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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Aeronautical & Space Sciences
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Journal DOI :
The Korean Society for Aeronautical & Space Sciences
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Volume & Issues
Volume 29, Issue 8 - 00 2001
Volume 29, Issue 7 - 00 2001
Volume 29, Issue 6 - 00 2001
Volume 29, Issue 5 - 00 2001
Volume 29, Issue 4 - 00 2001
Volume 29, Issue 3 - 00 2001
Volume 29, Issue 2 - 00 2001
Volume 29, Issue 1 - 00 2001
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Bas Flow Computation For An Axi-symmetric Nacelle Configuration
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 1~1
Despite the massive effort which has been given to ghe analysis of the base flows, one commonly occurring case seems to be overlooked. This is for base (rearward facing surface) which is between subsonic flow and supersonic flow region. Potential flows of the air and gas streams are computed for the flow past a separated wake. Then a viscous jet mixing is superimposed on this inviscid solution.
Numerical Study on Injecton and Mixing of Secondary Gas into a Supersonic Stream
김경무 ; 백승욱 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 10~10
The present study describes the numerical investigations concerning the injection and mixing phenomena of a secondary gaseous jet through a transverse slot nozzle in a wall into a supersonic stream which is uniform outside of a turbulent boundary layer. The numerical investigations are performed by solving the fully two-dimensional Navier-Stokes equations using Roe's FDS method and the 2nd order implicit TVD scheme. The results show that bow shock wave/turbulent boundary layer interaction induced the boundary layer separation in front of the injection. In interacting flow, when the total pressure ratio or width of injector increased, the interaction region and shock structure considerably changed.
A Study on the Turbulent Characteristics of a Liquid Impinging Jet
강신재 ; 유기완 ; 권기철 ; 조원일 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 20~20
This paper presents the turbulent characteristics of liquid impinging jets such as mean velocity, half width, turbulent intensity, turbulent kinetic energy and turbulent shear stress were measured by the PDPA system. Water was used as a test fluid. The velocity distribution and turbulent characteristics in the doublet injector were investigated at 26000, 39000, 45000 and 52000 of the Reynolds number. As the Reynolds number increased, the half width of the long-axis(b₁) was larger than that of the short-axis(b₂). The maximum value of turbulent intensity was occurred at about Y/b₁=1.3 away from Y/b₁ in the lateral direction. The trend of turbulent kinetic energy and turbulent shear stress was similar to turbulent intensity. With progressing the downstream of the mixed flow, turbulent intensity and turbulent kinetic energy were gradually decreasing at all Reynolds number. These results of this study provide the basis of turbulent properties for improving combustion in the propulsion system.
Dynamic Mode Sensing of a Composite Bean Using Fiber Bragg Grating Sensor
구본용 ; 류치영 ; 홍창선 ; 김천곤 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 27~27
Fiber Bragg grating(FBG) sensor is a kind of the fiber optic sensor (FOS) and offers lots of advantages for structural health monitoring due to its multiplexing capability. Also, it is useful for the measurement of the structural vibration without mass concentration effect. For an accurate measurement of wavelength shift of FBG sensor, we developed a signal processing board with an electric circuit based on time-interval counting. This circuit board supplies tremendously the enhancement of the real-time signal processing program using LabVIEW software. To improve its multiplexing capability for large numbers of sensors, multi-channel sensor arrays with a wavelength-swept fiber laser(WSFL) are also constructed. This sensor system showed a good resolution of dynamic strain (<10 με), sampling rate of 140 Hz and it proved to be effective for real-time strain monitoring of a large structure. To demonstrate the sensor system performance, real-time dynamic strain sensing of multi-points located on a composite beam was executed. From the acquired strains of multi-points, natural frequencies and strain measured mode shapes of the beam were also calculated. The experimental results showed a good agreement with numerical simulation.
Structural Dynamics Modeling and Analysis of Rotating Composite Beams
정성남 ; 노태수 ; 유기호 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 36~36
In this paper, a refined beam formulation has been developed for the structural dynamics modeling and the free vibration analysis of both rotating and non-rotating composite beams and blades. The present approach allows the modeling of either open-section or closed-section beams of arbitrary cross-sectional shape. The theory accounts for the effects of elastic coupling, shell-wall thickness, warping, warping restraint, and transverse shear deformations. A mixed variational approach based on Reissner's semi-complimentary energy functional is used to obtain the kinematic beam force-displacement relations. A finite element method is employed to analyze the free vibration behavior of composite beams. The analysis is validated against experimental test data and other analytical results for elastically coupled composite cantilevered beams of various cross-sections. Good correlation is shown to be achieved for the beams considered.
MMeasurement Method of Strain/Stress in a Variable Temperature Environment and Its Application to Measurement of CTE of a Composite
구남서 ; 권영두 ; 김주식 ; 윤광준 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 43~43
In this work, we investigate a measurement technique of strains and stresses using strain gage in an environment of variable temperature. The concept of a reference compensation strain gage is introduced to eliminate thermal output, or errors due to (1) the temperature dependency of electrical resistance of a grid conductor and (2) the mismatch of CTE(coefficient of thermal expansion) between a strain gage grid conductor and a test sample. We experimentally showed that the present method could measure the strains of an isotropic beam in a variable temperature environment for both free and fixed boundary conditions. Especially, for fixed condition, the values of thermal loads calculated from the measured strain data were compared with those of a load cell. This method was also applied to measure the CTE's of a carbon/epoxy composite.
Numerical Simulation of Damage Propagation and Ductile Fracture using Isotropic Ductile Damage Model
정순완 ; 김승조 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 52~52
The continuum damage model for ductile damage and ductile fracture is applied to metal forming and crack simulation by finite element method. The isotropic damage model is modified from the existing one to include the crack closure effect. And the highly nonlinear equilibrium equation is formulated in order to include geometric, material nonlinearities and frictional contact condition. The difference of damage concentration according to ghe effects of friction is shown in metal forming example. Then we verify that the ductile fracture using this damage model is reasonable by the comparison with the experimental result in CCT(center-cracked tension) specimen. And the crack initiation and propagation in the edge-cracked plate are simulated under the plane stress assumption. And the influence of the hole at the crack tip is shown through the numerical results in several models with different hole size. Finally, the strain energy release rate in this damage model is compared with J-integral using ABAQUS to relate the result of damage analysis with the concepts of fracture mechanics.
A Study on The Effect of Crack Closure for Bending Plate
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 61~61
This paper presents the combination technique of the hybrid mongrel singular finite element and the mixed method of contact to investigate the effect of crack closure on the stress intensity factors of cracked bending plates. The influence of crack closure on the stress intensity factors are analyzed in two cases. 1) line contact : employing two dimensional model for a single edge cracked plate loaded by tensile stress and bending moment. 2) Area contact : employing 3-D model for a plate subjected to bending with a crack going through the thickness of the plates. Some numerical tests proves this approach is in accordance with known solution in spite of quite a coarse mesh.
Modification of Analytical Model for the Low-Velocity Impact Detection Using Piezopolymer Sensor Signals
김인걸 ; 정석모 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 70~70
An experimental and theoretical study was performed to demonstrate the feasibility of using piezopolymer thin film sensor(PVDF) to detect and monitor low-velocity impact event. The work was then extended to include numerical and experimental investigation into the use of short circuit voltage of PVDF sensor without using charge amplifier to detect low-velocity impact. The relationship between the contact force and the signals of the attached strain gage and PVDF sensor to the isotropic beam subjected to low-velocity impact are derived by using Rayleigh-Ritz method and piezoelectric constitutive equation. The relation for the open circuit and short circuit voltage of PVDF sensor is derived based on the equivalent circuit model of the piezoelectric sensor. The natural frequencies and damping ratio of the specimen obtained from the vibration test are used to modify the analytical model and therefore the difference between measured and simulated signal of the modified analytical model in both forward and backward problem are considerably reduced.
Sampling Time Selection for Design of Digital Flight Control System
하철근 ; 류승완 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 77~77
In this paper, an issue of sampling time selection for design of digital flight control systems, in which the plant to be controlled with model uncertainty includes a flexible structural vibration mode, is treated. To examine how to select a proper sampling time for the digital normal acceleration CAS design, the optima LQG design method is adopted. This study is conducted according to evaluating effect of sampling time on design of the digital CAS, which is obtained in the process of discretization of the LQG CAS designed for the design specifications to be satisfied. As results, it is told that sampling time would be properly determined under consideration of a type of unexpected command coming into the system, characteristics of process and measurement noises, RMS of state variables, and model uncertainty.
Peak-seeking Controller Design for Formation Flight of an Unmanned Aerial Vehicle
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 87~87
In this paper, a peak-seeking controller is proposed to reduce the energy consumption in a formation flight. The nonlinear system is considered because the induced lift experienced by the trailing aircragt in formation is an unknown static nonlinear function with a maximum value. The proposed controller consists of the estimation part using a Kalman filter and the control part for tracking the sinusoidal input. The Kalman filter estimates the gradient of this function to find the set point that maximizes the output. The modified LQR(Linear Quadratic Regulator) is used to effectively track the bias and high frequency sinusoidal input. Simulation results show that the maximal point, corresponding to the mean value, of the Gaussian function can be found, and the optimal vehicle position can be maintained by using the proposed controller. Therefore this scheme, using modern estimation techniques, can be used to design the peak-seeking controller in an optimal sense, even though the output function is not smooth.
The Analysis of Radiative Heat Transfer on the Unsteady Combustion of Solid Propellant during pressurization
정호걸 ; 이창진 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 94~94
In this study, the numerical calculation for the effect of radiant heat feedback on the unsteady burning of solid propellant for pressurizing the combustion chamber was conducted. The chemical reaction in the condensed phase was considered as a surface reaction within the very thin layer adjacent to the propellant surface and αβγ flame model was used to evaluate the heat distribution in the gas phase. Two-flux model was used for radiant transfer equation. The spatial distribution of diameter and volume fraction of Al, Al₂O₃ which play a important role in determining the coefficients related to radiation were obtained using unsteady combustion-flow model. The energy equation and radiant transfer equation in the gas phase were decoupled. Numerical results indicate that the unsteady burning rate of solid propellant strongly depends on the ratio of condensed phase time scale(
) to transient pressure time scale(
is O(100), the burning rate shows a nonlinear behavior. The burning rate increases as the increase of radiation and the effect of radiant heat flux only appears as a dominant factor at the initial stage of pressurization.
Study on the Partially Premixed Flame Structure of Supersonic Hydrogen Diffusion Flame Using Mixing Simulation and OH PLIF
김지호 ; 김제홍 ; 박철웅 ; 한재원 ; 윤영빈 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 101~101
Experiments have been performed to investigate the structure of axisymmetric hydrogen diffusion flame with a supersonic coflowing air. The characteristics and inner structures of supersonic flame and subsonic flame were investigated through the process of increasing the coflow air velocity from subsonic to supersonic(M=1.8) with the fuel velocity fixed to mach 1. The subsonic and the supersonic flow field are compared and analyzed by the CFD for the non-reacting conditions, and these are compared with the distribution of OH radical of each flame obtained by the PLIF method. As the coflowing air velocity is changed from subsonic to supersonic, H₂-air turbulence flame shows the characterisitics of partially premixed flame, and strong reaction zone that is indicated by intense OH signal is found in the center which is different from subsonic flame case. The CFD results show that the fuel jet is blocked by the high pressure zone formed downstream of the fuel nozzle and therby the loss of jet momentum is incurred. Hence, the fuel jet passes along the recirculation zones behind the bluff-body fuel nozzle and experience relatively long mixing time, which is believed to be the cause of the partially premixed flame characteristics found in the present supersonic flames.
An Experimental Study on Decelerating Parachutes
오세윤 ; 박정기 ; 이종건 ; 안승기 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 110~110
This paper describes the testing carried out on the decelerating parachute models, the test techniques developed for the testing, and the lessons learned. Tests were carried out to determine the aerodynamic characteristics of the parachutes such as drag and lift through out the speed range of 10 to 60 m/s and the stability coefficients at incidences of up to 20°. The testing approach described in this paper can be applied to the wind tunnel testing for the future parachute development program.
The Conceptual Design of Air-Launching Micro Space Launcher, Mirinae-1
이재우 ; 황진용 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 117~117
Air-launch, which can reduce the launching cost and has no restriction on the selection of launching sites, is implemented to the design of the micro-rocket for launching the nanosat to LEO. In this study, the conceptual design was performed for the three stage air-launching rocket, which can be launched from the F-4E. The rocket consists of liquid-solid-solid rocket engines, and can launch the payload of 2kg. The first stage is LRM of LOX/Kerosene and the second/third stages are SRM of HTPB/AP/AP. The rocket is launched at the altitude of 11~12 km from Phantom(F-4E) that flies at Mach 0.85. The first stage separation is achieved at 31km and the second stage/nose fairing separation occurs at 62 km. By air-launching considerable amount of the propellant can be reduced, which results in the reduction of the total size of the rocket. The feasibility of the installation to F-3E was confirmed and the feasibility of the practical development was reviewed by building the one-third scale mock-up.
Feasibility Study of Satellite Simulatior Development by Using Multithreading and Shared Memory
이상욱 ; 권오룡 ; 이호진 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 125~125
A feasibility study for development of satellite simulator using multithreading and shared memory on Windows NT Server as operating system is described. A byte-ordering problem, which was occurred when the simulator for KOMPSAT-1 was developed on HP workstation, was resolved. And, a utilization of shared memory and moultithread improved degradation due to frequent inter-process communication of multipocess simulator. A real-time scheduling was implemented by using scheduling function on Windows NT and its functioning was satisfactory.
LTA (Lifter-Than-Air) Systems - revisited
염찬홍 ; 유혁 ; 임철호 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 132~132
Balloons have been utilized mostly as scientific purposes fince their effectiveness were proven. However, with the use of advanced materials and other hi0tech system technologies, they are also welcomed in various sporting purposes nowadays. Even advanced research institutes such as NASA or CNES are also investigating the possibilities of LTA system as scientific research tools in other planets. In earth atmosphere, here can play some important roles including as platforms for telecommunication relay and earth observing system. In this paper, their technical aspects and some advanced researches undergoing by NASA are briefly reviewed.
The Structure and Materials of Airship
강왕구 ; 김동민 ; 이진우 ; 염찬홍 ; 임철호 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 141~141
In this paper, the flight mechanism, the structure and characteristic of blimp, rigid airship and semi-rigid airship are described. Each component of airship-envelop, ballonet, tail units, gondola and engine- are introduced. The development of light envelop material is one of the key technology to build airships successfully. The structural requirements and layer sequence of airship envelop are specified and materials of each layer are compared. The strength and weight requirements for airship are specified. Also, the manufactureability and maintainability.
The History of Airship and The New Concept Airships
강완구 ; 김동민 ; 김현경 ; 이해창 ; 염찬홍 ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 29, issue 2, 2001, Pages 152~152
The paper describes the history of airship from the 18th century and examines the possibility and potential of new concept and high tech airships in the 21st century. The paper deals the success and failure of early pioneers, the golden age of airship by zeppelin, the tragedy of Hindenburg and following collapse of airship industry. The new concept airships, which are hybrid between the most nature friendly, accident safe airship and the technology of aerospace and other leading edge technologies, can overcome the shortcoming of conventional airplane and maximize the potential of airships. The paper introduces several new concept airships, related industry and the new technologies which are essential to develop new concept airships.