• 산업기술연구
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• 제25권B호
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• pp.89-97
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• 2005

Application of proper orthogonal decomposition (POD) and continuous wavelet transform (CWT) is introduced to study wind speed and building roof pressures of flow separation region. In this study, a detailed analysis of the approach wind flow, wind-induced building pressure and the relation between the two fields was carried out using the POD technique and CWT analysis. The results show potential of the application of POD and CWT in characterization of spatio-temporal and spectral properties of the approach wind and its induced dynamic pressure events. Some of findings resulting from the application of this analysis can be summarized as follows: (1) The POD first principal coordinate of the roof pressure in the separated shear layer is closely correlated with the longitudinal component of oncoming flow. (2) The CWT analysis suggests that the extreme peak pressure in the separated shear layer is due to condensed large-scale eddy motions.

• 한국항공우주학회지
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• 제33권8호
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• pp.105-110
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• 2005

외부장착 계측포드를 사용한 비행 적합성 시험 결과의 분석 기법을 연구하였다. 자체적으로 개발한 계측포드로부터 획득한 센서 원시자료와 MIL-STD-1553B 원시자료를 각각 별도의 방법으로 분석하였으며, 센서 자료의 보정, 동조 및 동기화를 통해 서로 다른 형태의 두 자료를 동시에 분석할 수 있도록 하였다. 분석 자료의 타당성 평가 결과, 자료가 항공기의 거동을 잘 구현하고 있었으며 실제 비행에서 수행한 자료값과 잘 일치하였다.

• 한국전산유체공학회지
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• 제20권2호
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• pp.7-15
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• 2015

This paper attempts to evaluate the accuracy and efficiency of a design optimization procedure by combining wavelets-based multi resolution analysis method and proper orthogonal decomposition (POD) technique. Aerodynamic design procedure calls for high fidelity computational fluid dynamic (CFD) simulations and the consideration of large number of flow conditions and design constraints. Thus, even with significant computing power advancement, current level of integrated design process requires substantial computing time and resources. POD reduces the degree of freedom of full system by conducting singular value decomposition for various field simulations. In this research, POD combined Design Optimization model is proposed and its efficiency and accuracy are to be evaluated. For additional efficiency improvement of the procedure, multi resolution analysis method is also being employed during snapshot constructions (POD training period). The proposed design procedure was applied to the optimization of wing aerodynamic performance. Throughout the research, it was confirmed that the POD/MRA design procedure could significantly reduce the total design turnaround time and also capture all detailed complex flow features as in full order analysis.

• 한국군사과학기술학회지
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• 제25권1호
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• pp.9-22
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• 2022

A fighter performing a reconnaissance mission is equipped with a pod that drives optical/infrared sensors for acquiring and identifying target information on the lower part of the fuselage. Due to the nature of the reconnaissance mission, the fighter performs high speed evasive maneuvers, and the resulting load should be considered importantly for the development of the pod. This paper concerns a numerical investigation into the inertial and aerodynamic loads of the airborne pod of high performance aircrafts. For the aerodynamic load analysis, the pylon and pod shapes are added to the fighter 3D model, and the commercial software was used for static and dynamic analysis. Considering the practical mission conditions, the common/extreme conditions were established respectively in the static and dynamic situations of pods and the driving torque could be tripled under dynamic conditions. In the analysis of inertia load, a 3-DOF model considering roll and turning maneuvers was derived by the Lagrangian method, and then the numerical integration method was applied to the analysis. As a results, it was conformed that the inertia load was generally induced at a low level compared to the aerodynamic load, but depending on the unbalance mass condition of the pod, the inertia load cannot be negligible.

• 대한조선학회논문집
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• 제49권1호
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• pp.14-25
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• 2012

Recently, the application and installation of the pod propeller to the cruise ship is dramatically increased. It is because pod propulsion system allows a lot of flexibility in design of the internal arrangement of a ship. To reflect this trend, many researches have conducted to use the pod propeller for the roll stabilization of a ship. In the paper, a roll stabilization controller is designed by using fins and pod propellers as the control actuators for cruise ships. Two kinds of control algorithms are adopted for the roll control system; LQR (Linear Quadratic Regulator) algorithm and frequency-weighted LQR algorithm. Through the numerical simulation, the effect of the turning rate of the pod propeller on the roll control system is analyzed. Analysis of the simulation results indicated that the turning rate of the pod propellers is one of the important parameters which give the significant effects on the roll stabilization.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.965-980
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• 2014

This paper presents a new estimation method of full scale propulsive performance for the pulling type podded propeller. In order to estimate the drag of pod housing, a drag velocity ratio, which includes the effects of podded propeller loading and Reynolds number, is presented and evaluated through the comparison of model test and numerical analysis. By separating the thrust of propeller blade and the drag of pod housing, extrapolation method of pod housing drag to full scale is deduced, and correction method of propeller blade thrust and torque to full scale is presented. This study utilized the drag coefficient ratio of the pod housing as a measure for expanding it to full scale, but in order to increase the accuracy of performance evaluation, additional study is necessary on the method for the full scale expansion via separating the drag of pod body, strut and fin which consist the pod housing.

• 한국소음진동공학회논문집
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• 제22권6호
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• pp.495-501
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• 2012

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FE model building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FE model reflecting the results of the modal testing of a pod is built through the optimization and will be applied to the structural dynamic model of an aircraft which is used to verified the stability of vibration and flutter of an aircraft.

• 대한기계학회논문집B
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• 제37권6호
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• pp.567-575
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• 2013

외부경계층 수직 날의 마찰저항 저감 기구를 규명하기 위하여 회류수조에서 시간분해 입자영상유속계로 측정된 비정상 유동장에 POD 분석을 실시하였다. 최근의 PIV 결과에서는 수직날 평면 및 수직날 사이 평면에서 각각 2.73%, 7.95%의 마찰저항 저감효과가 발견되었다. 본 연구에서는 수직날 배열이 난류조직구조에 미치는 영향을 POD 방법을 통하여 분석하였다. 난류유동의 조직적인 와구조가 수직날에 의하여 절단, 변형되고 비정상 거동이 난류경계층에서의 마찰저항 저감 기구와 밀접하게 관련된 것으로 관찰되었다.

• 한국항공우주학회지
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• 제42권5호
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• pp.383-389
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• 2014

하이브리드 로켓 연소실 내부 유동장에 대한 수치계산 결과에 POD기법을 적용하였다. 특히, 다이어프램 설치에 따른 유동모드 변화를 분석하여, 연소특성에 미치는 영향을 해석하였다. 또한, 다이어프램이 있는 연소실에서 표면 분출유동의 유무에 따른 POD를 적용하여 분출유동이 연소실 내부 유동특성에 미치는 영향을 판단하였다. 10개의 모드를 사용하여 기본형상에 대한 POD 결과를 살펴보면 주 유동을 나타내는 모드 1과 벽면 근처의 작은 크기 유동인 2-9 모드 사이의 구분이 분명하게 나타났다. 다이어프램을 설치한 형상의 POD 결과, 모드 2부터 5의 에너지가 증가하였는데 이것은 다이어프램 주변 순환영역에서 생성되는 유동 때문인 것으로 보인다. 한편, 다이어프램 주위 영역의 유동특성을 보여주는 모드 2-5와 후류 벽면의 유동특성을 보여주는 모드 6-9의 에너지 분포가 분출유동 유무에 관계없이 비슷한 특성을 나타냈다. 따라서 연소율이 다이어프램 근처에만 국부적으로 증가하는 이유는 다이어프램 후류에 형성되는 비교적 큰 크기의 유동모드 2-5의 에너지가 증가되었기 때문인 것으로 분석된다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.146-146
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• 2017

The pod shattering or dehiscence is essential for the propagation of pod-bearing plant species in the wild, but it causes significant yield losses during harvest of domesticated crop plants. Identifying novel molecular makers, which are linked to seed-shattering genes, is needed to employ the molecular marker-assisted selection for efficiently developing shattering-resistant soybean varieties. In this study, a genetic linkage map was constructed using 115 recombinant inbred lines (RILs) developed from crosses between the pod shattering susceptible variety, Keunol, and resistant variety, Sinpaldal. A 180 K Axiom(R) SoyaSNPs data and pod shattering data from two environments in 2001 and 2015 were used to identify quantitative trait loci (QTL) for pod shattering. A major QTL was identified between two flanking single nucleotide polymorphism (SNP) markers, AX-90320801 and AX-90306327 on chromosome 16 with 1.3 cM interval, 857 kb of physical range. In sequence, genotype distribution analysis was conducted using extreme phenotype RILs. This could narrow down the QTL down to 153 kb on the physical map and was designated as qPDH1-KS with 6 annotated gene models. All exons within qPDH1-KS were sequenced and the 6 polymorphic SNPs affecting the amino acid sequence were identified. To develop universally available molecular markers, 38 Korean soybean cultivars were investigated by the association study using the 6 identified SNPs. Only two SNPswere strongly associated with the pod shattering. These two identified SNPs will help to identify the pod shattering responsible gene and to develop pod shattering-resistant soybean plants using marker-assisted selection.