• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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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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• 제10권2호
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• pp.23-33
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• 2009

The inherent aeromechanical complexity of a rotor system necessitated the comprehensive analysis code for helicopter rotor system. In the present study, an aerodynamic analysis module has been developed as a part of rotorcraft comprehensive program. Aerodynamic analysis module is largely classified into airload calculation routine and inflow analysis routine. For airload calculation, quasi-steady analysis model is employed based on the blade element method with the correction of unsteady aerodynamic effects. In order to take unsteady effects - body motion effects and dynamic stall - into account, aerodynamic coefficients are corrected by considering Leishman-Beddoes's unsteady model. Various inflow models and vortex wake models are implemented in the aerodynamic module to consider wake induced inflow. Specifically, linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's induced inflow distribution and sectional normal force coefficients of AH-1G. In order to validate unsteady aerodynamic model, 2-D unsteady model for NACA0012 airfoil is validated against aerodynamic coefficients of McAlister's experimental data.

• 한국항공우주학회지
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• 제41권5호
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• pp.335-341
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• 2013

풍동시험 중에 발생하는 시스템오차의 변동에 관한 연구를 수행하였다. 회전익 항공기의 기체 공력특성 측정실험에 실험설계 방법론이 적용되었다. 풍동시험 중에 발생하는 시스템오차의 변동에 관한 연구를 수행하였다. 허용 실험오차 내에서 항상 동일한 결과를 얻어야 하는 전제조건에도 불구하고 한 개의 실험시간 블록에서 측정된 힘과 모멘트가 다른 시간블록에서 측정된 것과 상당량 다르게 측정되었다. 실험관련 시스템오차는 존재하지 않는다고 임의로 간주해서는 안되며 이러한 오차의 감소는 랜덤화, 블록화 및 반복화 등의 실험설계원리의 적용을 통해 가능하다.

• 한국항공우주학회지
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• 제42권4호
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• pp.291-297
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• 2014

회전익 항공기의 기체 공력특성 측정실험에 실험설계 방법론을 적용하여 풍동실험의 정밀도 향상에 관한 연구를 수행하였다. 블록화와 블록화 되지 않은 경우들에 대한 분산분석결과의 비교를 통해 블록화의 영향을 평가하였다. 2차 반응표면모델의 경우 블록화가 실험결과의 정밀도 향상에 실질적인 영향을 주고 있음을 알 수 있었다. 본 연구를 통해 랜덤화, 블록화 및 반복화와 같은 실험설계원리와 같은 풍동실험 절차의 재배치를 통해 이러한 정밀도 향상이 가능함을 보였다.

• 한국추진공학회지
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• 제1권2호
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• pp.84-90
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• 1997

다목적으로 활용할 수 있는 분리축방식의 터보축 엔진 개발을 위한 정상상태 해석 프로그램의 개발과 함께 동일한 형식의 가스터빈엔진 시험장치를 이용한 실험을 통해 프로그램의 해석결과와 비교, 그 타당성을 입증하였다. 실험에 이용된 시험장치는 1단 원심형 압축기, 인통형 연소기, 1단 원심형 압축기 터어빈 및 동력 터어빈으로 구성되어 있으며 출력은 3상 교류발전기를 통해 획득된다. 해석에 사용된 주요 구성품의 성능곡선은 시험장치 제작자로부터 획득된 자료를 이용하였으며, 경우에 따라 시험장치를 이용한 실험을 통하여 보정하였다. 시험장치를 이용한 실험결과를 프로그램 해석결과와 비교한 결과, 시험장치의 운용제한에 의해 실제 작동영역이 제한되기는 했으나, 압력비, 출력 등 주요 변수들에서 6％ 미만의 오차를 보였다.

• Steel and Composite Structures
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• 제37권4호
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• pp.419-429
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• 2020

Composite structures are generally pressurized at both sides when repaired by the scarf repair method. But single-face vacuum bag curing (SVC) may be used in some practical scarf repair of penetration damage due to the low accessibility of composite structures, which can decrease bonding quality and may reduce structural mechanical properties. In this paper, experimental investigations were conducted on tensile and compressive properties of scarf-repaired composite laminates using SVC and double-face vacuum bag curing (DVC) in four hygrothermal environments. Finite element models of composite scarf joints with voids were established to further explore the failure mechanism of scarf-repaired laminates. Results show that the curing condition hardly affects tensile and compressive properties of the repaired laminates though it significantly affects the bonding quality with adhesive inner voids. Failure loads of scarf joints almost keep unchanged with adhesive voids increasing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 춘계학술대회논문집; 부산수산대학교, 10 May 1996
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• pp.361-369
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• 1996

The accurate prediction of modal parameters of a rotating blade is an important requirement in the assessment of the dynamics of a helicopter rotor. Indeed, predictions of flight loads and stability are normally dependent on initially predicting the undamped mode shapes. A measuring technique, known as Strain Pattern Analysis (SPA), appears to be the most successful technique for measuring the mode shapes of rotating blades. This method was developed to be used on actual aircraft so no attempt was made to measure rotating mode shapes directly in order to validate the SPA method. This report summarizes results from experimental investigations which were carried out to validate the SPA method for the prediction of aerodynamically damped modes of a rotating blade. A series of modal tests were carried out on two rotor models in which the non-rotating, undamped and aerodynamically damped rotating modes were measured directly (strain and displacement patterns). It is shown that the SPA method to be very successful in itself but there are a number of limitations in validating this technique. To provide data which could be used to confidently validate theoretical prediction codes, existing limitations should be addressed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.163-168
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• 2000

A method to search the design parameters for optimum stage matching has been used based on a 1-D mathematical model of a compressor, which uses the data obtained from the preliminary test to identify the design parameters. This methodology was applied with a two-stage axial compressor, which was originally designed for a helicopter gas turbine engine. After Identifying design parameters using preliminary test data, an optimization process has been employed to achieve the best matching between the stages (i.e., maximum efficiency of the compressor at its operation modes within a given range of the rotor speed under given restrictions for required stall margins and mass flow). 3-D flow calculations have been performed to confirm the usefulness of the corrections based on 1-D mathematical model. Calculational results agree well with the experimental data in view of the performance characteristics. Some promising results were produced through the methodology proposed in this paper in conjunction with flow calculations.

• 한국전산유체공학회지
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• 제17권1호
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• pp.54-60
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• 2012

Transition prediction results are validated with experimental data obtained from a transonic wind tunnel for the KU109C airfoil. A Reynolds-Averaged Navier-Stokes code is simultaneously coupled with the transition transport model of Langtry and Menter and applied to the numerical prediction of aerodynamic performance of the KU109C airfoil. Drag coefficients from the experiment are better correlated to the numerical prediction results using a transition transport model rather than the fully turbulent simulation results. Maximum lift coefficient and drag divergence at the zero-lift condition with Mach number are investigated. Through the present validation procedure, the accuracy and usefulness of both the experiment and the numerical prediction are assessed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.9-12
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• 1999

This paper presents the development of a control architecture for the autonomous underwater vehicle (AUV) with VARIVEC (variable vector) propeller. Moreover this paper also describes the new technique of controlling the servomotors using the Field Programmable Gate Array (FPGA). The AUVs are being currently used fur various work assignments. For the daily measuring task, conventional AUV are too large and too heavy. A small AUV will be necessary for efficient exploration and investigation of a wide range of a sea. AUVs are in the phase of research and development at present and there are still many problems to be solved such as power resources and underwater data transmission. Further, another important task is to make them smaller and lighter for excellent maneuverability and low power. Our goal is to develop a compact and light AUV having the intelligent capabilities. We employed the VARIVEC propeller system utilizing the radio control helicopter elements, which are swash plate and DC servomotors. The VARIVEC propeller can generate six components including thrust, lateral force and moment by changing periodically the blade angle of the propeller during one revolution. It is possible to reduce the number of propellers, mechanism and hence power sources. Our control tests were carried out in an anechoic tank which suppress the reflecting effects of the wall surface. We tested the developed AUV with required performance. Experimental results indicate the effectiveness of our approach. Control of VARIVEC propeller was realized without any difficulty.