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  • Open Access

    ARTICLE

    Three Dimensional Acoustic Shape Sensitivity Analysis by Means of Adjoint Variable Method and Fast Multipole Boundary Element Approach

    C.J. Zheng1, H.B. Chen1, T. Matsumoto2, T. Takahashi2

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.1, pp. 1-30, 2011, DOI:10.3970/cmes.2011.079.001

    Abstract A fast multipole boundary element approach to the shape sensitivity analysis of three dimensional acoustic wave problems is developed in this study based on the adjoint variable method. The concept of material derivative is employed in the derivation. The Burton-Miller formula which is a linear combination of the conventional and normal derivative boundary integral equations is adopted to cope with the non-uniqueness problem when solving exterior acoustic wave problems. Constant elements are used to discretize the boundary surface so that the strongly- and hyper-singular boundary integrals contained in the formulations can be evaluated explicitly and More >

  • Open Access

    ARTICLE

    A Constitutive Model for Porous Shape Memory Alloys Considering the Effect of Hydrostatic Stress

    Bingfei Liu1, Guansuo Dui1,2, Yuping Zhu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 247-276, 2011, DOI:10.3970/cmes.2011.078.247

    Abstract A constitutive model considering the effect hydrostatic stresses induced by porosity on the macroscopic behavior of porous Shape Memory Alloys (SMAs) is developed in this paper. First, a unit-cell model is adopted to establish the constitutive relations for the porous SMAs with SMA matrix and the porosity taken to be voids. Dilatational plasticity theory is then generalized for the SMA matrix. Based on an approximation of the velocity field and the upper bound theory, an explicit yield function for the porous SMA is derived from micromechanical considerations. Finally, an example for the uniaxial response under More >

  • Open Access

    ARTICLE

    Topological Optimization of Anisotropic Heat Conducting Devices using Bezier-Smoothed Boundary Representation

    C.T.M. Anflor1, R.J. Marczak2

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 151-168, 2011, DOI:10.3970/cmes.2011.078.151

    Abstract This paper aims to demonstrate the final result of an optimization process when a smooth technique is introduced between intermediary iterations of a topological optimization. In a topological optimization process is usual irregular boundary results as the final shape. This boundary irregularity occurs when the way of the material is removed is not very suitable. Avoiding an optimization post-processing procedure some techniques of smooth are implemented in the original optimization code. In order to attain a regular boundary a smoothness technique is employed, which is, Bezier curves. An algorithm was also developed to detect during More >

  • Open Access

    ARTICLE

    Acoustic Design Shape and Topology Sensitivity Formulations Based on Adjoint Method and BEM

    T. Matsumoto1, T. Yamada1, T. Takahashi1, C.J. Zheng2, S. Harada1

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 77-94, 2011, DOI:10.3970/cmes.2011.078.077

    Abstract Shape design and topology sensitivity formulations for acoustic problems based on adjoint method and the boundary element method are presented and are applied to shape sensitivity analysis and topology optimization of acoustic field. The objective function is assumed to consist only of boundary integrals and quantities defined at certain number of discrete points. The adjoint field is defined so that the sensitivity of the objective function does not include the unknown sensitivity coefficients of the sound pressures and particle velocities on the boundary and in the domain. Since the final sensitivity expression does not have More >

  • Open Access

    ARTICLE

    Natural Convection in an Inclined T-Shaped Cavity

    Hicham Rouijaa1, Mustapha El Alami2, El Alami Semma3, Mostafa Najam2

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.1, pp. 57-70, 2011, DOI:10.3970/fdmp.2011.007.057

    Abstract This article presents a numerical study on natural convection in a bidimensional inclined "T"-shaped cavity. The governing equations are solved in the framework of a control-volume method resorting to the SIMPLEC algorithm (for the treatment of pressure-velocity coupling). Special emphasis is given to the investigation of the effect of inclination on the heat transfer and mass flow rate. Results are discussed for Prandtl number Pr=0.72, geometry with: opening width C=0.15, blocks gap D=0.5, blocks height, B=0.5 and different values of the Rayleigh number (104 ≤ Ra ≤ 106). More >

  • Open Access

    ARTICLE

    Fatigue Damage Accumulation in a Cu-based Shape Memory Alloy: Preliminary Investigation

    F. Casciati1, S. Casciati2, L. Faravelli1, A. Marzi1

    CMC-Computers, Materials & Continua, Vol.23, No.3, pp. 287-306, 2011, DOI:10.3970/cmc.2011.023.287

    Abstract The potential offered by the main features of shape memory alloys (SMA) in Structural Engineering applications is object of attention since two decades. The main issues concern the predictability of the material behavior and the fatigue lifetime of macro structural elements (as different from wire segments). In this paper, the fatigue characteristics, at given temperatures, of multigrain samples of a specific Cu-based alloy are investigated. The results of laboratory tests on bar specimens are discussed. The target is to model the manner in which the effects of several loading-unloading cycles of different amplitude cumulate. More >

  • Open Access

    ARTICLE

    TURBINE BLADE FILM COOLING USING PSP TECHNIQUE

    Je-Chin Han*, Akhilesh P. Rallabandi

    Frontiers in Heat and Mass Transfer, Vol.1, No.1, pp. 1-21, 2010, DOI:10.5098/hmt.v1.1.3001

    Abstract Film cooling is widely used to protect modern gas turbine blades and vanes from the ever increasing inlet temperatures. Film cooling involves a very complex turbulent flow-field, the characterization of which is necessary for reliable and economical design. Several experimental studies have focused on gas turbine blade, vane and end-wall film cooling over the past few decades. Measurements of heat transfer coefficients, film cooling effectiveness values and heat flux ratios using several different experimental methods have been reported. The emphasis of this current review is on the Pressure Sensitive Paint (PSP) mass transfer analogy to More >

  • Open Access

    ABSTRACT

    Anisotropic elastic properties of Ni-Mn-In magnetic shape memory alloy

    K. Williams1, T. Cagin1,2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.15, No.4, pp. 153-160, 2010, DOI:10.3970/icces.2010.015.153

    Abstract Designing magnetic shape memory materials with practicable engineering applications requires a thorough understanding of their electronic, magnetic, and mechanical properties. Experimental and computational studies on such materials provide differing perspectives on the same problems, with theoretical approaches offering fundamental insight into complex experimental phenomena. Many recent computational approaches have focused on first-principles calculations, all of which have been successful in reproducing ground-state structures and properties such as lattice parameters, magnetic moments, electronic density of states, and phonon dispersion curves. With all of these successes, however, such methods fail to include the effects of finite temperatures,… More >

  • Open Access

    ARTICLE

    Dynamic Modeling and Analysis of Arch Bridges Using Beam-Arch Segment Assembly

    Wei-Xin Ren1,2,3, Cong-Cong Su1, Wang-Ji Yan1

    CMES-Computer Modeling in Engineering & Sciences, Vol.70, No.1, pp. 67-92, 2010, DOI:10.3970/cmes.2010.070.067

    Abstract A beam-arch segment assembly procedure is presented in this paper for the dynamic modelling and analysis of arch bridges. Such a beam-arch segment assembly is composed of different structural elements of arch bridges such as arch ribs (curved beams), suspenders, girders and floor beams. Based on the energy principle in structural dynamics, the stiffness matrix and mass matrix of such an assembly are formulated. The proposed procedure is then implemented to carry out the free vibration analysis of the Jian concrete filled tubular arch bridge. It is demonstrated that the proposed beam-arch segment assembly procedure More >

  • Open Access

    ARTICLE

    Aerodynamic Shape Optimization of Airfoils in Unsteady Flow

    Anant Diwakar1, D. N.Srinath1, Sanjay Mittal1

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 61-90, 2010, DOI:10.3970/cmes.2010.069.061

    Abstract Aerodynamic shape optimization of airfoils is carried out for two values of Reynolds numbers: 103 and 104, for an angle of attack of 5o. The objective functions used are (a) maximization of lift (b) minimization of drag and (c) minimization of drag to lift ratio. The surface of the airfoil is parametrized by a 4th order non-uniform rational B-Spline (NURBS) curve with 61 control points. Unlike the efforts in the past, the relatively large number of control points used in this study offer a rich design shape with the possibility of local bumps and valleys on the… More >

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