• 제목/요약/키워드: Convection-diffusion

검색결과 226건 처리시간 0.021초

SCHWARZ METHOD FOR SINGULARLY PERTURBED SECOND ORDER CONVECTION-DIFFUSION EQUATIONS

  • ROJA, J. CHRISTY;TAMILSELVAN, A.
    • Journal of applied mathematics & informatics
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    • 제36권3_4호
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    • pp.181-203
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    • 2018
  • In this paper, we have constructed an overlapping Schwarz method for singularly perturbed second order convection-diffusion equations. The method splits the original domain into two overlapping subdomains. A hybrid difference scheme is proposed in which on the boundary layer region we use the central finite difference scheme on a uniform mesh while on the non-layer region we use the mid-point difference scheme on a uniform mesh. It is shown that the numerical approximations which converge in the maximum norm to the exact solution. When appropriate subdomains are used, the numerical approximations generated from the method are shown to be first order convergent. Furthermore it is shown that, two iterations are sufficient to achieve the expected accuracy. Numerical examples are presented to support the theoretical results. The main advantages of this method used with the proposed scheme is it reduces iteration counts very much and easily identifies in which iteration the Schwarz iterate terminates.

Uniformly Convergent Numerical Method for Singularly Perturbed Convection-Diffusion Problems

  • Turuna, Derartu Ayansa;Woldaregay, Mesfin Mekuria;Duressa, Gemechis File
    • Kyungpook Mathematical Journal
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    • 제60권3호
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    • pp.629-645
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    • 2020
  • A uniformly convergent numerical method is developed for solving singularly perturbed 1-D parabolic convection-diffusion problems. The developed method applies a non-standard finite difference method for the spatial derivative discretization and uses the implicit Runge-Kutta method for the semi-discrete scheme. The convergence of the method is analyzed, and it is shown to be first order convergent. To validate the applicability of the proposed method two model examples are considered and solved for different perturbation parameters and mesh sizes. The numerical and experimental results agree well with the theoretical findings.

NUMERICAL COMPARISON OF WENO TYPE SCHEMES TO THE SIMULATIONS OF THIN FILMS

  • Kang, Myungjoo;Kim, Chang Ho;Ha, Youngsoo
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제16권3호
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    • pp.193-204
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    • 2012
  • This paper is comparing numerical schemes for a differential equation with convection and fourth-order diffusion. Our model equation is $h_t+(h^2-h^3)_x=-(h^3h_{xxx})_x$, which arises in the context of thin film flow driven the competing effects of an induced surface tension gradient and gravity. These films arise in thin coating flows and are of great technical and scientific interest. Here we focus on the several numerical methods to apply the model equation and the comparison and analysis of the numerical results. The convection terms are treated with well known WENO methods and the diffusion term is treated implicitly. The diffusion and convection schemes are combined using a fractional step-splitting method.

A WEAKLY COUPLED SYSTEM OF SINGULARLY PERTURBED CONVECTION-DIFFUSION EQUATIONS WITH DISCONTINUOUS SOURCE TERM

  • BABU, A. RAMESH;VALANARASU, T.
    • Journal of applied mathematics & informatics
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    • 제37권5_6호
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    • pp.357-382
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    • 2019
  • In this paper, we consider boundary value problem for a weakly coupled system of two singularly perturbed differential equations of convection diffusion type with discontinuous source term. In general, solution of this type of problems exhibits interior and boundary layers. A numerical method based on streamline diffusiom finite element and Shishkin meshes is presented. We derive an error estimate of order $O(N^{-2}\;{\ln}^2\;N$) in the maximum norm with respect to the perturbation parameters. Numerical experiments are also presented to support our theoritical results.

FITTED OPERATOR ON THE CRANK-NICOLSON SCHEME FOR SOLVING A SMALL TIME DELAYED CONVECTION-DIFFUSION EQUATIONS

  • TEFERA, DAGNACHEW MENGSTIE;TIRUNEH, AWOKE ANDARGIE;DERESE, GETACHEW ADAMU
    • Journal of applied mathematics & informatics
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    • 제40권3_4호
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    • pp.491-505
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    • 2022
  • This paper is concerned with singularly perturbed convection-diffusion parabolic partial differential equations which have time-delayed. We used the Crank-Nicolson(CN) scheme to build a fitted operator to solve the problem. The underling method's stability is investigated, and it is found to be unconditionally stable. We have shown graphically the unstableness of CN-scheme without fitting factor. The order of convergence of the present method is shown to be second order both in space and time in relation to the perturbation parameter. The efficiency of the scheme is demonstrated using model examples and the proposed technique is more accurate than the standard CN-method and some methods available in the literature, according to the findings.

Generic studies on thermo-solutal convection of mercurous chloride system of ${Hg_2}{Cl_2}$ and Ne during physical vapor transport

  • Choi, Jeong-Gil;Lee, Kyong-Hwan;Kim, Geug-Tae
    • 한국결정성장학회지
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    • 제19권1호
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    • pp.39-47
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    • 2009
  • The effects of thermo-solutal convection on mercurous chloride system of ${Hg_2}{Cl_2}$, and Ne during physical vapor transport are numerically investigated for further understanding and insight into essence of transport phenomena, For $10\;K{\le}{\Delta}T{\le}30\;K$, the growth rate slowly increases and, then is decreased gradually until ${\Delta}T$=50 K, The occurrence of this critical point near at ${\Delta}T$=30 K is likely to be due to the effects of thermo-physical properties stronger than the temperature gradient corresponding to driving force for thermal convection. For the range of $10\;Torr{\le}P_B{\le}300\;Torr$, the rate is second order-exponentially decayed with partial pressures of component B, $P_B$. For the range of $5{\le}M_B{\le}200$, the rate is second order-exponentially decayed with a function of molecular weight of component B, $M_B$. Like the case of a partial pressure of component B, the effects of a molecular weight arc: reflected through the binary diffusivity coefficients, which are intimately related with suppressing the convection flow inside the growth enclosure, i,e., transition from convection to diffusion-dominant flow mode as the molecular weight of B increases. The convective mode is near at a ground level, i,e., on earth (1 $g_0$), and the convection is switched to the diffusion mode for $0.1\;g_0{\le}g{\le}10^{-2}g_0$, whereas the diffusion region ranges from $10^{-2}g_0$ up to $10^{-5}g_0$.

고차 정확도의 순수 상류 차분법의 개발 (Development of a High Accuracy Pure Upwind Difference Scheme)

  • 조지룡
    • 한국전산유체공학회지
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    • 제4권1호
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    • pp.8-18
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    • 1999
  • In devising a numerical approximation for the convective spatial transport of a fluid mechanical quantity, it is noted that the convective motion of a scalar quantity occurs in one-way, or from upstream to downstream. This consideration leads to a new scheme termed a pure upwind difference scheme (PUDS) in which an estimated value for a fluid mechanical quantity at a control surface is not influenced from downstream values. The formal accuracy of the proposed scheme is third order accurate. Two typical benchmark problems of a wall-driven fluid flow in a square cavity and a buoyancy-driven natural convection in a tall cavity are computed to evaluate performance of the proposed method. for comparison, the widely used simple upwind scheme, power-law scheme, and QUICK methods are also considered. Computation results are encouraging: the proposed PUDS sensitized to the convection direction produces the least numerical diffusion among tested convection schemes, and, notable improvements in representing recirculation of fluid stream and spatial change of a scalar. Although the formal accuracy of PUDS and QUICK are the same, the accuracy difference of approximately a single order is observed from the revealed results.

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A NUMERICAL METHOD FOR SINGULARLY PERTURBED SYSTEM OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS OF CONVECTION DIFFUSION TYPE WITH A DISCONTINUOUS SOURCE TERM

  • Tamilselvan, A.;Ramanujam, N.
    • Journal of applied mathematics & informatics
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    • 제27권5_6호
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    • pp.1279-1292
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    • 2009
  • In this paper, a numerical method that uses standard finite difference scheme defined on Shishkin mesh for a weakly coupled system of two singularly perturbed convection-diffusion second order ordinary differential equations with a discontinuous source term is presented. An error estimate is derived to show that the method is uniformly convergent with respect to the singular perturbation parameter. Numerical results are presented to illustrate the theoretical results.

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RECURSIVE TWO-LEVEL ILU PRECONDITIONER FOR NONSYMMETRIC M-MATRICES

  • Guessous, N.;Souhar, O.
    • Journal of applied mathematics & informatics
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    • 제16권1_2호
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    • pp.19-35
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    • 2004
  • We develop in this paper some preconditioners for sparse non-symmetric M-matrices, which combine a recursive two-level block I LU factorization with multigrid method, we compare these preconditioners on matrices arising from discretized convection-diffusion equations using up-wind finite difference schemes and multigrid orderings, some comparison theorems and experiment results are demonstrated.

APPROXIMATION OF DERIVATIVE TO A SINGULARLY PERTURBED REACTION-CONVECTION-DIFFUSION PROBLEM WITH TWO PARAMETERS.

  • Priyadharshini, R. Mythili;Ramanujam, N.
    • Journal of applied mathematics & informatics
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    • 제27권3_4호
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    • pp.517-529
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    • 2009
  • In this paper, a singularly perturbed reaction-convection-diffusion problem with two parameters is considered. A parameter-uniform error bound for the numerical derivative is derived. The numerical method considered here is a standard finite difference scheme on piecewise-uniform Shishkin mesh, which is fitted to both boundary and initial layers. Numerical results are provided to illustrate the theoretical results.

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