• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.532-540
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• 2008

Recently there are growing interests in calculating aerodynamic characteristics of aircraft configurations with structural deformation using the FSI(Fluid-Structure Interaction) system in which CFD(Computational Fluid Dynamics) and CSD(Computational Structure Dynamics) modules are coupled. In this paper the FSI system comprised of CAD, CFD, CSD, VSI(Volume Spline Interpolation) and grid deformation modules was constructed in order to investigate aerodynamic characteristics of the deformed shape. In the process VSI and grid generation modules are developed to combine CSD and CFD routines and to regenerate the aerodynamic grids for the deformed shape, respectively. For the CFD and CSD analysis, commercial programs FLUENT and NASTRAN were used. As a test model, DLR-F4 wing configuration was chosen and its aerodynamic characteristics were calculated by applying the static FSI system. It was shown that lift and drag coefficients of the wing at mach number 0.75 are reduced to 20.26% and 18.5%, respectively, owing to the structural deformation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.984-991
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• 2009

In this study, transonic aeroelastic response analyses have been conducted for the DLR-F4(wing-body) aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.7
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• pp.489-498
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• 2019

The airloads and structural loads of Light Civil Helicopter (LCH) rotor are investigated using a loose CFD/CSD coupling. The structural dynamics model for LCH 5-bladed rotor cwith elastomeric bearing and inter-bladed damper is constructed using CAMRAD-II. Either isolated rotor or rotor-fuselage model is used to identify the effect of the fuselage on the aeromechanics behavior at a cruise speed of 0.28. The fuselage effect is shown to be marginal on the aeromechanics predictions of LCH rotor, though the effect can be non-negligible for the tail structure due to the prevailing root vortices strengthened by the fuselage upwash. A lifting-line based comprehensive analysis is also conducted to verify the CFD/CSD coupled analysis. The comparison study shows that the comprehensive analysis predictions are generally in good agreements with CFD/CSD coupled results. However, the predicted comprehensive analysis results underestimate peak-to-peak values of blade section airloads and elastic motions due to the limitation of unsteady aerodynamic predictions. Particularly, significant discrepancies appear in the structural loads with apparent phase differences.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.72-78
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• 2008

In this study, advanced (fluid-structure interaction (FSI)) analysis system has been developed in order to predict turbine cascade performance with blade deformation effect due to aerodynamic loads. Intereference effects due to the relative movement of the rotor cascade with respect to the stator cascade are also considered. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation k-ω SST turbulence models are solved to accurately predict fluid dynamic loads considering flow separation effects. A fully implicit time marching scheme based on the (coupled Newmark time-integration method) with high artificial damping is efficiently used to compute the complex fluid-structure interaction problem. Predicted aerodynamic performance considering structural deformation effect of the blade shows somewhat different results compared to the case of rigid blade model. Cascade performance evaluations for different elastic axis positions are importantly presented and its aeroelastic effects are investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.83-92
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• 2007

There are many numerical methods to solve large-scale fluid-structure interaction(FSI) problems. However, these methods require very fine mesh to achieve the reasonable numerical accuracy and stability due to the concentrated and volatile hydrodynamic pressure caused by the liquid sloshing. Consequently, the numerical analysis targeting for the long-period time response with the desired numerical accuracy Is very highly time-consuming. The aim of this paper is to suggest a new method to analyze the hydroelastic behavior of the LNGC containment by using the global-local numerical approach. The reliability of the presented method is firstly examined, and then its efficiency is demonstrated by presenting that the long-period local responses of the LNGC containment are obtained with relatively short CPU time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.31-36
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• 2006

In this study, nonlinear static aeroelastic analysis system for a high-aspect-ratio wing are developed using the transonic small disturbance (TSD) and large deflection beam theory and validated. For the coupling between fluid and structure, the transformation of displacement from the structural mesh to aerodynamic one is performed by the shape function of the beam finite element and the inverse transformation of force by work equivalent load concept. Also, for the static aeroelastic analysis of the wing the use of TSD aerodynamics are justified. The validation of the system includes one of the efficient transformation methods of force and displacement.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.433-441
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• 2009

Generally, the events in nature have multi-disciplinary characteristics. To solve this problems, these days loosely coupled methods are widely applied because of advantage of solvers which are already developed and well proved. Those solvers use different mesh system, so transformation and mapping of data are vital in the field of fluid-structure interaction(FSI). In this paper, the interpolation of deformation which is used globally and compactly supported radial basis functions(RBF), and mapping of force which use principle of virtual work are examined for computing time and accuracy to compare ability with simple 3-D problem. As the results, interpolation scheme of compactly supported radial basis functions are useful to interpolation and mapping for large-scale airplane in FSI with a k-dimensional tree(kd-tree) which is a space-partitioning data structure for organizing points in a k-dimensional space.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.21-27
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• 2003

In general, simple fluid added mass method is used for the seismic and vibration analysis of the immersed structure to consider the fluid-structure interaction effect. Actually, the structural response of the immersed structure can be affected by both the fluid added mass and damping caused by the fluid viscosity. These variables appeared as a consistent matrix form with the coupling terms. In this paper, finite element formula for the inviscid fluid case and viscous fluid case are derived from the linearized Navier Stoke's equations. Using the finite element program developed in this paper, the analyses of fluid added mass and damping for the hexagon core structure of the liquid metal reactor are carried out to investigate the effect of fluid viscosity with variation of the fluid gap and Reynolds number. From the analysis results, it is verified that the viscosity significantly affects the fluid added mass and damping as the fluid gap size decrease. From the analysis results of eccentricity effect on the fluid added mass and damping of the concentric cylinders, the fluid added mass increase as the eccentricity increases, however the fluid damping increases only when the eccentricity is very severe.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.295-302
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• 2006

In this study, computational structural dynamic analyses of a gyrocopter have been conducted considering unsteady dynamic hub-loads due to rotating blades. 3D CATIA models with detailed mechanical parts we constructed and virtually assembled into the complete aircraft configuration. The dynamic loading generated by rotating blades in the forward flight condition are calculated by a commercial computational fluid dynamics (CFD) code such as FLUENT. Modal based transient and frequency response analyses are used to efficiently investigate vibration characteristics of the gyrocopter. Free vibration analysis results for different fuel and pilot conditions, frequency responses and transient responses for critical flight conditions are also presented in detail.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.519-522
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• 2010

Flow-induced vibration analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics has been developed in order to investigate detailed dynamic responses of designed compressor blades. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.