• 동력기계공학회지
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• 제12권2호
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• pp.35-40
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• 2008

This paper deals with the free vibrations of conical shells with linearly variable thickness by the transfer influence coefficient method. The classical thin shell theory based upon the Flugge theory is assumed and the governing equations of a conical shell are written as a coupled set of first order matrix differential equations using the transfer matrix. The Runge-Kutta-Gill integration method is used to solve the governing differential equation. The natural frequencies and corresponding mode shapes are calculated numerically for the conical shells with linearly variable thickness and various boundary conditions at the edges. The present method is applied to conical shells with linearly varying thickness, and the effects of the semi-vertex angle, the number of circumferential waves and thickness ratio on vibration are studied.

• 대한기계학회논문집A
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• 제26권5호
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• pp.843-850
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• 2002

This paper presents a simulation method using the transmission line modeling to reduce simulation runtime of hydraulic control systems. This method is based on separating the system components each other using the transmission line elements prior to simulation, which leads to divide the simulated system into several subsystems suitable for an even more efficient integration. It can also handle nonlinearities and discontinuities without flag signal when restarting integration. By applying variable integration timestep to parallel hydraulic circuits via parallel processing, it is shown that simulation run-time can be reduced significantly compared with that of Runge Kutta method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.308-314
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• 2000

This study explores the free, out-of-plane vibrations of horizontally circular curved beams. The differential equations governing the free vibration of such beams, including the effects of warping and rotatory inertia, are derived and solved numerically. The Runge-Kutta method and the Determinant Search method combined with Regula-Falsi method are used to integrate the differential equations and to obtain the natural frequencies, respectively. The lowest three natural frequencies are calculated over a wide range of non-dimensional system parameters: the horizontal rise to span length ratio, the slenderness ratio, the stiffness parameter, and the warping parameter. It is expected that the results obtained herein can be used practically for the design of curved member systems.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.1-8
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• 2004

For the linearized differential algebraic equation of the nonlinear constrained system, exact initial values of the acceleration are needed to solve itself. It may be very troublesome to perform the inverse operation for obtaining the incremental quantities since the mass matrix contains the zero element in the diagonal. This fact makes the mass matrix impossible to be positive definite. To overcome this singularity phenomenon the mass matrix needs to be modified to allow the feasible application of predictor and corrector in the iterative computation. In this paper the proposed numerical algorithm based on the modified mass matrix combines the conventional implicit algorithm, Newton-Raphson method and Newmark method. The numerical example presents reliabilities for the proposed algorithm via comparisons of the 4th order Runge-kutta method. The proposed algorithm seems to be satisfactory even though the acceleration, Lagrange multiplier, and energy show unstable behaviour. Correspondingly, it provides one important clue to another algorithm for the enhancement of the numerical results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.142-144
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• 1996

For the accurate analysis of motional characteristics of electrical machines, it is needed to solve the motion equations together with the electromagnetic field equations. In this paper the sequential coupling of systems, the spring mass system and the electromagnetic system, is adopted. The induced current and the magnetic fields are calculated by FEM with given speed. And then, with the computed electromagnetic force, the mechanical equations are solved by the Runge-Kutta method. The above to processes are repeated sequentially to obtain the time domain solutions. The resultant values are applied to the energy conservation law to prove the usefulness of the proposed sequential method.

• BMB Reports
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• 제30권1호
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• pp.7-12
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• 1997

The kinetics of the interesterification of triolein and stearic acid catalyzed by immobilized Rhizopus delemar lipase were studied in a batch operation. In order to clarify the mechanisms of this reaction, three models are discussed under various conditions in terms of the ratio of triolein and stearic acid. The rate constants involved in the proposed model were determined by combining the numerical Gauss-elemination method, and the trial-and-error method so as to fit the calculated results with the experimental data. The accuracy of the obtained rate constants was confirmed after they were substituted for simultaneous differential equations and the equations simulated using an adaptive step-size Runge-Kutta method. Finally, the model which agrees with the calculated results and the experimental data was selected.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.169-177
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• 2005

A high resolution scheme for solving gas-liquid two-phase flows with cavitation is described. This scheme uses the curvilinear coordinate grid and solves the density based momentum equations for mixture of gas-liquid medium with a preconditioning method to treat both compressible and incompressible flow characteristics. The present preconditioned method is based on the Runge-Kutta explicit finite-difference scheme, and is improved by using the diagonalization, the flux difference splitting and the MUSCL-TVD schemes to save computational effort and to increase stability and resolvability, especially at gas-liquid contact surfaces. A homogeneous equilibrium cavitation model is used to treat the gas-liquid two-phase medium in cavitating flow as a locally homogeneous pseudo-single-phase medium. Therefore, it is easy to solve cavitating flow, including wave propagation, large density changes and incompressible flow characteristic at low Mach number. Some numerical results obtained by the present scheme are shown.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.167-175
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• 1997

The locus of a camshaft supported on camshaft bearings has been investigated using transient method. Forces applied to camshaft are composed of two components, one is transfer force between cam and tappet, the other is frictional force. These forces have been calculated using lumped mass model and EHL theory. ADI method has been used for numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As the result of analysis, it is found that camshaft bearings exist in the hydrodynamic lubrication condition.

• Tribology and Lubricants
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• 제13권4호
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• pp.53-59
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• 1997

The camshaft locus at camshaft beating in a direct acting OHC valve train system has been investigated using the transient method. Forces applied to the camsfiaft are composed of two components, one is the transfer force between the cam and the tappet, the other is the frictional force. These forces have been calculated using the lumped mass model and the elastohydrodynamic lubrication theory. The alternating direction implicit method has been used for the numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for the transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As a result of the analysis, it has been found that camshaft bearings were mainly in the hydrodynamic lubrication condition.

• 대한기계학회논문집
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• 제17권2호
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• pp.445-451
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• 1993

For the calculation of transonic laminar flow fields in cascades of turbomachinery, a finite volume method employing Jameson's Runge-Kutta integration scheme as a basic algorithm is presented. The cell-vertex scheme introducing half-spacing mesh cells is developed. For the velocity gradients in the stress terms the integration with divergence theorem is used for the average concept. Some numerical results show good agreement with experimental data.