• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.458-464
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• 2011

A new method identifies coupled fluid-structure system with a reduced set of state variables is presented. Assuming that the structural model is known a priori either from an analysis or a test and using linear transformations between structural and aeroelastic states, it is possible to deduce aerodynamic information from sampled time histories of the aeroelastic system. More specifically given a finite set of structural modes the method extracts generalized aerodynamic force matrix corresponding to these mode shapes. Once the aerodynamic forces are known, an aeroelastic reduced-order model can be constructed in discrete-time, state-space format by coupling the structural model and the aerodynamic system. The resulting reduced-order model is suitable for constant Mach, varying density analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.20-24
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• 2011

In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.218-224
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• 2011

A supersonic inlet at angle of attack has anti-symmetric pressure distribution, and it can make flow instability and structural problem. In this study, numerical analysis of three-dimensional inviscid flow was conducted under various throttle ratio and angle of attack conditions. Throttle ratio was defined as the ratio of the exit area to the smallest cross section area at inlet, and the ratio is controlled from 0 to 2.42. At various angle of attack, the characteristics of steady and unsteady flow around supersonic inlet is observed under different throttling ratios. From these results, pressure recovery curves and pressure history curves were plotted by post processing. Using pressure history data, FFT analysis is also carried out. Through these processes, it shows the tendency of pressure distribution anti-symmetricity and changing dominant frequency as increasing angle of attack.

• 한국전산유체공학회지
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• 제14권3호
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• pp.33-48
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• 2009

In the present study, a fast grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were also simulated to demonstrate the robustness of the present grid deformation technique.

• 대한기계학회논문집B
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• 제20권12호
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• pp.3960-3969
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• 1996

A fluid flow inside a circular cylinder subject to horizontal and circular oscillation is analyzed theoretically. Under the assumption of small-amplitude oscillation, the governing equations take linear forms. The velocity field is obtained in terms of the first kind of Bessel function of order 1. It was found that a particle describes an orbit close to a circle in the central region and an arc near the side wall. We also obtained the Stokes' drift velocity induced by the traveling wave along the circumferential direction. The Eulerian streaming velocities at the edge of the bottom and side boundary layers were also obtained. It was shown that the vertical component of the steady streaming velocity on the side wall is almost proportional to the amplitude of the free surface motion.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.190-201
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• 1998

The numerical methodology for computing the impact forces of the water entry bodies has been developed. The present method assumed the impact occurs within a very short time interval and the viscous effects do not have time enough to play a significant role in the impact forces, that is, the flow around a water-entry object was assumed as an inviscid potential flow and is solved by the source panel method. The elements fully submerged into the water are routinely treated, but the elements intersected with the effective planar free surface are redefined and reorganized to be amendable to the source panel method. To validate the present code, it has been applied to disk and ogive model and compared with experimental data. Good agreement has been obtained.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.177-181
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• 2007

Present study examines the numerical issues of cell structure simulation for various regimes of detonation phenomena ranging from weakly unstable to highly unstable detonations. Inviscid fluid dynamics equations with $variable-{\gamma}$ formulation and one-step Arrhenius reaction model are solved by a MUSCL-type TVD scheme and 4th order accurate Runge-Kutta time integration scheme. A series of numerical studies are carried out for the different regimes of the detonation phenomena to investigate the computational requirements for the simulation of the detonation wave cell structure by varying the reaction constants and grid resolutions. The computational results are investigated by comparing the solution of steady ZND structure to draw out the minimum grid resolutions and the size of the computational domain for the capturing cell structures of the different regimes of the detonation phenomena.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.643-651
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• 1998

Turbulent unsteady flows in the entrance region of a square duct are investigated with a hot-wire anemometer system. The velocity waveforms the mean and turbulence components of the axial velocity and the entrance length are obtained as a major characteristics of the developing turbulent unsteady flows. An inviscid flow theory is presented to describe the developing axial mean velocity profiles. A good agreement is seen between the measured and theoretically predicted values. The propagation of turbulence generated near the entrance of the square duct is satisfactorily approximated by an empirical correlation of the propagation of turbulence proposed so far. The local turbulence intensi-ty is found to be a little smaller in the accelerating phase than in the decelerating phase. The entrance length is about 60 times as large the hydraulic diameter.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.887-892
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• 2003

A front-end cooling fan is designed and tested in the present study. The design technique is developed using the one-dimensional inviscid flow through the fan blade, the empirical equations, and the experimental correlations. Design data for the blade can be obtained for a given flow rate and a pressure rise. A parabolic function is used to generate a sweep of the fan. Characteristics of the blade geometry are discussed between the huh and the tip. The fan is tested in the fan test unit. The measured volume flow rate at the operating point is in good agreement with that of the design specifications. Sound pressure levels of the noise are predicted with the Ffowcs Williams-Hawkings equations. Calculation results of the sound pressure level(SPL) 1m away from the fan are obtained and cpmpared with the measured data.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.384-390
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• 2005

A automobile front-end cooling fan are designed and tested in the present study. The design technique is developed using the one-dimensional inviscid flow through the fan blade, the empirical equations, and the performance prediction models. Numerical calculations of the three-dimensional turbulent flow around the designed cooling fan are carried out. Flow characteristics and pressure distributions on the pressure and suction side of the fan are investigated. Performance test results of the total pressure and flow rate are presented.