Cui Li¹, Deli Gao¹, Zhiyong Wu¹, Binbin Diao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 39-56, 2012, DOI:10.3970/cmes.2012.089.039

Abstract At present, a relief well is the most reliable method to control serious blowout accidents, and it is necessary to detect very accurately the relative position of the relief well and the blowout well. The detection tool should be capable of detecting directly the relative distance and direction between the relief well and the blowout well. Its detection accuracy should also meet the engineering demand of drilling a relief well. Using the working principle of a proposed detection tool, this paper analyzes the spread and attenuation laws of the current injected by a single-electrode or More >

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 >

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 >

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 >

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 >

P. Areias^1,2,3, T. Rabczuk⁴, D. Dias-da-Costa^5,6

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 >

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 >

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 >

Changsheng Wang¹, Ping Hu^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.5, pp. 325-350, 2012, DOI:10.3970/cmes.2012.088.325

Abstract Based on the Reissner-Mindlin plate theory, two 3-node triangular flat shell elements QCS31 and QCS32 are proposed by using Timoshenko's beam function within the framework of quasi-conforming technique. The exact displacement function of the Timoshenko's beam is used as the displacement on the element boundary in the bending part and the interpolated inner field function is also derived by the function. In the shear part the re-constitution technique is adopted. The drilling degrees of freedom are added in the membrane part to improve membrane behavior. The proposed elements can be used for the analysis of More >

Ridha Djebali^1,2, Bernard Pateyron², Mohamed El Ganaoui³

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.4, pp. 293-308, 2012, DOI:10.3970/cmes.2012.088.293

Abstract We present in this study a numerical investigation of unsteady two-dimensional natural convection of an electrically conducting fluid in a square cavity under an externally imposed magnetic field. A temperature gradient is applied between the two opposing side walls parallel to y-direction, while the floor and ceiling parallel to x-direction are adiabatic. The flow is characterized by the Rayleigh number Ra raged in 103-106, the Prandtl number Pr ranged in 0.01-10, the Hartman number Ha determined by the strength of the imposed magnetic field ranged in 0-100 and its tilting angle from x-axis ranging from… More >