proposed in order to optimize the structure shape of the jack-up platform. According to the characteristic of the jack-up, an approach to create the Parametric Structure Model (PSM) is proposed. The projections of the main structure onto the horizontal plane are used to create the sketch, which is a 2D drawing driven by dimensions. The 3D modeling technique that based on the sketch and feature modeling is used to create the structure model of the jack-up. A meshing procedure is presented to convert PSM into finite element model automatically together with the boundary conditions and the design loads. After calling the FEM solver, the stress and strain for each structure according to any reasonable dimensions could be calculated, and this is the most important foundation of the structure shape optimization design. An optimization design method based on PSM is proposed for the structure optimization design of the jack-up. The genetic algorithm is used to get the optimum dimensions that have better structure strength performance under the premise of that all the other design requirement are satisfied. PSSOM is proved to be practical and high-efficient by the structure optimization of a 300 ft jack-up platform.© 2012 ASME

An integrated beam-plate structure multi-level optimal design framework based on bi-directional evolutionary structural optimization and surrogate model

Abstract Lots of endeavors have been made to apply optimization techniques to real design problems for various engineering beam-plate structures, however, due to the limitation of traditional topological form and the difficulty of finding the optimal topology in numerous optional design plans, many beam-plate structure designs are not the optimal solution but only a feasible solution. This paper proposes an integrated optimal design framework for beam-plate structure based on combining bi-directional evolutionary structural optimization (BESO) and surrogate model method, which covers three optimization levels, as dimension optimization, topology optimization and section optimization. BESO is used for topology optimization. In order to deal with beam-plate structures, the traditional BESO method is improved by using cubic box as the unit cell instead of solid unit to construct periodic lattice structure. Requirements for the framework are discussed based on the features of beam-plate structure design process first. The proposed framework consists of automated finite element modeling module, structure optimization module and post-processing module. Usefulness of the designed framework is examined through a cantilever beam structure design.

Research on structural optimization method of FRP fishing vessel based on artificial bee colony algorithm

Abstract Due to the increase of the operating cost and material cost, weight reduction has attracted much attention among ship designers and ship owners. Ship structure optimization remains a very complicated problem due to the feasible combinations of structural members with different sections are numerous. In the present work, based on artificial bee colony (ABC) algorithm, we propose a structural design optimization method of fiber reinforced plastic (FRP) ship structure. The objective of the proposed optimization method is to minimize the weight of FRP ship structure under a group of constraints. In order to deal with parametric finite element analysis (FEA) of the whole FRP ship structure, the modeling work is simplified by using beam element instead of shell element to simulate top hat stiffener. To evaluate the applicability of the proposed method, it was applied to a problem for finding optimal structure of a 32.98 m FRP fishing vessel. The result shows that the developed program can decrease the structural weight by about 8.31%. Thus, this study will be able to contribute to make energy saving and environment-friendly ship.