• 대한조선학회논문집
• /
• 제49권2호
• /
• pp.174-181
• /
• 2012

In this paper, the Flow Control Fin(FCF) optimization has been carried out using computational fluid dynamics(CFD) techniques. This study focused on evaluation for the performance of the FCF attached in the stern part of the ship. The main advantage of FCF is to enhance the resistance performance through the lift generation with a forward force component on the foil section, and the propulsive performance by the uniformity of velocity distribution on the propeller plane. This study intended to evaluate these functions and to find optimized FCF form for minimizing viscous resistance and equalizing wake distribution. Four parameters of FCF are used in the study, which were angle and position of FCF, longitudinal location, transverse location, and span length in the optimization process. KRISO 300K VLCC2(KVLCC2) was chosen for an example ship to demonstrate FCF for optimization. The optimization procedure utilized genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results showed that the optimized FCF could enhance the uniformity of wake distribution at the expense of viscous resistance.

• 대한조선학회논문집
• /
• 제44권2호
• /
• pp.139-147
• /
• 2007

The ultimate goal of structural design is to find the optimal design results which satisfies both safety and economy at the same time. Optimum design has been studied for the last several decades and is being studied. in this study, an optimum algorithm which is based on the genetic algorithm has been applied to the multi-object problem to obtain the optimum solutions which minimizes structural weight and construction cost of panel blocks in ship structures at the same time. Mathematical problems are dealt at first to justify the reliability of the present optimum algorithm. And then the present method has been applied to the panel block model which can be found in ship structures. From the present findings it has been seen that the present optimum algorithm can reasonably give the optimum design results.

• 한국유체기계학회 논문집
• /
• 제7권2호
• /
• pp.7-13
• /
• 2004

In an attempt to solve multiobjective optimization problems, weighted sum method is most widely used for the advantage that a designer can consider the relative significance of each object functions by weight values but it can be highly sensitive to weight vector and occasionally yield a deviated optimum from the relative weighting values designer designated because the multiobjective function has the form of simple sum of the product of the weighting values and the object functions in traditional approach. To search the design solution agree well to the designer's weighting values, we proposed new multiobjective function which was the functional of each normalized objective functions and considered to find the design solution comparing the distance between the characteristic line and the ideal optimum. In this study, proposed multiobjective function was applied to design high efficiency and low noise axial flow fan and the result shows this approach is effective for the case that the quality of the design can be highly affected by the designer's subjectiveness represented as weighting values in multiobjective design optimization process.

• 한국산학기술학회논문지
• /
• 제12권3호
• /
• pp.1063-1069
• /
• 2011

오늘날, 차량의 성능 향상에 따라 타이어에 대한 요구가 다양화 되고 요구성능이 고도화됨에 따라 타이어의 설계기술에 보다 다양한 기반기술들이 적극적으로 사용되기 시작하였으며, 이에 대한 많은 연구 중 타이어 형상의 최적화를 통한 타이어 성능 향상을 위한 연구들이 활발히 진행되고 있다. 타이어 형상은 운전성능, 회전저항성, 내구성, 승차감, 소음, 내마모성 등과 같은 차량의 주요성능에 직접적인 영향을 미치는 대단히 중요한 설계인자이다. 따라서 본 연구에서는 실험계획법의 하나인 직교배열표와 회귀식을 이용하여 타이어 형상설계 시에 필요한 유한요소 해석시간을 단축시키고 유전자 알고리듬을 이용하여 타이어의 주요 성능을 만족하는 다목적 형상최적설계를 수행하였다.

• 대한기계학회논문집A
• /
• 제21권11호
• /
• pp.1765-1772
• /
• 1997

The layered composites have a character to change of structure stiffness with respect to the layup angles. The deformations in the fan-blades to be initially designed by considering efficiency and noise, etc., which arise due to the pressure during the fan operation, can make the fan inefficient. Thus, so as to minimize the deformations of the blades, it is needed to increase the stiffness of the blades. An investigation has been performed to develop the three dimensional layered composite shell element with the drilling degree of freedom and the optimization module for finding optimal layup angles with sensitivity analysis. And then they have been verified. In this study, the analysis model is engine cooling fan of automobile. In order to analyzes the stiffness of the composite fan blades, finite element analysis is performed. In addition, it is linked with optimal design process, and then the optimal angles that can maximize the stiffness of the blades are found. In the optimal design process, the deformations of the blades are considered as multiobjective functions, and this results minimum bending and twisting simultaneously.

• 대한산업공학회지
• /
• 제43권3호
• /
• pp.164-175
• /
• 2017

Dual response surface optimization (DRSO) attempts to optimize mean and variability of a process response variable using a response surface methodology. In general, mean and variability of the response variable are often in conflict. In such a case, the process engineer need to understand the tradeoffs between the mean and variability in order to obtain a satisfactory solution. Recently, a Posterior preference articulation approach to DRSO (P-DRSO) has been proposed. P-DRSO generates a number of non-dominated solutions and allows the process engineer to select the most preferred solution. By observing the non-dominated solutions, the DM can explore and better understand the trade-offs between the mean and variability. However, the non-dominated solutions generated by the existing P-DRSO is often incomprehensive and unevenly distributed which limits the practicability of the method. In this regard, we propose a modified P-DRSO using multiple objective genetic algorithms. The proposed method has an advantage in that it generates comprehensive and evenly distributed non-dominated solutions.

• 한국경영과학회지
• /
• 제32권1호
• /
• pp.77-91
• /
• 2007

In this paper, we present a symbiotic evolutionary algorithm for multi-objective optimization. The goal in multi-objective evolutionary algorithms (MOEAs) is to find a set of well-distributed solutions close to the true Pareto optimal solutions. Most of the existing MOEAs operate one population that consists of individuals representing the entire solution to the problem. The proposed algorithm has a two-leveled structure. The structure is intended to improve the capability of searching diverse and food solutions. At the lower level there exist several populations, each of which represents a partial solution to the entire problem, and at the upper level there is one population whose individuals represent the entire solutions to the problem. The parallel search with partial solutions at the lower level and the Integrated search with entire solutions at the upper level are carried out simultaneously. The performance of the proposed algorithm is compared with those of the existing algorithms in terms of convergence and diversity. The optimization problems with continuous variables and discrete variables are used as test-bed problems. The experimental results confirm the effectiveness of the proposed algorithm.

• 산업경영시스템학회지
• /
• 제35권1호
• /
• pp.181-187
• /
• 2012

Various computer-based simulation tools such as 3D-CAD and CAE systems are widely used to design automotive body structure at the early phase of design. Designers must search the optimal solution that satisfies a number of performance requirements by using their tools and a trial-and-error approach. In the previous three reports, a set-based design approach has been proposed for achieving design flexibility and robustness while capturing designer's preference, and its effectiveness has been illustrated with a simple side-door impact beam design problem and real vehicle side-door structure design. This report presents the development of integrated 3D-CAD and CAE system, and the applicability of our proposal for obtaining the multi-objective satisfactory design solutions by applying to an automotive front-side frame.

• 대한조선학회논문집
• /
• 제33권2호
• /
• pp.56-64
• /
• 1996

균일 분포 횡하중이 작용하는 격자형 구조물의 극한 해석법의 개발에 대한 이전의 연구(참고문헌 1과 5)를 검증해 보았고, 붕괴 이론에 있어서 면내력의 영향을 고찰 하였다. 논문의 주된 내용은 최소 중량과 최소 비용을 갖는 격자형 구조물의 최적설계법을 개발하였고, Pareto 해석법을 적용하여 다목적 함수를 갖는 구조물에서 최적 절충해를 구하는 최적화 기법을 소개하였다.

• 대한기계학회논문집B
• /
• 제30권11호
• /
• pp.1084-1092
• /
• 2006

Shape optimization of airfoil in WIG craft has been performed by considering the ground effect. The WIG craft should satisfy various aerodynamic characteristics such as lift, lift to drag ratio, and static height stability. However, they show a strong trade-off phenomenon so that it is difficult to satisfy aerodynamic properties simultaneously. Optimization is carried out through the multi-objective genetic algorithm. A multi-objective optimization means that each objective is considered separately instead of weighting. Due to the trade-off, pareto sets and non-dominated solutions can be obtained instead of the unique solution. NACA0015 airfoil is considered as a baseline model, shapes of airfoil are parameterized and rebuilt with four-Bezier curves. There are eighteen design variables and three objective functions. The range of design variables and their resolutions are two primary keys for the successful optimization. By two preliminary optimizations, the variation can be reduced effectively. After thirty evolutions, the non-dominated pareto individuals of twenty seven are obtained. Pareto sets are all the set of possible and excellent solution across the design space. At any selections of the pareto set, these are no better solutions in all design space.