• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.155-174
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• 2006

Parabolized stability equations for compressible flows in general curvilinear coordinate system are derived to deal with a broad range of transition prediction problems on complex geometry. A highly accurate finite difference PSE code has been developed using an implicit marching procedure. Compressible and incompressible flat plate flow stability under two-dimensional and three¬dimensional disturbances has been investigated to test the present code. Results of the present computation are found to be in good agreement with the multiple scale analysis and DNS data. Stability calculation results by the present PSE code for compressible boundary layer at Mach numbers ranging from 0.02 to 1.5 are also presented and are again seen to be as accurate as the spectral method.

• Bulletin of the Society of Naval Architects of Korea
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• v.14 no.4
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• pp.3-14
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• 1977

There are many Beam-Column connections in general structures and ship structures. For simplicity and convenience of analysis, the connections are mostly considered hinged when not reinforced or rigidly fixed when reinforced. This paper has intended to analyze the Beam-Column connection which is assumed two dimensional flat plate. The analysis has been preformed by Finite Element Method following the change of moment of inertia at connection. The conclusion of this investigation is as follows: By reinforcing or increasing the moment of inertia at connection part, the stress distribution of whole structure and the stress concentration at that part are relieved. Displacements of beam(when column is fixed) are almost linearly decreasing by the change of moment of inertia at connection.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.110-119
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• 2006

An accurate and cost efficient method PSE is used for the stability analysis of 2D or 3D compressible boundary layers. A highly accurate finite difference PSE code has been developed at a general curvilinear coordinate system using an implicit marching procedure to deal with a broad range of transition predictions problems. Evolution of disturbances in compressible flat plate boundary layers are studied for free-stream Mach numbers ranging from 0 to 1.5. The effect of mean-flow nonparallelism is found to be weak on two dimensional waves and strong on three dimensional waves. The maximum amplification rate increases monotonically with Mach number. The present PSE solutions are compared with previous numerical investigations and experimental results and are found to be in good agreement.

• Journal of KSNVE
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• v.6 no.1
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• pp.97-106
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• 1996

This paper presents systematic study of the experimental application of a free-interfaced component mode synthesis method. In the free-interfaced component mode synthesis method, an error the to truncated higher modes and neglected ineria loadings on a component from the connected component is inherent. Also, it is difficult to directly use experimental modal data in a modal synthesis method which links experimental model to finite-element model because of many inconsistencies between experimentally obtained and analytically obtained modal vectors and missing degrees-of-freedom (DOFs) such as rotational DOFs. In order to solve these problems, three methods, the first one based on attaching auxiliary weights to the connection points, the second one utillizing the normalization of experimental modal vector, and the third one generating smoothed and expanded experimental mode shapes, are studied in this paper. Finally, the study is illustrated for a flat-plate structure by using simulated and measured experimental data.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.19-26
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• 1991

The complete, fully-elliptic Reynolds-averaged Navier-Stokes equations have been solved using a two-layer model, in the $\kappa-\varepsilon$ turbulence model, for the axisymmetric body. Numerically generated boundary-fitted coordinate system and the finite analytic methods are used to solve the governing equations. Calculations are started after the middle body with given inlet conditions. The velocities and the turbulent quantities at the inlet section are specified by solving the boundary layer equations or by standard flat-plate boundary profiles. The effects of the inlet conditions on the solution are investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.45-51
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• 2002

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle 8 DOFs truck model and a 5-axle 13 DOFs semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. Although the noise produced by the bridge vibration is not serious in itself, which is below the audible frequency range, it should be considered as an interaction problem between vehicle noise and bridge vibration noise in order to evaluate the traffic noise around the bridge.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.90-97
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• 1999

An implicit turbulent flow solver is developed for 2-D unstructured hybrid meshes. Spatial discretization is accomplished by a cell-centered finite volume formulation using an upwind flux differencing. Time is advanced by an implicit backward Euler time stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one equation model, which is coupled with wall function. The numerical method is applied for flows on a flat plate, the NACA 0012 airfoil, and the Douglas 3 element airfoil. The results are compared with experimental data.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2782-2787
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• 2008

The subcavity passive control technique is used in present study. Cavity-induced pressure oscillation has been investigated numerically for a supersonic three-dimensional flow over rectangular cavities at Mach number 1.83 at the cavity entrance. Time dependent supersonic turbulent flow over cavity were examined by using the three-dimensional, mass-averaged Navier-Stokes equations based on a finite volume scheme and large eddy simulation. The results showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate.

• Journal of Hydrospace Technology
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• v.2 no.2
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• pp.14-23
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• 1996

The Reynolds-averaged Navier-Stokes equations for turbulent flow around a two-dimensional foil section moving ova. a flat surface (roller plate) is solved. The numerical method utilized the finite-difference schemes in collocated grids and the Baldwin-Lomax model is employed for turbulence closure. Calculations are carried out for three foil sections of different mean-line shape with various height ratio. As a foil approaches the bottom surface, the lift is augmented, while there exist some differences in pitching moment due to mean-line shape. It was found that the S-shaped mean line deteriorates lift characteristics but increases pitching moment to restore the designed height.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.445-450
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• 1997

Optimal design of a piezoelectric smart structure is studied for cabin noise control. A cubic shaped acoustic cavity with a flat plate which covers one side is taken as the problem. The sensor signal is returned to the actuator through a negative gain. The acoustic cavity is modeled using the modal approach which represents the pressure fields in the cavity as a sum of mode shapes of the cavity with unknown coefficients. By using orthogonality of the mode shapes of the cavity, finite element equation for the structure with the influence of the acoustic cavity is derived. The objective function is the average pressure at a certain region, so-called silent zone, in the cavity and the design variables are the locations and sizes of the piezoelectric actuator and sensor. The optimal design is performed at several frequencies and the results show a remarkable noise reduction.