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Optimization of wall electrodes for electrohydrodynamic control of natural convection effects during solidification
 J. of Materials and Manufacturing Processes
, 2004
"... This paper presents a numerical procedure to reduce and possibly control the natural convection effects in a cavity filled with a molten material by applying an external electric field whose intensity and spatial distributions are obtained by the use of a hybrid optimizer. This conceptually new appr ..."
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This paper presents a numerical procedure to reduce and possibly control the natural convection effects in a cavity filled with a molten material by applying an external electric field whose intensity and spatial distributions are obtained by the use of a hybrid optimizer. This conceptually new approach to manufacturing could be used in creation of layered and functionally graded materials and objects. In the case of steady electrohydrodynamics (EHD), the flowfield of electrically charged particles in a solidifying melt is influenced by an externally applied electric field while the existence of any magnetic field is neglected. Solidification front shape, distribution of the charged particles in the accrued solid, and the amount of accrued solid phase in such processes can be influenced by an appropriate distribution and orientation of the electric field. The intensities of the electrodes along the boundaries of the cavity were described using Bsplines. The inverse problem was then formulated to find the electric boundary conditions (the coefficients of the Bsplines) in such a way that the gradients of temperature along the horizontal direction are minimized. 1
HYBRID OPTIMIZATION WITH AUTOMATIC SWITCHING AMONG OPTIMIZATION ALGORITHMS
"... Abstract. In this chapter we present a hybrid approach to optimization problems, where we use deterministic and stochastic/evolutionary optimization algorithms. The basic idea is to start with a nondeterminist method in order to reduce the searchspace to a region where the global minima is located ..."
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Abstract. In this chapter we present a hybrid approach to optimization problems, where we use deterministic and stochastic/evolutionary optimization algorithms. The basic idea is to start with a nondeterminist method in order to reduce the searchspace to a region where the global minima is located. At this point an automatic switch to a deterministic method is performed in order to obtain a rapid convergence to the global extreme. A revision of some wellknown optimization algorithms is presented, followed by a comparison among the different optimization techniques and the application of the hybrid method to several mathematical functions having multiple extrema. Key words: optimization, hybrid methods, search algorithms, evolutionary optimization 1
This is a revised version of manuscript no. MPP 23364. Send all correspondence to:
"... This paper presents a numerical procedure to reduce and possibly control the natural convection effects in a cavity filled with a molten material by applying an external electric field whose intensity and spatial distributions are obtained by the use of a hybrid optimizer. In the case of steady elec ..."
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This paper presents a numerical procedure to reduce and possibly control the natural convection effects in a cavity filled with a molten material by applying an external electric field whose intensity and spatial distributions are obtained by the use of a hybrid optimizer. In the case of steady electrohydrodynamics (EHD), the flowfield of electrically charged particles in a solidifying melt is influenced by an externally applied electric field while the existence of any magnetic field is neglected. Solidification front shape, distribution of the charged particles in the accrued solid, and the amount of accrued solid phase in such processes can be influenced by an appropriate distribution and orientation of the electric field. The transient NavierStokes and Maxwell equations were discretized using the finite volume method in a generalized curvilinear nonorthogonal coordinate system. For the phase change problems, we used the enthalpy method. Variation of intensities of electric potentials on the electrodes along the boundaries of the cavity were described using Bsplines. The inverse problem was then formulated to find the electric boundary conditions (the coefficients of the Bsplines) in such a way that the gradients of temperature along the horizontal direction are
INCREMENTAL IDENTIFICATION OF TRANSPORT COEFFICIENTS IN CONVECTIONDIFFUSION SYSTEMS
"... Abstract. In this paper, an incremental approach for the identification of a model for transport coefficients in convectiondiffusion systems on the basis of highresolution measurement data is presented. The transport is represented by a convection term with known convective velocity and by a diff ..."
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Abstract. In this paper, an incremental approach for the identification of a model for transport coefficients in convectiondiffusion systems on the basis of highresolution measurement data is presented. The transport is represented by a convection term with known convective velocity and by a diffusion term with an unknown, generally statedependent transport coefficient. The identification of the transport model for this transport coefficient constitutes an illposed nonlinear inverse problem. We present a novel decomposition approach in which this inverse problem is split into a sequence of inverse subproblems. In the first identification step of this incremental approach a source is estimated by solving an affinelinear inverse problem by means of the conjugate gradient method. In the second identification step a nonlinear inverse problem has to be solved in order to reconstruct a transport coefficient. A Newtontype method using the conjugate gradient method in its inner iteration is used to solve this nonlinear inverse problem of coefficient estimation. Finally, in the third identification step a transport model structure is proposed and identified on the basis of the modelfree transport coefficient reconstructed in the two previous steps. The illposedness of each inverse problem is examined by using artificially perturbed transient simulation data and appropriate regularization techniques. The identification methodology is illustrated for a threedimensional convectiondiffusion equation which has its origin in the modeling and simulation of energy transport in a laminar wavy film flow. Key words. Modeling, identification, transport, convectiondiffusion equation, inverse problem, regularization, parameter estimation.
AeroThermalElasticityMaterials Optimization of . . .
, 2004
"... The first lecture in this twolecture sequence provides background and general concepts. The second lecture provides practical examples. The objective of these two lectures is to provide a modular design optimization tool description that will take into account interaction of the hot gas flowfield, ..."
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The first lecture in this twolecture sequence provides background and general concepts. The second lecture provides practical examples. The objective of these two lectures is to provide a modular design optimization tool description that will take into account interaction of the hot gas flowfield, heat transfer in the blade material, internal coolant flowfield, stresses and deformations of the blades in a multistage axial gas turbine. These methodologies should result in a multidisciplinary design optimization tool for the entire system (a multistage turbine) rather than a design method for an isolated component (a single turbomachinery blade). In order to make the entire design methodology computationally economical, the proposed method should utilize a combination of fast approximate models as well as highly accurate and detailed complete models for aerodynamics, heat transfer, and thermoelasticity. These calculations should be performed using parallel computing. The byproducts of the optimization are shapes, optimized average surface roughness of the coolant passages, coolant bulk temperature variation, coolant bulk pressure variation and pressure losses in the coolant passages, and surface convective heat transfer coefficients in each of the coolant passages.