• Selected Papers of The Society of Naval Architects of Korea
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• 제2권1호
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• pp.1-17
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• 1994

For a planar curve-sided panel with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach show that the surface integral can be transformed into contour integral by using Stokes'formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration (suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer time.

• 대한조선학회논문집
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• 제29권1호
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• pp.14-28
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• 1992

평면판 요소에 균일한 혹은 선형적인 세기를 갖는 쏘오스 또는 다이폴이 분포된 경우, Stokes 정리를 이용하여, 표면 특이점 분포방법에서 나타나는 표면 적분식을 선적분 형태로 변환할 수 있다. 더우기 판요소가 다각형인 경우, 유기 포텐시얼과 유기속도를 구하기 위한 이 선적분의 closed-forms을 유도하였다. 이들 적분식의 해석적 계산을 통해 계산시간을 단축하고 수치해의 정도를 향상시킬 수 있을 것이다. 몇개의 계산예를 통해 해석적 적분 계산이 수치적 적분보다 우수함을 알 수 있다.

• 대한조선학회지
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• 제16권4호
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• pp.13-21
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• 1979

A method of evaluating Kelvin wave pattern is presented in this paper. The mathematical manipulation of x-derivative of the Green function of the Havelock source by the use of contour integration on the complex plane has resulted in the expression that can be readily incorporated with computer program. The efficiency and accuracy that can be secured by the use of the present mathematical expressions seem to be excellent when suitable numerical quadratures are employed. The wave patterns for particular submergences of the singularity are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.104-106
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• 2005

In this paper, 3-dimensional magnetic field of coil is analyzed by using biot-sarvart law considering singularity. The RMSP(reduced magnetic scalar potential) arc employed in order to reduce the number of unknown variables in FEM(Finte Element Analysis) or BEM(Boundary Element Method). It Is necessary to calculate magnetic field of souce current when RMSP is used. Biot-savart law is generally used. it is difficult to calculate the field when the source point is in inside the coil. To integrate using gaussian quadrature, the cross section of coil is divided considering the position of field point when field point is inside coil. The proposed method shows good agreement of magnetic field compared with FEMLAB, OPERA3D.

• 대한조선학회지
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• 제18권4호
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• pp.1-11
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• 1981

A flow problem around a ship hull with the nonlinear free surface boundary condition has been considered within the potential flow assumption. The Green's function based on the hull boundary condition is constructed numerically and used to satisfy the free surface boundary condition. This singularity to be distributed ideally on the undulating free surface is put actually, for practical reasons, on the flat water surface with the assumption of linear variation of velocities between the two positions. The surfaces of singularity distribution are approximated by Hess and Smith type quadrilaterals. The radiation condition is only crudely satisfied and this produced one of the major difficulties arising in the present way of attacking the problem.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1597-1604
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• 2005

The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.197-200
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• 2000

In this paper, we present a novel methodology for a wideband HTS antenna of finite length placed on a dielectric substrate. A methodology used in this work is based on a moment-method techniques with Green function singularity when the field point is in the source triangle. The designed resonance frequency of our HTS antenna is 11.85 GHz. The return loss is -26 dB. The bandwidth obtained is a significant 10.6 %. Experimental measurements for a HTS antenna designed in X-band are shown to agree well with the simulated prediction.

• 한국소음진동공학회논문집
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• 제24권7호
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• pp.569-574
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• 2014

In order to investigate low frequency swishing noise of wind turbines, acoustic source model using a singularity in circular motion is introduced to derive analytic solution of Lowson acoustic analogy in time domain. Results in time and frequency domains computed by the solution show apparent modulation of amplitude and frequency. The solution indicates that time histories of acoustic pressure at receiver points varied significantly according to receiver's directional location, even when the retarded time distributions are similar. However, the corresponding time-averaged spectra of sound pressure at the receiver locations where the retarded time distributions are almost same are not significantly different. It can be inferred from these results that the time-averaged sound pressure spectra which cannot take into account the detailed difference in the time-variation of wind turbine noise may not represent the sound quality of wind turbines due to its swishing. Finally, as an introduction of procedure to quantify low frequency swishing noise level, relative variation of overall sound pressure level is obtained using tonal low frequency noise model.

• 대한수학회지
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• 제37권5호
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• pp.779-791
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• 2000

The nonlinear stage of the evolution of free boundary between a light fluid and a heavy fluid driven by an external force is studied by a potential flow model with a source singlarity. The potential flow model is applied to a bubble and spije evolution for constantly accelerated interface (Rayleigh-Taylor instability) and impulsively accelerated interface (Richtmyer-Meshkow instability). The numerical results of the model show that, in constantly accelerated intergace, bubble grows with constant velocity and the spike falls with gravitational acceleration at later times, while the velocity of the bubble in impulsively accelerated interface decay to zero asymp flow model for the bubble and spike for constantly accelerated interface and impulsively accelerated interface.

• Journal of Hydrospace Technology
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• 제2권2호
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• pp.36-43
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• 1996

In this work, a panel method is described, which cart solve the flow field round a surface-piercing body that experiences lift and wave resistance. As the body boundary condition, a Dirichlet type is employed, and as the free surface boundary condition the Poisson type is implemented, while in its discretization Dawson's 4-point upwind difference scheme is utilized, and as the Kutta condition a Morino-Kuo type is chosen. As to the type of singularity, source panels are distributed on the free surface, and source and dipole panels on the body surface, and dipole panels on the wake surface. For a sample run, a catamaran of the parabolic Wigley hull is chosen, for which experimental data are available, and the predictions by the numerical means and by the experiment are compared for a wide range of parameters.