• Title/Summary/Keyword: Euler equation

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Electrooptic Response of Reflective Liquid Crystal Cell

  • Lee, Geon-Joon;C. H. Oh;Lee, Y. P.;T. K. Lim
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.33-35
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    • 2003
  • The electrooptic properties of the reflected light in a reflective mode, $45^{\circ}C$twisted nematic liquid crystal (TNLC) cell were investigated in the voltage regions near and away from the Freedericksz transition threshold. The measured reflectivity away from the threshold voltage ($V_th$) could not be described by the model which assurnes a constant tilt angle as well as a linearized distribution of twist angle across the cell, although the data are well fitted near $V_th$. We found that in the voltage region away from $V_th$, the model considering the distributions of the tilt angle and the twist angle should be applied for the calculation of the reflectivity. The director-axis distributions were obtained from the numerical integration of the Euler-Lagrange equation.

SELF-SIMILAR SOLUTIONS FOR THE 2-D BURGERS SYSTEM IN INFINITE SUBSONIC CHANNELS

  • Song, Kyung-Woo
    • Bulletin of the Korean Mathematical Society
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    • v.47 no.1
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    • pp.29-37
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    • 2010
  • We establish the existence of weak solutions in an infinite subsonic channel in the self-similar plane to the two-dimensional Burgers system. We consider a boundary value problem in a fixed domain such that a part of the domain is degenerate, and the system becomes a second order elliptic equation in the channel. The problem is motivated by the study of the weak shock reflection problem and 2-D Riemann problems. The two-dimensional Burgers system is obtained through an asymptotic reduction of the 2-D full Euler equations to study weak shock reflection by a ramp.

Calculation of Turbulent Flows Using an Implicit Scheme on Two-Dimensional Unstructured Meshes (2차원 비정렬 격자에서의 내재적 기법을 이용한 난류 유동 계산)

  • Kang Hee Jung;Kwon Oh Joon
    • 한국전산유체공학회:학술대회논문집
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    • 1997.10a
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    • pp.29-37
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    • 1997
  • An implicit viscous turbulent flow solver is developed for two-dimensional geometries on unstructured triangular meshes. The flux terms are discretized based on a cell-centered finite-volume formulation with the Roe's flux-difference splitting. The solution is advanced in time using an implicit backward-Euler time-stepping scheme. At each time step, the linear system of equations is approximately solved with the Gauss-Seidel relaxation scheme. The effect of turbulence effects is approximated with a standard $k-{\varepsilon}$ two-equation model which is solved separately from the mean flow equations using the same backward-Euler time integration scheme. The triangular meshes are generated using an advancing-front/layer technique. Validations are made for flows over the NACA0012 airfoil and the Douglas 3-element airfoil. Good agreements are obtained between the numerical results and the experiment.

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A Dynamic Characteristics of the Tube Flow with the Variations of the Axially-Positioned Super-Circled Orifice Shape (유동방향의 초원형 오리피스 형상 변화가 관유동에 미치는 동특성 연구)

  • Kim, Youn J.;Lee, Sang-Sub
    • Journal of Energy Engineering
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    • v.6 no.1
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    • pp.52-57
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    • 1997
  • Dynamic characteristics of compressible flow fields in super-circled constricted tube have been studied numerically. By applying MacCormack's explicit scheme, time marching method with predictor/corrector step, Euler equation is solved to find characteristics of fluid flow in a constricted tube where a two-dimensional inviscid compressible flow is assumed. The effects of tube diameter and aspect ratios on the pressure variations are discussed extensively. The results of the developed numerical schemes are compared with those of commercial FLUENT code, and show a good agreement.

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Numerical Tests of Large Mass Method for Stress Calculation of Euler-Bernoulli Beams Subjected to Support Accelerations (지지점 가속도에 의해 가진되는 보의 응력계산에 대한 거대질량법의 정확도)

  • Kim, Yong-Woo;Choi, Nam Seok;Jhung, Myung Jo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.188-193
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    • 2013
  • The large mass method for dynamic analysis of statically determinate beams subjected to in-phase support motions is justified by showing that the equation of motion of the beams under consideration is equivalent to that of large mass model of the beam when an appropriate large mass ratio is employed. The accuracy of the stress responses based on the beam large mass method is investigated through careful numerical tests. The numerical results are compared to analytic solutions and the comparison shows that the large mass method yields not only the time history of motion but also the distributions of bending moment and shear force accurately.

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Non-Linear Behavior of Tapered Beams with Clamped-Roller Ends, subjected to a Concentrated Load (집중하중을 받는 변단면 고정-이동지점 보의 비선형 거동)

  • 이병구;이종국;최규문;김무영
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.10a
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    • pp.201-208
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    • 2000
  • This paper explores the non-linear behavior of tapered beam subjected to a floating concentrated load. For applying the Bernoulli-Euler beam theory to this beam, the bending moment at any point of elastica is obtained from the final equilibrium state. By using the bending moment equation and the Bernoulli-Euler beam theory, the differential equations governing the elastica of clamped-roller beam are derived, and solved numerically. Three kinds of tapered beam types are considered. The numerical results of the non-linear behavior obtained in this study are agreed quite well to the results obtained from the laboratory-scale experiments.

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The Effect of Series Center on the Convergence of the Solution in Vibration Analysis by Differential Transformation Method(DTM) (미분변환법에 의한 진동 해석시 급수중심이 해의 수렴에 미치는 영향)

  • Shin, Young-Jae;Yun, Jong-Hak;Yoo, Yeong-Chan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.2 s.257
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    • pp.231-236
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    • 2007
  • This paper presents the effect of the center of the series on convergence in solving vibration problems by Differential Transformation Method(DTM) to the transverse vibration of the Euler-Bernoulli beam under varying axial force. The governing differential equation of the transverse vibration of the Euler-Bernoulli beam under varying axial force is derived. The concepts of DTM were briefly introduced. Numerical calculations are carried out and compared with previously published results. The effect of the center of the series on convergence in solving the problem by DTM is discussed.

On forced and free vibrations of cutout squared beams

  • Almitani, Khalid H.;Abdelrahman, Alaa A.;Eltaher, Mohamed A.
    • Steel and Composite Structures
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    • v.32 no.5
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    • pp.643-655
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    • 2019
  • Perforation and cutouts of structures are compulsory in some modern applications such as in heat exchangers, nuclear power plants, filtration and microeletromicanical system (MEMS). This perforation complicates dynamic analyses of these structures. Thus, this work tends to introduce semi-analytical model capable of investigating the dynamic performance of perforated beam structure under free and forced conditions, for the first time. Closed forms for the equivalent geometrical and material characteristics of the regular square perforated beam regular square, are presented. The governing dynamical equation of motion is derived based on Euler-Bernoulli kinematic displacement. Closed forms for resonant frequencies, corresponding Eigen-mode functions and forced vibration time responses are derived. The proposed analytical procedure is proved and compared with both analytical and numerical analyses and good agreement is noticed. Parametric studies are conducted to illustrate effects of filling ratio and the number of holes on the free vibration characteristic, and forced vibration response of perforated beams. The obtained results are supportive in mechanical design of large devices and small systems (MEMS) based on perforated structure.

UNIFORMLY CONVERGENT NUMERICAL SCHEME FOR A SINGULARLY PERTURBED DIFFERENTIAL-DIFFERENCE EQUATIONS ARISING IN COMPUTATIONAL NEUROSCIENCE

  • DABA, IMIRU TAKELE;DURESSA, GEMECHIS FILE
    • Journal of applied mathematics & informatics
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    • v.39 no.5_6
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    • pp.655-676
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    • 2021
  • A parameter uniform numerical scheme is proposed for solving singularly perturbed parabolic partial differential-difference convection-diffusion equations with a small delay and advance parameters in reaction terms and spatial variable. Taylor's series expansion is applied to approximate problems with the delay and advance terms. The resulting singularly perturbed parabolic convection-diffusion equation is solved by utilizing the implicit Euler method for the temporal discretization and finite difference method for the spatial discretization on a uniform mesh. The proposed numerical scheme is shown to be an ε-uniformly convergent accurate of the first order in time and second-order in space directions. The efficiency of the scheme is proved by some numerical experiments and by comparing the results with other results. It has been found that the proposed numerical scheme gives a more accurate approximate solution than some available numerical methods in the literature.

CONSEQUENCE OF BACKWARD EULER AND CRANK-NICOLSOM TECHNIQUES IN THE FINITE ELEMENT MODEL FOR THE NUMERICAL SOLUTION OF VARIABLY SATURATED FLOW PROBLEMS

  • ISLAM, M.S.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.19 no.2
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    • pp.197-215
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    • 2015
  • Modeling water flow in variably saturated, porous media is important in many branches of science and engineering. Highly nonlinear relationships between water content and hydraulic conductivity and soil-water pressure result in very steep wetting fronts causing numerical problems. These include poor efficiency when modeling water infiltration into very dry porous media, and numerical oscillation near a steep wetting front. A one-dimensional finite element formulation is developed for the numerical simulation of variably saturated flow systems. First order backward Euler implicit and second order Crank-Nicolson time discretization schemes are adopted as a solution strategy in this formulation based on Picard and Newton iterative techniques. Five examples are used to investigate the numerical performance of two approaches and the different factors are highlighted that can affect their convergence and efficiency. The first test case deals with sharp moisture front that infiltrates into the soil column. It shows the capability of providing a mass-conservative behavior. Saturated conditions are not developed in the second test case. Involving of dry initial condition and steep wetting front are the main numerical complexity of the third test example. Fourth test case is a rapid infiltration of water from the surface, followed by a period of redistribution of the water due to the dynamic boundary condition. The last one-dimensional test case involves flow into a layered soil with variable initial conditions. The numerical results indicate that the Crank-Nicolson scheme is inefficient compared to fully implicit backward Euler scheme for the layered soil problem but offers same accuracy for the other homogeneous soil cases.