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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 26, Issue 3 - May 1998
Volume 26, Issue 1 - Feb 1998
Volume 26, Issue 8 - 00 1998
Volume 26, Issue 7 - 00 1998
Volume 26, Issue 6 - 00 1998
Volume 26, Issue 5 - 00 1998
Volume 26, Issue 4 - 00 1998
Volume 26, Issue 2 - 00 1998
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Flow Fields Interaction Between Drooped Intake, Fan and Downstream Engine Component in Civil Turbofan Engines
Joo, Won-Gu ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 1~1
A three dimensional numerical computational method using actuator disk blade row model is applied to the problems of calculating the asymmetric performance of a turbofan due to the three dimensional nature of the intake and due to the presence of the engine pylon and the core engine in high bypass ratio civil turbofan engines. Good agreement between prediction and experimental results is demonstrated. The relative importance of the intake asymmetry and the pylon and the core engine is discussed.
Experimental Manipulation of the Boundary Layer of the Airfoil with Slit Suctions and Riblets
Park, Kye-Hyang ; Yoo, Sang-Sin ; Lee, Bong-Joon ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 9~9
An experimental study on manipulation of the boundary layer of the two-dimensional NACA 0024 wing with slit suctions and riblets is presented. The slit locations, the number of slits, Reynolds number, angle of attack and the suction rate coefficient are variables. Experimental results far the lift and drag coefficients of the two dimensional wing with slit suctions and riblets are presented. When the slit suction is applied on the wing wall the lift and drag coefficients increase. Wing model with round riblets on the wall shows an increase of the lift coefficients and a decrease of the drag coefficient. When the suction slits are installed on the upper wall of the wing and riblets around the wing the boundary layers of the wing are manipulated favorably.
A Study on Optimal Design of Airfoils
Yu, Chung-Keun ; Kwon, Jang-Hyuk ; Sung, Chun-Ho ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 18~18
A computer program to design an optimal shape of airfoil is developed. It is based on a computationally efficient Euler solver with a numerical optimization algorithm. The design goal in the present study is to obtain the airfoil geometry which produces the minimum possible wave drag while maintaining the lift at a specified design condition. To do this, the drag coeffient is used as the objective function and the design sensitivity is obtained by finite-difference method. Finally, airfoil designs for the transonic flow condition are performed with various shape functions and the comparison of the results is presented.
Passive Control of Condensation Shock Wave on a Wall Mounted Airfoil in Transonic Speed
Kwon, Soon-Bum ; Choi, Young-Sang ; Jeon, Heung-Kyun ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 25~25
Tests were made on the NACA 0012 airfoil model in a
transonic wind tunnel of the free stream Mach number of 0.75 to evaluate the effects of cavity size on passive condensation shock wave/boundary layer control. The static pressure distributions and Schlieren photographs for the transonic flow over a porous surface airfoil are presented and compared with the results fur the solid surface airfoil. It was turned out that the present passive control weakens the condensation shock wave and reduce the pressure rise across the shock wave. The normal condensation shock wave for solid surface was changed to the pressure disturbances due to the effects of passive control. The result also showed that wider porous area for the same porosity is more effective than the cases of its opposite.
Computation of Shock-Turbulent Boundary Layer Interaction Flow with One-Equation Turbulence Models
Kim, Min-Hwan ; Park, Seung-O ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 36~36
The performance of one-equation turbulence models of Baldwin-Barth and Spalart-Allmaras is assessed against shock-turbulent boundary layer interaction now. The flow configurations are the 20 degree compression ramp flow and the axisymmetric bump flow. The Baldwin-Lomax, Baldwin-Barth, and Spalart-Allmaras models have been implemented into the compressible Navier-Stokdes code. Modification of the Baldwin-Earth model for non-equilibrium turbulenct flow is suggested. Computational results indicate that the model modification yielded substantially improved solution.
Nonlinear Five-Mode Interactions in a Free Shear Layer
Seo, Tae-Won ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 45~45
In this study to investigate the role of energy interaction mechanism between the wave modes the large-scale structures are decomposed into 3 fundamentals and 2 subharmonics and the integral energy method hag been used. It is found that the effect of the spanwise phase angle
on the evolution of the wave modes and the shear layer far downstream where the subharmonics become dominant can be considerable. It is also found that the presence of the three-dimensional modes may contribute to increases or decreases of the shear layer growth depending on the values of
that control the nonlinear mode interactions and consequently can either enhance or attenuate entrainment and mixing.
Stability Analysis of Wakes with Density Gradient
Sin, Dong-Sin ; Hong, Seong-Je ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 53~53
This paper investigates the linear stability of wakes with special emphasis on the difference of velocity and density. Velocity and density profiles for laminar flows have gaussian profiles. Incompressible wakes have two generalized inflection points and two unstable modes-sinuous and varicose modes. Sinuous modes are more unstable than varicose modes irrespective of density variation, which shows wakes will be destabilized by sinuous modes. Large velocity difference and density difference lead to more unstable wakes due to large momentum difference. Contours of typical flow variables show that baroclinic term is more important than dilatational term in the development of vorticies.
Delamination Detection in Composite Beams Using Neural Networks
Seong, Dae-Un ; Ju, Sang-Geon ; Kim, Cheon-Gon ; Hong, Chang-Seon ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 62~62
An important aspect of the concept of smart structures is the automated structural health monitoring of the structure. This paper presents a new approach to detect the damage in composite structures and applications of artificial neural networks in the damage identification. The approach is based on the neural network to deduce the damage size and location from the change of structural dynamic properties. A neural network is trained with the natural frequencies of the first-five modes obtained from finite element analyses of composite beams with various delaminations. The effectiveness of neural networks trained by various properties was discussed for determining the location and size of any delaminations.
An Experimental Study on Fatigue Crack Growth of Cold-Expanded and Ring-Indented Holes on Both Sides
Song, Jeong-Hun ; Yu, Jin-Sang ; Im, Won-Gyun ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 72~72
In this investigation, we explore a new method fer the retardation of fatigue crack growth, using ring-indentation on both sides around the fastener hole combined with cold-expansion of holes. Residual stresses at the vicinity of a hole are evaluated using a fracture mechanic approach. The results of this method are compared with those of simple cold-expansion alone. The motivation is to develope a simple and effective method far obtaining a significant increase in fatigue lives to total failure compared with that from cold-expanded hole alone. Fatigue testing of aluminum specimen showed that the fatigue crack retardations are observed after the application of the method, and the retardation effect is, indeed, far greater than that obtained with cold-expansion alone.
Transient Response and Sensitivity of Multiple Degree of Freedom Structural Dynamic Systems using Time Finite Element Method
Park, Sung-Ho ; Kim, Seung-Jo ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 79~79
A bilinear formulation is used far developing the time finite element method (TFM) to obtain transient responses of both linear, nonlinear, damped and undamped systems. In TFM, time is discretized in a number of finite elements and the response history over each element is expressed in terms of basis functions in the time coordinate. Also the formulation, used in the h-, p- and hp-versions, is extended and found to be readily amenable to multi-degree-of-freedom systems. An advantage of the TFM is the ease with which one can calculate the sensitivity of the transient response with respect to various design parameters, a key requirement fer gradient-based parameter identification schemes. The method is simple, since one obtains the sensitivities of the response to design parameters by differentiating the algebraic equations, not original differential equations. Mostly, the results were obtained using the Legendre polynomials as basis functions, though, in some cases other orthogonal polynomials namely, the Hermite, the Chebyshev, and integrated Legendre polynomials were also employed.
Study on the Delamination Buckling Behavior by Use of Shadow-moire Method
An, Jin-Su ; Gyeong, U-Min ; Kim, Cheon-Gon ; Hong, Chang-Seon ; Jeon, Seung-Mun ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 86~86
Out of plane displacement was measured by the shadow moire method combined with digital image processing for composite laminates subjected to compressive loading with through-the-width delamination. In the experiments, experimental setup was constructed for accurate measurement of the parameters for shadow moire. For the processing of the moire fringe pattern, the image processing program was developed by the following algorithm. First, the moire fringe was sharpened using peak-detection method. Second, the order of fringe was given to the sharpened fringe, and the fringe that has the same order was recognized through grouping procedure. Then the out of plane displacement nab obtained. The out of plane displacement of whole field of specimen was measured when buckling was occurred. The experimental results were compared with those of finite element analysis. In the finite element analysis, the eight-node degenerated shell element was used and the contact between laminates was considered using beam element. The results of experiment and finite element analysis show good agreement.
On the Approximate Solution of Nonclassically Damped Linear Systems under Random Excitations
Hwang, Jai-Hyuk ; Kim, Doo-Man ; Yoo, Byung-Sung ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 96~96
Nonclassically damping comes from drastic variations of energy absorption rates of the materials in different parts of structures, or from the external damping sources inserted into the structures. In this study, an approximate method based on the real valued normal modes to analyze the responses of a nonclassically damped system under stationary random excitations has been suggested. The dynamic responses of a aircraft landing gear under stationary random excitations has been analyzed using the proposed method. It has been found by a series of simulation that this method is superior to other approaches in respect of computational effort and accuracy.
Predictor-Corrector Procedure for Accurate Recovery of Stresses and Displacements in Multilayered Composite Panels
Park, Jin-Woo ; Kim, Yong-Hyup ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 104~104
A post-processing procedure is presented for the accurate recovery of stresses and displacements in multilayered composite panels subjected to mechanical and thermal loads. The finite element model used in conjunction with the present procedure is an 18-node degenerate solid model based on the Hellinger-Reissner variational principle. The post-processing procedure can be conveniently divided into two phases. In the first phase, the predictor phase, thickness distribution of inplane stresses and their derivatives with respect to the inplane axes, are evaluated using the Zienkiewicz-Zhu superconvergent patch recovery technique. Thickness distribution of the transverse stresses are evaluated by piecewise integration of the three-dimensional stress equilibrium equations, in the thickness direction. The second phase, the corrector phase, consists of series of procedures based on the stress-strain relationships, the strain-displacement relationships and piecewise integration of the three-dimensional stress equilibrium equations, in which, accuracy of the displacements and the stresses are enhanced using the transverse shear stresses obtained from the predictor and the displacements obtained from the finite element analysis. The effectiveness of the proposed computational procedure is demonstrated by means of numerical examples of composite panels subjected to mechanical and thermal loads. The numerical results are compared with the exact solutions of the three-dimensional thermoelasticity equations to demonstrate the accuracy of the proposed procedure.
Combustion Behavior of Solid Rocket Motor Embedding Silver Wire in Propellant
Hyun, Hyung-Soo ; Hwang, Kab-Sung ; Yim, Yoo-Jin ; Kim, Chang-Kee ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 115~115
The combustion effect of metal wire on solid rocket motor was investigated by static firing test of small motor charged with HTPB/AP propellant embedded with silver wires. It was found that the burning surface area in steady state region was not affected by the number of wires but at the beginning of combustion, more number of wires made time to reach at constant burning area and pressure shorter. The strand burning rate of propellant embedded with silver wire was shown to be consistent with that obtained from small motor firing test and to be largely dependent on the coating material which was useful far the bonding metal wire and propellant.
3-D Stochastic Simulation of Turbulent Premixed Flames in a Closed Vessel
Kwon, Se-Jin ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 123~123
A numerical thechnique to simulate the three dimensional propagation of turbulent premixed flames is presented. The objective is to further develop the existing two dimensional method and test the validity of the resulting technique in predicting the propagation speed and geometric structure of the flame. The approach uses time-series simulation of the unburned gas turbulence properties, such as mean velocity field, turbulence intensities, spatial and temporal correlations of velocity fluctuations. Influence of approaching flame on these properties were neglected. The dynamic behavior of the flame front was described by solving G-equation in an instantaneoulsly simulated turbulent flow field. Predictions were compared with existing experimental data and two dimensional simulations of hydrogen/air premixed flames with various turbulence intensities in a closed vessel. Three dimensional time dependent simulation resulted in correct trends of the measured flame data with increased accuracy compared with two dimensional simulation. Comparisons were made in flame radius growth rate, rms flame radius fluctuations, and average perimeter and fractal dimensions of the flame boundaries. The reasonable behavior and high efficiency proves the usefulness of this method in practical problems of flame propagation.
System Identification of a Single Turbo-Prop Aircraft Dynamic Model for Flight Simulation
Lee, Hwan ; Lee, Sang-Kee ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 131~131
The aerodynamic derivatives of a single turbo-prop aircraft at a specified flight condition for the best deduction of the dynamic characteristics are estimated by using the modified maximum likelihood estimation method which is known to be unbiased, efficient, and consistent. The flight test data, necessary to the estimation of aerodynamic derivatives, is obtained by implementing the six degree of freedom nonlinear flight simulation to consider the effects of several control input types, control deflection amplitudes, and intensity of turbulence. The simulated data is added with the measurement noise, which is regarded as the actual flight test data. The 6-DOF nonlinear equation is algebraically linearized so that the linear state equation contains aerodynamic derivatives in a state-space term. This linear state equation is used in the maximum likelihood method. The aerodynamic derivatives are estimated by considering the effects of input types, deflection amplitude, turbulence intensity, and measurement noise, and quantitative analysis of the results is followed and discussed.
Performance Analysis of Four Attitude Determination Methods using Line of Sight Vectors
Park, Keun-Joo ; Kim, Jin-Ho ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 140~140
The objective of attitude determination system(ADS) is to determine the correct direction of the spacecraft relative to either an inertial reference frame or LVLH frame. In this paper, four algorithms are presented for determining three-axis attitude from two or more vector observations. The first of these, the TRIAD algorithm provides a deterministic solution for the attitude based on two vector observations. The second, the optimized TRIAD, yields a matrix which is better than either one of the two matrices in that it is the closest to the correct matrix. The third, the Q-method, is an optimal algorithm which determines the attitude that achieves the best weighted overlap of an arbitrary number of reference and observation vectors. The fourth, the FOAM algorithm, determines the optimal matrix directly. By computing the standard deviations and the attitude errors of the four algorithms using a fairly realistic observation model for the measurement errors, the attitude determination performance of the four algorithms are compared and their relative merits are discussed.
Robust Stability Condition for Reduced-Order Controller
Sun, Byung-Chan ; Tahk, Min-Jea ;
Journal of the Korean Society for Aeronautical & Space Sciences, volume 26, issue 3, 1998, Pages 148~148
This paper deals with the robust stability condition of the closed-loop system with a low-order-controller which is obtained via balanced truncation for an originally designed high-order controller. It is assumed that controller reduction error and plant's uncertainty are represented by using coprime matrix fractions. The stability condition is derived from the small gain theorem. It is shown that the resulting robust stability condition is better than known results. As a special case, the nominal stability condition far the low-order controller is also dealt with.