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  • Open Access


    Mechanical Analyses of Casings in Boreholes, under Non-uniform Remote Crustal Stress Fields: Analytical & Numerical Methods

    Fei Yin1, Deli Gao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 25-38, 2012, DOI:10.3970/cmes.2012.089.025

    Abstract The methods to design the casings used in oilfields, are currently based on the assumptions that the remote crustal-stress-field is axially symmetric, in plane strain. However, most of the failures of the casings are caused by non-uniform and asymmetric far-field crustal stresses, so that it is necessary for a proper design of the casings, to investigate and understand the casing's behavior under non-uniform far-field crustal stresses. A mechanical model is first established for the system, consisting of the casing and formation, by using the plane strain theory of linear elasticity. The non-uniform crustal stress is… More >

  • Open Access


    On 3D FE Analyses For Understanding & Designing the Processes of Casing-Window-Milling for Sidetracking From Existing Wells

    Zhaohui Xu1, Deli Gao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 17-24, 2012, DOI:10.3970/cmes.2012.089.017

    Abstract Little is explained about the process of casing window milling for sidetracking due to lack of analytical method for its mechanical characteristic. In this paper, 3D FE models are established using the commercial finite-element software ABAQUS/Explicit to make simulation analysis for two key stages of the process including the initial stage of casing milling and the stage of full-gauge casing window milling. The models involve the effects of main drilling parameters such as reaction force, torque, speed, feed rate per revolution, and milling angle. The calculation results verify the capability and advantages of 3D FE More >

  • Open Access


    On a Method of Prediction of the Annular Pressure Buildup in Deepwater Wells for Oil & Gas

    Deli Gao1, Feng Qian1, Huikai Zheng1

    CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 1-16, 2012, DOI:10.3970/cmes.2012.089.001

    Abstract In deepwater wells for exploration and exploitation of oil & gas, the wellhead structure is of importance, and the annular pressure cannot be released after the casing hanger is set. The pressure changes in the casing annuli, caused by the temperature changes during the drilling and production processes, will increase the risk of failure of the casing. Therefore, a study of the safety of the casing in deepwater wells, by considering the complex engineering factors, will be of both academic as well as practical significance. In this paper, a model for the interactions among the… More >

  • Open Access


    MLPG6 for the Solution of Incompressible Flow Equations

    V. C. Loukopoulos1, G. C. Bourantas2

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 531-558, 2012, DOI:10.3970/cmes.2012.088.531

    Abstract Meshless Local Petrov-Galerkin (MLPG) approach is used for the solution of the Navier-Stokes and energy equations. More specific as a special case we apply the MLPG6 approach. In the MLPG6 method, the test function is chosen to be the same as the trial function (Galerkin method). The MLPG local weak form is written over a local sub-domain which is completely independent from the trial or test functions. The sizes of nodal trial and test function domains, as well as the size of the local sub-domain over which the local weak-form is considered, can be arbitrary.… More >

  • Open Access


    A New Anisotropic Local Meshing Method and Its Application in Parametric Surface Triangulation

    W.W. Zhang1, Y.F. Nie1, Y.Q. Li1

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 507-530, 2012, DOI:10.3970/cmes.2012.088.507

    Abstract A new algorithm for anisotropic triangular meshes generation in two dimension is presented. The inputs to the algorithm are the boundary geometry information and a metric tensor that specifies the desired element size and shape. The initial nodes are firstly distributed according to the above mentioned geometrical information, after bubble simulation, the optimized nodes set that meets the requirements of the metric tensor is obtained quickly. Then taking full advantage of the nodes set and the adjacency lists information provided by the process of node placement, a handful of non-satellite nodes are removed from the… More >

  • Open Access


    Asymmetric Shell Elements Based on a Corrected Updated-Lagrangian Approach

    P. Areias1,2,3, T. Rabczuk4, D. Dias-da-Costa5,6

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 475-506, 2012, DOI:10.3970/cmes.2012.088.475

    Abstract Surprisingly good displacement results are obtained by using the Petrov-Galerkin method with assumed and enhanced metric components in the test functions and enhanced metric components in the trial functions. Cartesian trial functions are required to ensure completeness and assumed/enhanced metric components are introduced to ensure high coarse-mesh accuracy. In the trial functions, the original incompatible-mode in-plane Q6 element by Wilson et al. can be used without violating the patch test. As a beneficial side-effect, Newton-Raphson convergence behavior for non-linear problems is improved. Transverse-shear and in-plane patch tests are satisfied while distorted-mesh performance is better than… More >

  • Open Access


    Analogy Between Rotating Euler-Bernoulli and Timoshenko Beams and Stiff Strings

    A.S Vinod Kumar, Ranjan Ganguli2

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 443-474, 2012, DOI:10.3970/cmes.2012.088.443

    Abstract The governing differential equation of a rotating beam becomes the stiff-string equation if we assume uniform tension. We find the tension in the stiff string which yields the same frequency as a rotating cantilever beam with a prescribed rotating speed and identical uniform mass and stiffness. This tension varies for different modes and are found by solving a transcendental equation using bisection method. We also find the location along the rotating beam where equivalent constant tension for the stiff string acts for a given mode. Both Euler-Bernoulli and Timoshenko beams are considered for numerical results. More >

  • Open Access


    The Second-Order Two-Scale Method for Heat Transfer Performances of Periodic Porous Materials with Interior Surface Radiation

    Zhiqiang Yang1, Junzhi Cui2, Yufeng Nie1, Qiang Ma2

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.5, pp. 419-442, 2012, DOI:10.3970/cmes.2012.088.419

    Abstract In this paper, a new second-order two-scale (SOTS) method is developed to predict heat transfer performances of periodic porous materials with interior surface radiation. Firstly, the second-order two-scale formulation for computing temperature field of the problem is given by means of construction way. Then, the error estimation of the second-order two-scale approximate solution is derived on some regularity hypothesis. Finally, the corresponding finite element algorithms are proposed and some numerical results are presented. They show that the SOTS method in this paper is feasible and valid for predicting the heat transfer performances of periodic porous More >

  • Open Access


    Hygrothermal Loading Effects in Bending Analysis of Multilayered Composite Plates

    S. Brischetto1

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.5, pp. 367-418, 2012, DOI:10.3970/cmes.2012.088.367

    Abstract The paper analyzes the hygrothermal loading effects in the bending of multilayered composite plates. Refined two-dimensional models are used to evaluate these effects, they are implemented in the framework of the Carrera's Unified Formulation (CUF) which also allows classical models to be obtained. Hygroscopic and thermal effects are evaluated by means of hygroscopic and thermal load applications, respectively. Such loads can be determined via a priori linear or constant moisture content and temperature profiles through the thickness of the plate, or by calculating them via the solution of the Fick moisture diffusion law and the More >

  • Open Access


    Computer Implementations with 3D Simulations of Models for Quick Estimations of Fragments Trajectories, Penetrations and Safety Evaluations Due to Detonations of Explosives

    Lior Banai

    CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.5, pp. 351-366, 2012, DOI:10.3970/cmes.2012.088.351

    Abstract The explosive Engineering field is a costly one in which not every organization can effort the time and money it takes to performed field tests on its explosives. The purpose of this article is to present a program that was developed in the Israeli Navy for performance estimations and safety issues of warheads and explosives. With a relative small developing time one can create a tool that gives preliminary results in a few minutes without the need to design and order a field tests or run finite elements analyses. By implementing a few known models, More >

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