D.N. Srinath¹, Sanjay Mittal¹, Veera Manek²

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.2, pp. 169-190, 2009, DOI:10.3970/cmes.2009.051.169

Abstract A continuous adjoint method is formulated and implemented for the multi-point shape optimization of airfoils at low Re. The airfoil shape is parametrized with a non-uniform rational B-Spline (NURBS). Optimization studies are carried out for two different objective functions. The first involves an inverse function on the lift coefficient over a range of Re. The objective is to determine a shape that results in a lift coefficient of 0.4 at three values of Re: 10, 100 and 500. The second objective involves a direct function on the lift coefficient over a range of angles of More >

S.Yu. Reutskiy¹

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.2, pp. 115-142, 2009, DOI:10.3970/cmes.2009.051.115

Abstract In this paper a new numerical technique for problems of free vibrations of arbitrary shaped non-homogeneous membranes:∇²w + k²q(x)w = 0, x∈ Ω⊂R², B[w] = 0, x∈∂Ω is presented. Homogeneous membranes of a complex form are considered as a particular case. The method is based on mathematically modeling of physical response of a system to excitation over a range of frequencies. The response amplitudes are then used to determine the resonant frequencies. Applying the method, one gets a sequence of boundary value problems (BVPs) depending on the spectral parameter k. The eigenvalues are sought as positions of More >

T. Starling¹, M. F. Daqaq¹, G. Li^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.45, No.3, pp. 207-226, 2009, DOI:10.3970/cmes.2009.045.207

Abstract Input-shaping is an open-loop control technique for dynamic control of electrostatic MEMS. In MEMS applications, open-loop control is attractive as it computes a priori the required system input to achieve desired dynamic behavior without using feedback. In this work, a 3-D computational electromechanical analysis is performed to preshape the voltage commands applied to electrostatically actuate a torsional micromirror to a desired tilt angle with minimal residual oscillations. The effect of higher vibration modes on the controlled response is also investigated. It is shown that, for some structural design parameters, the first bending mode of the More >

Cheng-Hung Huang¹, Yun-Lung Chung¹

CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.3, pp. 249-280, 2009, DOI:10.3970/cmes.2009.044.249

Abstract The optimum shapes for the longitudinal and spine fully wet fins are estimated in the present inverse design problem by using the conjugate gradient method (CGM) based on the desired fin efficiency and fin volume. One of the advantages in using CGM in the inverse design problem lies in that it can handle problems having a large number of unknown parameters easily and converges very fast. Results obtained by using the CGM to solve the inverse design problems are justified based on the numerical experiments. Results show that when the Biot number and relative humidity More >

Aimin Jiang^1,2, Yili Wu²

CMC-Computers, Materials & Continua, Vol.12, No.2, pp. 101-120, 2009, DOI:10.3970/cmc.2009.012.101

Abstract This paper presents a development of the boundary contour method (BCM) for piezoelectric media. Firstly, the divergence-free of the integrand of the piezoelectric boundary element method is proved. Secondly, the boundary contour method formulations are obtained by introducing quadratic shape functions and Green's functions (Computer Methods in Applied Mechanics and Engineering1998;158: 65-80) for piezoelectric media and using the rigid body motion solution to regularize the BCM and avoid computation of the corner tensor. The BCM is applied to the problem of piezoelectric media. Finally, numerical solutions for illustrative examples are compared with exact ones. The More >

CMC-Computers, Materials & Continua, Vol.10, No.1, pp. 65-96, 2009, DOI:10.3970/cmc.2009.010.065

Abstract This work proposed an alternative formulation for the prediction of martensite start temperature (Ms) of Fe-Mn-Si shape memory alloys (SMAs) depending on the various compositions and heat treatment techniques by using Neural Network (NN) and genetic programming (GP) soft computing techniques. The training and testing patterns of the proposed NN and GP formulations are based on well established experimental results from the literature. The NN and GP based formulation results are compared with experimental results and found to be quite reliable with a very high correlation (R2=0.955 for GEP and 0.999 for NN). More >

YANG Song-lin¹, MA Qing-wei², CHEN Shu-ling¹, GAO Lei¹, WU An¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.5, No.1, pp. 7-14, 2008, DOI:10.3970/icces.2008.005.007

Abstract An 11.8m-long gliding-hydrofoil craft with a T-formed hydrofoil and shallow V-shaped bottom is chosen to carry on in this work. Resistance test in towering tank is the main method. Two different installation angle (-1.5° and 0° ) of hydrofoil are conducted and the tests were done separately. Relevant results of different resistance performance have been got under the influence of different hydrofoil installation angle. More >

Z.D. Wang¹, D.F Li¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.5, No.4, pp. 245-254, 2008, DOI:10.3970/icces.2008.005.245

Abstract The thermo-mechanical constitution of shape memory polymers (SMPs) is critical for predicting their deformation and recovery characteristics under different constraints. In this study, a new, physical-based, temperature and time-dependent constitutive model is proposed for simulating the thermomechanical response of SMPs. The deformation mechanisms of shape fix and shape recovery are analyzed. Different models are compared to compare strain and stress recovery responses with the experimental results. More >

Hokyung Shim¹, Vinh Thuy Tran Ho^1,,Semyung Wang^1,2, Daniel A. Tortorelli³

CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.2, pp. 175-202, 2008, DOI:10.3970/cmes.2008.037.175

Abstract This paper presents a topological shape optimization technique for electromagnetic problems using a level set method and radial basis functions. The proposed technique is a level set (LS) based optimization dealing with geometrical shape derivatives and topological design. The shape derivative is computed by an adjoint variable method to avoid numerous sensitivity evaluations. A level set model embedded into the scalar function of higher dimensions is propagated to represent the design boundary of a domain. The level set function interpolated into a fixed initial domain is evolved by using the Hamilton-Jacobi equation. The moving free… More >

Cheng-Hung Huang¹, Chi-An Chen¹

CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.1, pp. 1-22, 2008, DOI:10.3970/cmes.2008.036.001

Abstract A three-dimensional shape identification problem (or inverse geometry problem) in estimating the unknown irregular shape of internal cavity by using the steepest descent method (SDM) and a general purpose commercial code CFD-RC is examined in this study based on the simulated measured temperature distributions on the outer surface by infrared thermography. The advantage of calling CFD-RC as a subroutine in the present shape identification problem lies in its characteristics of easily-handling the problem considered here since the auto mesh function of CFD-RC enables the handling of this moving boundary problem. \newline Three test cases are More >