• 한국군사과학기술학회지
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• 제1권1호
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• pp.145-153
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• 1998

천음속 날개꼴의 수치최적화 설계에 있어서, 하나의 흐름조건에 의해 설계된 날개꼴의 공력특성은 다른 흐름조건에서 나쁜 특성을 나타낼 수 있다. 따라서, 실용적인 날개꼴의 설계를 위해서 multi-point 수치최적화 설계능력은 필수적인 요소이다. 본 논문에서는 Navier-Stokes 방정식 흐름해석 코드와 feasible direction 최적화 알고리즘을 이용하여 two-point 수치최적화 설계를 수행하였으며, 가중치가 수치최적화 설계에 주는 영향을 분석하고 비교하였다. 그 결과로서 two-point수치최적화 설계된 날개꼴이 두 흐름조건의 주변영역에서 동시에 요구 공력특성을 만족시키며, 가중치가 큰 방향으로 최적화 설계됨을 확인하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.37-42
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• 2001

A computerized axial flow fan design system is developed with the capabilities for predicting the aerodynamic performance and the noise characteristics of fan. In the present study, the basic fan blading design is made by combining vortex distribution scheme with camber line design, airfoil selection, blade thickness distribution and stacking of blade elements. With the designed fan blade geometry, the through-flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with spanwise total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuation induced by wake vortices of fan blades and to radiate as dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fans. Furthermore, the present method is shown to be very useful in designing the blade geometry of new fan and optimizing design variables of the fan to achieve higher efficiency and lower noise level.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.13-20
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• 2014

It is necessary to design a compressor with high pressure ratio that satisfies the IMO(international maritime organization) NOx emission regulation for the marine diesel engine. Impeller was designed using the modified slip factor with the flow coefficient. The main purpose of this study is to investigate the sensitivity of the compressor performance by the vaned diffuser geometries. The first vaned diffuser type was based on a NACA airfoil, the second was channel diffuser, and the third was conformally transformated configuration of a NACA65(4A10)06 airfoil. The sensitivity of the performance was calculated using a commercial CFD program for three different diffuser geometries. The channel diffuser showed the wide range of operation and higher pressure characteristics, comparing with the others. This is attributed to the flow stability at diffuser. Combined with this results with impeller design, the optimized compressor was designed and verified by the test results.

• 한국유체기계학회 논문집
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• 제15권6호
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• pp.11-17
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• 2012

The one way fluid structure interaction analysis on advanced propeller blade for next generation turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. propeller geometry is generated by varying chord length and pitch angle at design point. Blade sweep is designed based on the design mach number and target propulsion efficiency. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and showed the enhanced performance than the conventional propeller. The skin-foam sandwich structural type is adopted for blade. The high stiffness, strength carbon/epoxy composite material is used for the skin and PMI(Polymethacrylimide) is used for the foam. Aerodynamic load is calculated by computational fluid dynamics. Linear static stress analysis is performed by finite element analysis code MSC.NASTRAN in order to investigate the structural safety. The result of structural analysis showed that the design has sufficient structural safety. It was concluded that structural safety assessment should incorporate the off-design points.

• Structural Engineering and Mechanics
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• 제88권4호
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• pp.301-309
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• 2023

In this paper, a new modified conjugate gradient (MCG) method is presented which is based on a new gradient regularizer, and this method is used to identify the dynamic load on airfoil structure without and with considering random structure parameters. First of all, the newly proposed algorithm is proved to be efficient and convergent through the rigorous mathematics theory and the numerical results of determinate dynamic load identification. Secondly, using the perturbation method, we transform uncertain inverse problem about force reconstruction into determinate load identification problem. Lastly, the statistical characteristics of identified load are evaluated by statistical methods. Especially, this newly proposed approach has successfully solved determinate and uncertain inverse problems about dynamic load identification. Numerical simulations validate that the newly developed method in this paper is feasible and stable in solving load identification problems without and with considering random structure parameters. Additionally, it also shows that most of the observation error of the proposed algorithm in solving dynamic load identification of deterministic and random structure is respectively within 11.13%, 20%.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제5권2호
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• pp.39-51
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• 2001

This paper shows how boundary element method can be used to calculate torsion geometrical stiffness of cross-sections of various beams and airfoil profiles. Using the BEM direct formulation, the technique for determining bending and torsional geometrical characteristics of arbitrary multiply connected cross-sections is presented. The application limits of several well-known formulae on some test problems have been demonstrated and discused.

• 한국음향학회지
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• 제40권6호
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• pp.555-565
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• 2021

본 연구의 목표는 냉장고 냉동실 냉기순환용으로 사용되는 후향익 원심팬 시스템을 대상으로 익형의 형상을 최적설계 하여 유동성능 및 소음성능을 향상시키는 것이다. 대상 시스템은 전형적인 원심팬 시스템에서 사용되는 스크롤 하우징 형상 없이 두 개의 Volute가 후면 덕트 시스템과 연계하여 냉기를 공급한다는 특성을 가지고 있다. 먼저 팬 시스템의 유동 및 소음성능을 실험적으로 평가하였다. 유동실험에서 팬 성능 시험기를 사용하여 P-Q 곡선을 도출할 수 있었으며, 무향실에서 소음실험을 통해 소음 스펙트럼을 측정하였다. 다음으로, 3차원 비정상 Navier-Stokes 방정식을 전산유체역학을 사용하여 수치해석하여 유동 특성을 분석하였으며, 예측한 유동장을 입력값으로 Ffowcs Willams-Hawkings방정식을 이용해 소음해석을 수행하였다. 수치해석결과는 실험 결과와 비교를 통해 그 유효성을 검증하였다. 검증된 수치해석 기법을 기반으로 반응표면법의 2인자 중심합성법을 통해 유량이 최대가 되는 입구각 및 출구각을 도출하였다. 마지막으로 최적화된 팬을 대상으로 시제품을 제작하여 실험한 결과 개선된 유량 성능 및 소음성능을 확인하였다.

• 한국항공우주학회지
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• 제37권11호
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• pp.1055-1065
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• 2009

경계층 안정성 방정식인 PSE를 이용하여 익형 표면에 형성되는 경계층의 안정성 해석을 수행하였다. 압축성 비점성 유동 해석으로 경계층 가장자리 조건을 얻고, 일반좌표계에서의 압축성 경계층 방정식을 4차 정확도로 계산하여 층류 경계층 유동장을 얻었다. 층류 경계층 데이터를 PSE의 입력으로 하여 안정성 해석을 수행하고 교란의 증폭률을 얻어 안정성 특성을 고찰 하였다. 마하수 0.5의 NACA0012 및 HSNLF(1)-0213 익형에 대한 해석을 수행하여 교란 주파수에 따른 증폭률 및 위치에 따른 교란의 진폭 분포 특성을 파악하였다. 익형의 윗면과 아랫면에서 받음각에 따른 안정성 특성을 각각 증폭률의 크기와 주파수 범위에 대해 분석하였다. 또한 중립안정성 곡선, 마하수에 따른 안정성 특성을 살펴보았으며 익형의 종류에 따른 안정성 특성 차이를 분석하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.125-129
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• 2005

Flow control has been performed using synthetic jet on NACA23012. In order to improve aerodynamic performance, synthetic jet is located near separation paint on airfoil with leading edge droop and plain flap. The flow control using synthetic jet shows that stall characteristics and control surface performance can be improved through resizing separation vortices. Stall is delayed and stall characteristics are improved when synthetic jet is applied from separation region of leading edge droop. Control surface effectiveness is increased and lift is increased when synthetic jet applied at the flap leading edge region. The results show that aerodynamic characteristics can be improved through leading edge droop with synthetic jet at near separation and plain flap with synthetic jet at the flap leading edge. The combination of synthetic jet and simple high lift device is as good as fowler flap system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.144-149
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• 2012

The transfer matrix method is used to determine the dynamic characteristics(natural frequencies and mode shapes) by rotational speed of wind turbine blade. The problems treated on this study is coupled flapwise bending and chordwise bending of pre-twisted nonuniform wind turbine blade. The orthogonality relations that exist between the vibrational modes is derived and the algorithm for determination of the natural vibrational characteristics is suggested.