• 제목/요약/키워드: experimental aerodynamics

검색결과 128건 처리시간 0.025초

2단 경가스총에 대한 실험적 연구 (Experimental Study on a Two-Stage Light-Gas Gun)

  • 이중근;김희동;구자예
    • 한국추진공학회지
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    • 제14권4호
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    • pp.10-15
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    • 2010
  • Two-stage light-gas gun은 짧은 시간동안 초고압을 발생시키기 용이하므로, 현재까지 고속충격역학, 발사체 공기역학, 재료역학 등 다양한 공학 분야에서 활용되어 왔다. 일반적으로 2단식 경가스총은 고압실, 압축실 그리고 발사관으로 비교적 간단한 구조로 구성되며, 각 부분은 격막에 의해 구분되어있다. 본 연구는 2단식 경가스총을 초고압 액체 제트 분사에 적용하기 위한 기초적 연구로서, 고압실 하류에 설치된 제1격막의 파막 압력의 변화에 따른 발사체의 속도 변화 및 관내 압력 거동을 조사하였다. 그 결과, 제1격막이 파막 되는 압력은 피스톤의 가속에 큰 영향을 미치며, 피스톤이 가속될수록 고압을 생성하는데 용이하였다.

상용 프로펠러 공력 데이터베이스 구축을 위한 실험적 연구 (An Experimental Study for Construction of Aerodynamic Database of the Commercial Propeller)

  • 심호준;김건홍;천혜진
    • 항공우주시스템공학회지
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    • 제15권5호
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    • pp.60-71
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    • 2021
  • 상용 프로펠러의 추력과 토크를 측정하기 위한 성능시험 장치를 고안하였으며, 30인치급 3가지 프로펠러에 대한 성능시험을 수행하였다. 프로펠러 추력과 토크 측정을 위해 모터, 프로펠러와 연결된 6분력 발란스를 적용하였으며, 풍동 저울 교정 장비를 이용하여 측정 시스템의 확인을 수행하였으며, QTP 프로펠러를 적용하여 구축한 성능시험 장치의 검증 시험도 수행하였다. 제자리 비행 조건에서 상용 프로펠러의 제작사에서 제공하는 사양과 시험 결과를 비교하였으며, 추력 및 토크에서 차이가 있음을 확인하였다. 받음각, 프로펠러 형상, 풍속을 변경시켜가며 프로펠러 성능을 측정하였으며, 각 프로펠러에 대해 RPM에 따른 프로펠러 추력 계수로 나타내었다. 저 받음각과 고 받음각에서 경향이 다르게 나타남을 확인하였으며, 차후 공중용 무인이동체 공력 설계에 활용 가능한 공력 데이터베이스를 확보하였다.

Validation of a 750 kW semi-submersible floating offshore wind turbine numerical model with model test data, part II: Model-II

  • Kim, Junbae;Shin, Hyunkyoung
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제12권1호
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    • pp.213-225
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    • 2020
  • Floating Offshore Wind Turbines (FOWT) installed in the deep sea regions where stable and strong wind flows are abundant would have significantly improved energy production capacity. When designing FOWT, it is essential to understand the stability and motion performance of the floater. Water tank model tests are required to evaluate these aspects of performance. This paper describes a model test and numerical simulation for a 750-kW semi-submersible platform wind turbine model-II. In the previous model test, the 750-kW FOWT model-I suffered slamming phenomena from extreme wave conditions. Because of that, the platform freeboard of model-II was increased to mitigate the slamming load on the platform deck structure in extreme conditions. Also, the model-I pitch Response Amplitude Operators (RAO) of simulation had strong responses to the natural frequency region. Thus, the hub height of model-II was decreased to reduce the pitch resonance responses from the low-frequency response of the system. Like the model-I, 750-kW FOWT model-II was built with a 1/40 scale ratio. Furthermore, the experiments to evaluate the performance characteristics of the model-II wind turbine were executed at the same location and in the same environment conditions as were those of model-I. These tests included a free decay test, and tests of regular and irregular wave conditions. Both the experimental and simulation conditions considered the blade rotating effect due to the wind. The results of the model tests were compared with the numerical simulations of the FOWT using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code from the National Renewable Energy Laboratory (NREL).

BO-105 헬리콥터 복합재 로터 블레이드 역설계 (Reverse Design for Composite Rotor Blade of BO-105 Helicopter)

  • 이창배;장기주;임병욱;신상준
    • 한국항공우주학회지
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    • 제49권7호
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    • pp.539-547
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    • 2021
  • 회전익 항공기의 로터 블레이드는 공기역학, 구조적 유연성, 제어 가능성 등의 상호작용 효과를 고려한 설계가 필요하다. 역설계는 형상정보 및 실험결과를 통해 공통된 특성을 갖는 구성품을 설계할 때 유용하게 사용될 수 있다. 본 논문에서는 BO-105 헬리콥터의 복합재 로터 블레이드를 선정하여 공통된 특성을 갖도록 역설계하고자 하였다. 이를 위해 로터 블레이드를 여러 구간으로 나누어 복합재료가 단면에 따라 연속적으로 적층될 수 있도록 역설계를 수행하였다. 각 구간에 대해서는 variational asymptotic beam sectional analysis (VABS) 단면해석 프로그램을 사용하여 설계안의 플랩 방향, 래그 방향 및 비틀림 강성값이 실험 결과와 일정 수준 이하의 차이를 갖도록 하였다. 최종으로 CAMRAD II를 통해 특정 비행 조건에서 로터 블레이드에 작용하는 하중을 예측한 후 설계된 블레이드가 구조적으로 유효한지 확인하였다.

T-GDI 엔진의 속도 및 하중이 블로우바이 가스의 오일입자 크기와 오일분리기 성능에 미치는 영향에 대한 실험 및 수치적 연구 (Experimental and Numerical Investigation of the Effect of Load and Speed of T-GDI Engine on the Particle Size of Blow-by Gas and Performance of Oil Mist Separator)

  • 정수진;오광호
    • 한국분무공학회지
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    • 제25권4호
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    • pp.162-169
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    • 2020
  • The worldwide focus on reducing the emissions, fuel and lubricant consumption in T-GDI engines is leading engineers to consider the crankcase ventilation and oil mist separation system as an important means of control. In today's passenger cars, the oil mist separation systems mainly use the inertia effect (e.g. labyrinth, cyclone etc.). Therefore, this study has investigated high efficiency cylinder head-integrated oil-mist separator by using a compact multi-impactor type oil mist separator system to ensure adequate oil mist separation performance. For this purpose, engine dynamometer testing with oil particle efficiency measurement equipment and 3D two-phase flow simulation have been performed for various engine operating conditions. Tests with an actual engine on a dynamometer showed oil aerosol particle size distributions varied depending on operating conditions. For instance, high rpm and load increases bot only blow-by gases but the amount of small size oil droplets. Submicron-sized particles (less than 0.5 ㎛) were also observed. It is also found that the impactor type separator is able to separate nearly no droplets of diameter lower than 3 ㎛. CFD results showed that the complex aerodynamics processes that lead to strong impingement and break-up can strip out large droplets and generate more small size droplets.

Aerodynamic properties of a streamlined bridge-girder under the interference of trains

  • Li, Huan;He, Xuhui;Hu, Liang;Wei, Xiaojun
    • Wind and Structures
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    • 제35권3호
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    • pp.177-191
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    • 2022
  • Trains emerging on a streamlined bridge-girder may have salient interference effects on the aerodynamic properties of the bridge. The present paper aims at investigating these interferences by wind tunnel measurements, covering surface pressure distributions, near wake profiles, and flow visualizations. Experimental results show that the above interferences can be categorized into two primary effects, i.e., an additional angle of attack (AoA) and an enhancement in flow separation. The additional AoA effect is demonstrated by the upward-moved stagnation point of the oncoming flow, the up-shifted global symmetrical axis of flow around the bridge-girder, and the clockwise-deflected orientation of flow approaching the bridge-girder. Due to this additional AoA effect, the two critical AoAs, where flow around the bridge-girder transits from trailing-edge vortex shedding (TEVS) to impinging leading-edge vortices (ILEV) and from ILEV to leading-edge vortex shedding (LEVS) of the bridge-girder are increased by 4° with respect to the same bridge-girder without trains. On the other hand, the underlying flow physics of the enhancement in flow separation is the large-scale vortices shedding from trains instead of TEVS, ILEV, and LEVS governed the upper half bridge-girder without trains in different ranges of AoA. Because of this enhancement, the mean lift and moment force coefficients, all the three fluctuating force coefficients (drag, lift, and moment), and the aerodynamic span-wise correlation of the bridge-girder are more significant than those without trains.

Multi-fidelity uncertainty quantification of high Reynolds number turbulent flow around a rectangular 5:1 Cylinder

  • Sakuma, Mayu;Pepper, Nick;Warnakulasuriya, Suneth;Montomoli, Francesco;Wuch-ner, Roland;Bletzinger, Kai-Uwe
    • Wind and Structures
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    • 제34권1호
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    • pp.127-136
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    • 2022
  • In this work a multi-fidelity non-intrusive polynomial chaos (MF-NIPC) has been applied to a structural wind engineering problem in architectural design for the first time. In architectural design it is important to design structures that are safe in a range of wind directions and speeds. For this reason, the computational models used to design buildings and bridges must account for the uncertainties associated with the interaction between the structure and wind. In order to use the numerical simulations for the design, the numerical models must be validated by experi-mental data, and uncertainties contained in the experiments should also be taken into account. Uncertainty Quantifi-cation has been increasingly used for CFD simulations to consider such uncertainties. Typically, CFD simulations are computationally expensive, motivating the increased interest in multi-fidelity methods due to their ability to lev-erage limited data sets of high-fidelity data with evaluations of more computationally inexpensive models. Previous-ly, the multi-fidelity framework has been applied to CFD simulations for the purposes of optimization, rather than for the statistical assessment of candidate design. In this paper MF-NIPC method is applied to flow around a rectan-gular 5:1 cylinder, which has been thoroughly investigated for architectural design. The purpose of UQ is validation of numerical simulation results with experimental data, therefore the radius of curvature of the rectangular cylinder corners and the angle of attack are considered to be random variables, which are known to contain uncertainties when wind tunnel tests are carried out. Computational Fluid Dynamics (CFD) simulations are solved by a solver that employs the Finite Element Method (FEM) for two turbulence modeling approaches of the incompressible Navier-Stokes equations: Unsteady Reynolds Averaged Navier Stokes (URANS) and the Large Eddy simulation (LES). The results of the uncertainty analysis with CFD are compared to experimental data in terms of time-averaged pressure coefficients and bulk parameters. In addition, the accuracy and efficiency of the multi-fidelity framework is demonstrated through a comparison with the results of the high-fidelity model.

압축성 대와류모사를 이용한 고속열차의 공력 및 공력소음의 수치적/실험적 분석 (Numerical and experimental analysis of aerodynamics and aeroacoustics of high-speed train using compressible Large Eddy Simulation)

  • 이권기;정철웅;김재환;정민승
    • 한국음향학회지
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    • 제43권1호
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    • pp.95-102
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    • 2024
  • 기술 발전에 힘입어 고속열차의 운항속도는 증가하고 있으며, 고속열차 외부 유동장으로부터 발생하는 공력소음은 설계 단계에서 매우 중요한 고려 대상이 되어왔다. 이러한 고속열차의 유동기인소음을 정확하게 예측하기 위해서는 근거리 음향장에서 고해상도의 음원 발생과 원거리 음향장에서 수치적 소산이 적은 소음 전파가 요구된다. 이는 실제 고속열차의 구성요소 별로 시공간 스케일을 모두 적절하게 고려할 수 있는 수치격자 및 시간해상도가 동반되어야 한다. 이러한 도전점을 극복하기 위해, 본 연구는 실제 크기 및 실제 운행속도의 고속열차 5차량의 외부 유동장 및 음향장을 3차원 압축성 대와류모사(Large Eddy Simulation, LES) 기법을 이용하여 동시 계산하였다. 수치해석의 검증을 위해 벽면압력섭동 측정 결과와 수치해석 결과를 비교하였다. Ffowcs Williams and Hawkings 방정식을 이용하여 고속열차로부터 방사되는 음향파워를 예측하고 주행속도간 결과를 비교분석하였다. 본 연구는 고속열차의 공력소음 발생 메커니즘 분석을 바탕으로 한 소음 저감에 기여할 것으로 사료된다.