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  • Open Access

    ARTICLE

    Low Reynolds Numbers LDA-Experimental Analysis of the Near-Field of an Isothermal Laminar Round Free Jet

    A. Abbassi1,2, N. Kechiche1, H. Ben Aissia1

    FDMP-Fluid Dynamics & Materials Processing, Vol.10, No.3, pp. 319-341, 2014, DOI:10.3970/fdmp.2014.010.319

    Abstract Jet transition towards a turbulent state is an interesting topic requiring a detailed analysis of the process leading to the onset and amplification of small flow disturbances. Here we examine experimentally the transition process for an isothermal laminar round free jet at low values of the Reynolds number. Close to the inlet nozzle, the turbulence intensity is assumed to be small enough so that the initial shear layer can be considered laminar and the velocity profile uniform. Experimental data are obtained using a Laser Doppler Anemometry (LDA) technique at various longitudinal and transversal coordinates, (x,y). More >

  • Open Access

    ARTICLE

    A Discrete Fourier Transform Framework for Localization Relations

    D.T. Fullwood1, S.R. Kalidindi2, B.L. Adams1, S. Ahmadi1

    CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 25-40, 2009, DOI:10.3970/cmc.2009.009.025

    Abstract Localization relations arise naturally in the formulation of multi-scale models. They facilitate statistical analysis of local phenomena that may contribute to failure related properties. The computational burden of dealing with such relations is high and recent work has focused on spectral methods to provide more efficient models. Issues with the inherent integrations in the framework have led to a tendency towards calibration-based approaches. In this paper a discrete Fourier transform framework is introduced, leading to an extremely efficient basis for the localization relations. Previous issues with the Green's function integrals are resolved, and the method More >

  • Open Access

    ARTICLE

    Green's Function for Multilayers with Interfacial Membrane and Flexural Rigidities1

    B. Yang2, V. K. Tewary3

    CMC-Computers, Materials & Continua, Vol.8, No.1, pp. 23-32, 2008, DOI:10.3970/cmc.2008.008.023

    Abstract A three-dimensional Green's function for a material system consisting of anisotropic and linearly elastic planar multilayers with interfacial membrane and flexural rigidities has been derived. The Stroh formalism and two-dimensional Fourier transforms are applied to derive the general solution for each homogeneous layer. The Green's function for the multilayers is then solved by imposing the surface boundary condition, the interfacial displacement continuity condition, and the interfacial traction discontinuity condition. The last condition is given by the membrane and bending equilibrium equations of the interphases modeled as Kirchhoff plates. Numerical results that demonstrate the validity and More >

  • Open Access

    ARTICLE

    Fault Diagnosis of Motor in Frequency Domain Signal by Stacked De-noising Auto-encoder

    Xiaoping Zhao1, Jiaxin Wu1,*, Yonghong Zhang2, Yunqing Shi3, Lihua Wang2

    CMC-Computers, Materials & Continua, Vol.57, No.2, pp. 223-242, 2018, DOI:10.32604/cmc.2018.02490

    Abstract With the rapid development of mechanical equipment, mechanical health monitoring field has entered the era of big data. Deep learning has made a great achievement in the processing of large data of image and speech due to the powerful modeling capabilities, this also brings influence to the mechanical fault diagnosis field. Therefore, according to the characteristics of motor vibration signals (nonstationary and difficult to deal with) and mechanical ‘big data’, combined with deep learning, a motor fault diagnosis method based on stacked de-noising auto-encoder is proposed. The frequency domain signals obtained by the Fourier transform More >

  • Open Access

    ARTICLE

    Identification of Damaged Teeth in Gears using Wavelet Transform Applied to the Angular Vibration Signal

    P.A. Meroño1, F.C. Gómez2, F. Marín1

    CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 107-125, 2015, DOI:10.3970/cmc.2015.047.107

    Abstract This work represents a comparative study of Wavelet Transform of angular vibration signal and the traditional Fourier analysis applied to the signals of angular vibration, in one transmission which involve gears. How it is known, the elastic deformation of the material, together with the superficial irregularities of the teeth due to wear, provoke characteristic angular oscillations, which make it possible to distinguish between the regular functioning of a mechanism in good condition and the angular vibrations provoked by wear and the superficial irregularities of teeth in poor condition. However, the character of the vibrations produced More >

  • Open Access

    ARTICLE

    Heat Conduction Analysis of Nonhomogeneous Functionally Graded Three-Layer Media

    Chien-Ching Ma1,2, Yi-Tzu Chen2

    CMC-Computers, Materials & Continua, Vol.36, No.2, pp. 177-201, 2013, DOI:10.3970/cmc.2013.036.177

    Abstract Functionally graded material (FGM) is a particulate composite with continuously changing its thermal and mechanical properties in order to raise the bonding strength in the discrete composite made from different phases of material constituents. Furthermore, FGM is a potent tool to create an intermediate layer in metal–ceramic composites to avoid the properties discontinuities and reduce, thereby, the residual stresses. For the nonhomogeneous problem, the mathematical derivation is much complicated than the homogeneous case since the material properties vary with coordinate. To analyze the problem, the Fourier transform is applied and the general solution in transform… More >

  • Open Access

    ARTICLE

    Analytical Full-field Solutions of a Piezoelectric Layered Half-plane Subjected to Generalized Loadings

    Chien-Ching Ma1,2, Wen-Cha Wu2

    CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 79-108, 2009, DOI:10.3970/cmc.2009.011.079

    Abstract The two-dimensional problem of a planar transversely isotropic piezoelectric layered half-plane subjected to generalized line forces and edge dislocations in the layer is analyzed by using the Fourier-transform method and the series expansion technique. The full-field solutions for displacements, stresses, electrical displacements and electric fields are expressed in explicit closed forms. The complete solutions consist only of the simplest solutions for an infinite piezoelectric medium with applied loadings. It is shown in this study that the physical meaning of this solution is the image method. The explicit solutions include Green's function for originally applied loadings… More >

  • Open Access

    ARTICLE

    Benchmark Solutions for Three-Dimensional Transient Heat Transfer in Two-Dimensional Environments Via the Time Fourier Transform

    Julieta António1,2, António Tadeu2, Luís Godinho2, Nuno Simões2

    CMC-Computers, Materials & Continua, Vol.2, No.1, pp. 1-12, 2005, DOI:10.3970/cmc.2005.002.001

    Abstract The evaluation of heat propagation in the time domain generated by transient heat sources placed in the presence of three-dimensional media requires the use of computationally demanding numerical schemes. The implementation of numerical 3D solutions may benefit from the existence of benchmark solutions to test the accuracy of approximate schemes.
    With this purpose inmind, this article presents analyticalnumerical solutions to evaluate the heat-field elicited by monopole heat sources in the presence of three different inclusions, namely, a cylindrical circular solid inclusion, a cylindrical circular cavity with null fluxes and a cavity with null temperatures prescribed along… More >

  • Open Access

    ARTICLE

    A Matrix Decomposition MFS Algorithm for Biharmonic Problems in Annular Domains

    T. Tsangaris1, Y.–S. Smyrlis1, 2, A. Karageorghis1, 2

    CMC-Computers, Materials & Continua, Vol.1, No.3, pp. 245-258, 2004, DOI:10.3970/cmc.2004.001.245

    Abstract The Method of Fundamental Solutions (MFS) is a boundary-type method for the solution of certain elliptic boundary value problems. In this work, we develop an efficient matrix decomposition MFS algorithm for the solution of biharmonic problems in annular domains. The circulant structure of the matrices involved in the MFS discretization is exploited by using Fast Fourier Transforms. The algorithm is tested numerically on several examples. More >

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