Hull form optimization of a cargo ship for reduced drag

Hydrodynamic optimization of the hull forms can be realized through the implementation and integration of computational tools that consist of a hydrodynamic module, a hull surface representation and modification module, and an optimization module. In the present paper, a new bulbous bow generation and modification technique has been developed and integrated into the hull surface representation and modification module. A radial basis function based surrogate model is developed to approximate the objective functions and reduce the computing cost. A multi-objective artificial bee colony optimization algorithm is implemented and integra- ted into the optimization module. To illustrate the integrated hydrodynamic optimization tools, a cargo ship is optimized for reduced drag. The optimal hull forms obtained are then validated computationally and experimentally. Validation results show that the prese- nt tools can be used efficiently and effectively in the simulation based design of the hull forms for reduced drag.

Optimization of press bend forming path of aircraft integral panel

In order to design the press bend forming path of aircraft integral panels,a novel optimization method was proposed, which integrates FEM equivalent model based on previous study,the artificial neural network response surface,and the genetic algorithm.First,a multi-step press bend forming FEM equivalent model was established,with which the FEM experiments designed with Taguchi method were performed.Then,the BP neural network response surface was developed with the sample data from the FEM experiments.Furthermore,genetic algorithm was applied with the neural network response surface as the objective function. Finally,verification was carried out on a simple curvature grid-type stiffened panel.The forming error of the panel formed with the optimal path is only 0.098 39 and the calculating efficiency has been improved by 77%.Therefore,this novel optimization method is quite efficient and indispensable for the press bend forming path designing.

“City-Scene” Characteristics and Optimization Strategies Research on Three Gorges Reservoir Area of the Post-Three Gorges Era

In the long-term symbiotic evolution process,the town areas along the Yangtze River and its natural and cultural landscapes have presented a sound "city-scene" landscape form. But with the implementation of the Three Gorges project,the town relocation as well as the flooding in the natural and human landscape area,the original harmonious "city-scene" pattern started to collapse and fell into the situation of "fragmentation" and "islanding". The differentiation between city and landscape,uncoordinated scale and fractured urban context become pressing issues that affect the integral form optimization of the town areas. This paper aims at responding to the call of the government about proceeding the construction of the Yangtze River economic belt under the ecological and green strategy and seeking an attuned "cityscene" relationship of the town area. Based on the analysis of the dynamic evolution of the "city-scene" relationship,the paper also pointed out that the urban construction around the reservoir area in the postThree Gorges era was the key stage of "scene-city" integration and symbiosis while the maintenance of scenery pattern,the harmony of space scale and the protection of living culture should be applied as the vital strategies.

Forming-Precision-Driven Structure Design of Hydraulic Press: Methodology and Case Study

The structure stiffness of presses has great effects on the forming precision of workpieces, especially in near-net or net shape forming. Conventionally the stiffness specification of presses is empirically determined, resulting in poor designs with insufficient or over sufficient stiffness of press structures. In this paper, an approach for the structure design of hydraulic presses is proposed, which is forming-precision-driven and can make presses costeffective by lightweight optimization. The approach consists of five steps:(1)the determination of the press stiffness specification in terms of the forming precision requirement of workpieces;(2)the conceptual design of the press structures according to the stiffness and workspace specifications, and the structure configuration of the press;(3)the prototype design of the press structures by equivalently converting the conceptual design to prototypes;(4)the selection of key structure parameters by sensitivity analysis of the prototype design; and(5)the optimization of the prototype design. The approach is demonstrated and validated through a case study of the structure design of a 100 MN hydraulic press.

An overview of simulation-based hydrodynamic design of ship hull forms

This review paper presents an overview of simulation-based hydrodynamic design optimization of ship hull forms. A computational tool that is aimed to accomplishing early-stage simulation-based design in terms of hydrodynamic performance is discussed in detail. The main components of this computational tool consist of a hydrodynamic module, a hull surface modeling module, and an optimization module. The hydrodynamic module includes both design-oriented simple CFD tools and high-fidelity CFD tools. These integrated CFD tools are used for evaluating hydrodynamic performances at different design stages. The hull sur- face modeling module includes various techniques for ship hull surface representation and modification. This module is used to automatically produce hull forms or modify existing hull forms in terms of hydrodynamic performance and design constraints. The optimization module includes various optimization algorithms and surrogate models, which are used to determine optimal designs in terms of given hydrodynamic performance. As an illustration of the computational tool, a Series 60 hull is optimized for reduced drag using three different modification strategies to outline the specific procedure for conducting simulation-based hydrodynamic design of ship hull forms using the present tool. Numerical results show that the present tool is well suited for the hull form design optimization at early design stage because it can produce effective optimal designs within a short period of time.

Aerodynamic design optimization of nacelle/pylon position on an aircraft

The arbitrary space-shape free form deformation （FFD） method developed in this paper is based on non-uniform rational B-splines （NURBS） basis function and used for the integral parameterization of nacelle-pylon geometry. The multi-block structured grid deformation technique is established by Delaunay graph mapping method. The optimization objects of aerodynamic characteristics are evaluated by solving NavierStokes equations on the basis of multi-block structured grid. The advanced particle swarm optimization （PSO） is utilized as search algorithm, which com-bines the Kriging model as surrogate model during optimization. The optimization system is used for optimizing the nacelle location of DLR-F6 wing-body-pylon-nacelle. The results indicate that the aerodynamic interference between the parts is significantly reduced. The optimization design system established in this paper has extensive applications and engineering value.

Evaluation of resistance increase and speed loss of a ship in wind and waves

Given the indication of the IMO’s intent to the application of the EEDI and EEOI,the complete and precise total resistance of a ship and induced speed loss in wind and wave is primarily required.This paper proposed a practicable method to evaluate the total resistance in seaway.Besides the still water resistance,the added resistance due to waves is computed using panel method and the wind resistance is obtained using CFD with the verification of an open wind test and statistical formula.The speed loss is acquired in consideration of the matching of the hull,engine and propeller.A hull optimization method is consequently presented based on the proper resistance evaluation approach.The approach is validated available and the total resistance of a ship could be reduced after hull optimization.©2016 Shanghai Jiaotong University.Published by Elsevier B.V.

Optimizing the solar energy capture of residential roof design in the southern hemisphere through Evolutionary Algorithm

Australia’s national energy system is heavily reliant on coal-fired power plants and requires quick action to de-crease CO_(2)emissions in order to meet the Paris climate change agreement by 2030.As a good alternative to coal power,renewable resources can produce the required energy for Australia while keeping the environment clean.The annual amount of falling solar irradiation in Australia is a few thousand times higher than its energy consumption,but the amount of the collected solar energy is unsatisfactory.In Perth,the sunniest city in Aus-tralia,one-third of the residential dwellings have roof-mounted solar collector systems.However,there have been limited studies into the integration of these systems in building design and it is still unknown which roof design can deliver maximum efficiency based on the local environmental conditions.Therefore,the aims of this study are to determine the optimum residential roof design in Perth,Western Australia and to maximise extracted solar power throughout a year.To reach this aim,a combination of analytical modelling,numerical simulation,and evolutionary algorithm methods have been selected.At first,a series of detailed mathematical calculations were performed in Excel to find the optimum solar collector mounting settings.In the numerical simulation,the exam-ination was repeated in the Rhino-Grasshopper interface to verify the earlier findings and calibrate the chosen simulation package with the help of parametric architecture.In the last step,a wide range of housing roof shapes has been tested by evolutionary algorithm plugin-Galapagos,to find the optimum roof shape design in the given context.Our results show that,unlike the traditional approach and common belief,a roof shape with a 25-degree tilt angle,170-175 azimuth angle,and aspect ratio of 1:1.2 is optimum to gain maximum solar gaining annually.Moreover,this study advances the knowledge of solar capturing by suggesting a new parameter-oblique angle-in finding the optimum roof shape design.After evaluating the importance of the mentioned factors,it is found that,after tilt angle,the oblique angle is the most effective parameter in rooftop solar gaining,higher than roof aspect ratio and azimuth angle.In conclusion,our results demonstrate that an‘oblique shed roof design’can generate 15.7%higher solar radiation compared to the base case.The findings of this study can be applied by architects,construction companies,and householders to optimize the solar gaining in the future of the residential building in Perth.

Highly robust ground moving target detection and relocation method for distributed satellites

The performance of ground moving target detection for distributed satellites will be affected signifi-cantly when there is an image registration error,clutter decorrelation and array error.In this paper,a new approach to moving target detection and relocation is proposed based on multi-channel and multi-pixel adap-tive signal processing in an image domain.First,multi-channel and multi-pixel joint data are equated to a simple array model.Given that there is an image registration error,the real steering vector of the moving target can be estimated through a space projection approach.The optimal beam forming approach is used to cancel clutter,and at the same time the cross-track velocity of the mov-ing target can be determined by searching for the peak value of the cost function.The moving target can then be relocated on the SAR image.The simulation results indicate that this method has a good robustness to image registration error,clutter decorrelation and array error.The detection performance and the estimation accuracy are significantly improved.