• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.173-176
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• 2004

In this study, the multidisciplinary aerodynamic-structural optimal design is carried out for the supersonic fighter wing. Through the aeroelastic analyses of the various candidate wings, the aerodynamic and structural performances are calculated such as the lift coefficient, the drag coefficient and the deformation of the wing. In general, the supersonic fighter is maneuvered under the various flight conditions and those conditions must be considered all together during the design process. The multi-point design, therefore, is deemed essential. For this purpose, supersonic dash, long cruise range and high angle of attack maneuver are selected as representative design points. Based on the calculated performances of the candidate wings, the response surfaces for the objectives and constraints are generated and the supersonic fighter wing is designed for better aerodynamic performances and less weights than the baseline. At each design point, the single-point design is performed to obtain better performances. Finally, the multi-point design is performed to improve the aerodynamic and structural performances for all design points. The optimization results of the multi-point design are compared with those of the single-point designs and analyzed in detail.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.389-390
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• 2006

• Wind and Structures
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• 제29권2호
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• pp.139-147
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• 2019

One of the most important factors in tall buildings design in urban spaces is wind. The present study aims to investigate the aerodynamic behavior in the square and triangular footprint forms through aerodynamic modifications including rounded corners, chamfered corners and recessed corners in order to reduce the length of tall buildings wake region. The method used was similar to wind tunnel numerical simulation conducted on 16 building models through Autodesk Flow Design 2014 software. The findings revealed that in order to design tall 50 story buildings with a height of about 150 meters, the model in triangular footprint with aerodynamic modification of chamfered corner facing wind direction came out to have the best aerodynamic behavior comparing the other models. In comparison to the related reference model (i.e., the triangular footprint with sharp corners and no aerodynamic modification), it could reduce the length of the wake region about 50% in general. Also, the model with square footprint and aerodynamic modification of chamfered corner with the corner facing the wind could present favorable aerodynamic behavior comparing the other models of the same cluster. In comparison to the related reference model (i.e., the square footprint with sharp corners and no aerodynamic modification), it could decrease the wake region up to 30% lengthwise.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.130-133
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• 2008

In this paper the trust region method is studied and applied in aerodynamic shape optimization. The trust region method is a gradient-based optimization method, but it is not as popular as other methods in engineering computations. Its theory will be explained for unconstrained optimization problems and a trust region subproblem will be solved with the dogleg method. After verifying the trust region method with analytical test problems, it is applied to aerodynamic shape design optimization and the performance of airfoil is improved successfully.

• 한국항공우주학회지
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• 제41권3호
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• pp.173-184
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• 2013

본 연구에서는 프로펠러나 헬리콥터 로터와 같은 회전체의 공력 최적 설계를 위한 다단 최적 설계 프레임워크를 제안한다. 이 프레임워크는 플랜폼 설계와 단면의 형상 설계를 반복적으로 수행하는 설계 전략을 통해 회전체의 공력 성능 향상을 목표로 한다. 플랜폼 설계의 단계에서는 유전 알고리즘과 2차원 CFD 데이터베이스 기반의 깃 요소 모멘텀 이론을 이용하여 빠른 시간에 회전체의 공력 특성을 평가하여 최적점을 탐색하였다. 플랜폼 설계 후 단면에 유입되는 유동 조건을 예측하여 단면 형상 최적 설계를 수행하였다. 설계 과정에서 보다 면밀하게 유동 특성이 분석될 수 있도록 2차원 N-S 해석자와 민감도 기반의 최적화 알고리즘을 통해 최적해를 탐색하였다. 단면 형상이 설계된 후에는 최적의 유동 조건을 산출할 수 있도록 플랜폼 설계를 반복적으로 수행하였다. 본 프레임워크를 1kW급 전기추진용 항공기 프로펠러 설계에 적용하여 그 유효성을 3차원 N-S 해석과 풍동 실험을 통해 검증하였다. 설계 후, 풍동 실험 결과를 기준으로 약 5%의 프로펠러 효율 증가를 얻을 수 있었다.

• 한국전산유체공학회지
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• 제17권4호
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• pp.56-68
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• 2012

Nowadays, Unmanned Combat Air Vehicle(UCAV) has become an important aircraft system for the national defense. For its efficiency and survivability, shape optimization of UCAV is an essential part of its design process. In this paper, shape optimization of UCAV was processed for aerodynamic performance improvement and Radar Cross Section(RCS) reduction using Multi Objective Genetic Algorithm(MOGA). Lift and induced drag, friction drag, RCS were calculated using panel method, boundary layer theory, Physical Optics(PO) approximation respectively. In particular, calculation applied Radar Absorbing Material(RAM) was performed for the additional RCS reduction. Results are indicated that shape optimization is performed well for improving aerodynamic performance, reducing RCS. Further study will be performed with higher fidelity tools and consider other design segments including structure.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.403-413
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• 2017

Dual-point aerodynamic design optimization is conducted for DLR-F6 wing-body-nacelle-pylon configuration adopting an efficient surface mesh movement method for complex junction geometries. A three-dimensional unstructured Euler solver and its discrete adjoint code are utilized for flow and sensitivity analysis, respectively. Considered design conditions are a low-lift condition and a cruise condition in a transonic regime. Design objective is to minimize drag and reduce shock strength at both flow conditions. Shape deformation is made by variation of the section shapes of inboard wing and pylon, nacelle vertical location and nacelle pitch angle. Hicks-Henne shape functions are employed for deformation of the section shapes of wing and pylon. By the design optimization, drag coefficients were remarkably reduced at both design conditions retaining specified lift coefficient and satisfying other constraints. Two-point design results show mixed features of the one-point design results at low-lift condition and cruise conditions.

• 한국항공우주학회지
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• 제32권10호
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• pp.12-19
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• 2004

3차원 날개의 공력형상 설계최적화를 위한 설계최적화 시스템을 미래의 다분야 설계최적화 프레임워크의 일환으로 개발하였다. 이 설계최적화 시스템은 형상설계, 격자생성, 공력해석, 최적화의 4가지 모듈로 구성되어있다. 모두 상용패키지를 배경으로 개발하였으며 내장된 스크립트와 저널링 기능을 사용하여 배치 모드에서 자동적으로 실행되도록 프로그램 하였다. Visual Basic 프로그램을 사용하여 네 모듈을 통합하여 자동화된 설계기능을 갖도록 하였다. 특히 계산시간이 많이 소요되는 공력해석을 위하여 네트워크 통신을 이용한 분산 환경을 구현하였다. 공력해석은 일반적인 영역분할방식의 병렬처리 대신에 전역최적화 기법인 반응표면법과 연계하여 분산처리 시켰다. 개발한 공력설계 시스템의 검증을 위하여 간단한 항력최소화 문제에 적용하였으며 그 결과 상당히 향상된 설계 효율성과 적절한 설계 결과를 보여주었다.

• International Journal of Fluid Machinery and Systems
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• 제9권2호
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• pp.143-149
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• 2016

In this study, a method for the multi-objective optimization of an impeller for a centrifugal compressor using fluid-structure interaction (FSI) and response surface method (RSM) was proposed. Numerical simulation was conducted using ANSYS CFX and Mechanical with various configurations of impeller geometry. Each design parameter was divided into 3 levels. A total of 15 design points were planned using Box-Behnken design, which is one of the design of experiment (DOE) techniques. Response surfaces based on the results of the DOE were used to find the optimal shape of the impeller. Two objective functions, isentropic efficiency and equivalent stress were selected. Each objective function is an important factor of aerodynamic performance and structural safety. The entire process of optimization was conducted using the ANSYS Design Xplorer (DX). The trade-off between the two objectives was analyzed in the light of Pareto-optimal solutions. Through the optimization, the structural safety and aerodynamic performance of the centrifugal compressor were increased.

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