• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.6
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• pp.1-9
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• 2006

본 연구의 목적은 여러 가지 비행 모드 상의 로터 성능을 효율적으로 예측하는 것이다. 헬리콥터의 공력 특성을 예측하기 위한 비정상 source-doublet 패널 기법 기반의 수치 기법을 개발하였다. 후류의 형상 예측에는 시간 전진 자유후류모델이 사용되었다. 점성에 의한 확산을 고려한 후류의 roll-up 모사를 위하여 후류의 doublet 패널은 같은 강도의 와류고리로 대체하여 계산하였다. 후류와 양력면의 충돌 문제는 표면격자 내부에 들어간 와류고리의 포텐셜값을 제거하여 해결하였다. 제자리비행의 해석 시에 나타나는 와류 불안정성의 해결에는 slow starting과 vortex core growth 모델을 사용하였다. 로터 공력 해석 프로그램은 제자리비행과 전진비행에 대한 실험 결과와 비교하여 검증하였으며, 실험치와 일치하는 결과를 얻을 수 있었다.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.1-9
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• 2007

As a first step toward a complete CFD-CSD coupling for helicopter rotor load analysis, the present study attempts to loosely couple a CFD code with a source-double panel method. The far-field wake effects were calculated by a time-marching free vortex wake method and were implemented into the CFD module via field velocity approach. Unlike the lifting line method, the air loads correction process is not trivial for the source-doublet panel method. The air loads correction process between the source-doublet method and CFD is newly suggested in this work and the computation results are validated against available data for well-known hovering flight conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.6
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• pp.367-376
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• 2022

In this study, a steady and unsteady aerodynamic analysis program using a 3-dimensional subsonic unstructured panel method is developed and verified. Surfaces of bodies are modeled with the source and doublet distributions on triangular or quadrilateral panels. Geometry modeling of complex geometries and multi-body, therefore, can be easily accomplished. The Kelvin theory and the unsteady Kutta condition allow the doublet strength of the wake panels determined for unsteady flows. Various steady and unsteady flows in two and three dimensions are computed and compared with the analytical and the published computational results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1066-1072
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• 2009

A panel method based on potential flow theory is developed for the steady/unsteady aerodynamic analysis of arbitrary three-dimensional Blended Wing Body aircraft. The panel method uses the piecewise constant source and doublet singularities as a solution. This potential based panel method is founded on the Dirichlet boundary condition and coupled with the time-stepping method. The present method uses the time-stepping loop to simulate the unsteady motion of the aircraft. The present method can solve the three-dimensional flow over the complex bodies with less computing time and provide various aerodynamic derivatives to secure the stability of Blended Wing Body aircraft. That will do much for practical applications such as aerodynamic designs and analysis of aircraft configurations and flight simulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.638-642
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• 2008

Computational methods based on the solution of the flow model are widely used for the analysis of lowspeed, inviscid, attached-flow problems. Most of such methods are based on the implementation of the internal Dirichlet boundary condition. In this paper, the time-domain panel method uses the piecewise constant source and doublet singularities. The present method utilizes the time-stepping loop to simulate the unsteady motion of the rotary wing blade. The wake geometry is calculated as part of the solution with no special treatment. To validate the results of aerodynamic characteristics, the typical blade was chosen such as, Caradonna-Tung blade and present results were compared with the experimental data and the other numerical results in the single blade condition and two blade condition. This isolated rotor blade model consisted of a two bladed rotor with untwisted, rectangular planform blade. Computed flow-field solutions were presented for various section of the blade in the hovering mode.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.110-120
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• 2006

There have been developed many structural and fluid rotorcraft analysis models in rotorcraft community, and also lots of investigations have been conducted to combine these two models. These investigations turn out to be good at predicting the airloads precisely, but they have not taken the blade nonlinear deflection into account. For this reason, the present paper adopts a sophisticated structural model which can describe three-dimensional nonlinear deflection of the blade. And it is combined with two types of aerodynamic model. First one is generalized Greenberg type of finite-time aerodynamic model, which is originally established for a fixed wing, but later modified to be suitable for coupled flap-lag-torsional aeroelastic analysis of the rotor blade. Second aerodynamic model is based on the unsteady source-doublet panel method coupled with a free wake model. The advantages of the present method are capabilities to consider thickness of the blade and more precise wake effects. Transient responses of the airloads and structural deflections in time domain are mainly analyzed in this paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.799-802
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• 2002

Korea Aerospace Research Institute has been developing a 50-meter class airship to demonstrate the technology to be used in the development of a stratospheric airship, and importance of accurate prediction of the dynamic behavior of an airship before flight test is widely conceived. The added mass has large impact on the dynamic characteristics of an airship unlike for an airplane and the added mass of the airship with empennage is predicted in this paper. At first, the usability of the strip theory is examined which integrates the analytic two dimensional results in the cross section along the longitudinal axis. A panel method with the surface distribution of sources is developed and its validity is also examined. Finally, the panel method with both source and doublet distributions is implemented, and it is validated and applied for the calculation of the added mass of a 50-meter class airship. Using the methods developed, the influence of empennage and control surface deflection on the added mass property of the airship is studied.