• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.45-54
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• 한국소음진동공학회논문집
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• 제22권6호
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• pp.524-534
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제22권4호
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• pp.289-294
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• 2018

In this work, a recently developed semi-analytic technique, so called the residual power series method, is generalized to process higher-dimensional linear and nonlinear partial differential equations. The solutions obtained takes a form of an infinite power series which can, in turn, be expressed in a closed exact form. The results reveal that the proposed generalization is very effective, convenient and simple. This is achieved by handling the (m+1)-dimensional Burgers equation.

• 한국해안해양공학회지
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• 제19권3호
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• pp.183-193
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• 2007

부분반사 전면 및 완전반사 후면을 갖는 반무한 방파제 및 방파제 개구부에 의한 파의 산란 현상에 대한 해석 해를 유도하였다. 이는 수심이 일정하고 파가 방파제에 직각으로 입사하는 경우에 적용 가능하며, 선형파 이론에 근거하여 변수 변환 및 좌표 변환을 통해 지배 방정식을 상미분 방정식으로 전환하여 구하였다. 본 연구에서 유도된 해석 해는 유한 요소 수치 모델의 결과와 비교하여 그 정확도를 비교하였는데, 꽤 정확한 결과를 보인다는 것을 알 수 있었다. 유도된 해석 해를 이용하여 방파제에서의 반사율에 따른 항 입구에서의 정온도에 미치는 효과를 조사하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.491-496
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• 2003

In sensitivity analysis, semi-analytical method(SAM) reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Recently such errors of SAM resulted by the finite difference scheme have been improved by the separation of rigid body mode. But the eigenvalue should be obtained first before the sensitivity analysis is performed and it takes much time in the case that large system is considered. In the present study, by constructing a reduced one from the original system, iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The sensitivity analysis is performed by the eigenvector acquired from the reduced system. The error of SAM caused by difference scheme is alleviated by Von Neumann series approximation.

• 대한기계학회논문집
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• 제17권1호
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• pp.11-20
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• 1993

본 연구에서는 준 해석적 방법에 촛점을 맞추어 전개를 하려 한다. 대개의 최적설계방식이 그렇듯 준 해석적 방법도 치수변수에 관해 응용이 이루어졌는데 그 정 확도에 문제가 나타나지는 않는다. 그러나 최근 형상변수에 대해 응용을 할 경우 오 차가 큰 것이 발견되었다. 물론 치수변수에 관해서도 준 해석적 방법에서 오차가 존 재한다는 보고 있으나 그 절대량이 크지 않으므로 그다지 심각하지 않다고 사료된다. 여기서는 준해석적 방법의 오차의 과정이 수학적으로 전개될 것이며, 설정된 구조물에 대한 수치적 계산결과가 논의 될 것이다. 해석의 대상 구조물로는 엄밀해가 존재하 여 비교분석이 용이한 2차원 외팔보가 선택되었으며, 여러가지 방법과의 비교로서 준 해석적 방법이 논의되고 효과적인 방법선택이 제안될 것이다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제7권2호
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• pp.75-81
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• 2003

Compact schemes are shown to be effective for a class of problems including convection-diffusion equations when combined with multigrid algorithms [7, 8] and V-cycle convergence is proved[5]. We apply the multigrid algorithm for an semianalytic finite difference scheme, which is desinged to preserve high order accuracy despite of singularities.

• Geosystem Engineering
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• 제21권6호
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• pp.309-317
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• 2018

We employ a three-dimensional indirect boundary element method (BEM) to simulate temperature change around an underground liquefied natural gas storage cavern. The indirect BEM (IBEM) uses fictitious heat source strength on boundary elements as basic variables which are solved from equations of boundary conditions and then used to compute the temperature change at other points in the considered problem domain. The IBEM requires evaluation of singular integration for temperature change due to heat conduction from a constant heat source on a planar (triangular) region. The singularity can be eliminated by a semi-analytical integration scheme. However, it is found that the semi-analytical integration scheme yields sharp temperature gradient for points close to vertices of triangle. This affects the accuracy of heat flux, if they are evaluated by finite difference method at these points. This difficulty can be overcome by a combination of using a direct numerical integration for these points and the semi-analytical scheme for other points distance away from the vertices. The IBEM and the hybrid integration scheme have been verified with an analytic solution and then used to the application of the underground storage.

• 소성∙가공
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• 제8권4호
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• pp.374-383
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• 1999

To determine the flow stress of semi-solid materials, a new combined method has been studied by experimental and analytic technique in the current approach. Using backward extrusion experiment and its numerical analysis, the characterization scheme of semi-solid materials according to the change of initial solid volume fraction has been proposed. Because that solid volume fraction is sensitive to temperature change, it is required to precisely control the temperature setting. Model materials can guarantee the establishment of material characterization technique from the noise due to temperature change. Thus, clay mixed with bonded abrasives was used for experiment and the change of initial solid fraction was copied out through the variation of mixing ratio. Upper bound method was adapted to increase in efficiency of the calculation in numerical analysis and new kinematically admissible velocity field was employed to improve the accuracy of numerical solution. It is thought that the material characterization scheme proposed in this study can be applied to not only semi-solid materials, but also other materials that is difficult to obtain the simple stress state.

• 한국생산제조학회지
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• 제21권5호
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• pp.741-746
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• 2012

The increase of energetic efficiency in plane bearing is getting more important in the transfer mechanism of semi-conductor and display panel manufacturing processes. To accomplish this objective, the technique of surface texturing on bearing surface has recently emerged as one of the most effective candidates. In this study, the effects of various pattern parameters on two bearing performance indices(load carrying capacity and effective friction coefficient) are investigated through a semi-analytic method, i.e., the 2-dimensional Reynolds equation incorporated into the finite difference scheme. Here, cavitation effect is also taken into account by employing an appropriate numerical scheme. In this study, the patterns in the textured surface are composed of a series of semi-spheres or semi-ellipsoids in shape. The effects of their size and number density on the performance indices are examined through the performance of various numerical experiments. Also, the effects of the anisotropy of the semi-ellipsoidal pattern on the bearing's lubrication characteristics are investigated and discussed.