SDDOM 2012 Abstracts


Full Papers
Paper Nr: 3
Title:

Managing Model Fidelity for Efficient Optimization of Antennas using Variable-resolution Electromagnetic Simulations

Authors:

Slawomir Koziel, Stanislav Ogurtsov and Leifur Leifsson

Abstract: Electromagnetic (EM) simulation has become an important tool in the design of contemporary antenna structures. However, accurate simulations of realistic antenna models are expensive and therefore design automation by employing EM solver within an optimization loop may be prohibitive because of its high computational cost. Efficient EM-driven antenna design can be performed using surrogate-based optimization (SBO). A generic approach to construct surrogate models of antennas involves the use of coarse-discretization EM simulations (low-fidelity models). A proper selection of the surrogate model fidelity is a key factor that influences both the performance of the design optimization process and its computational cost. Despite its importance, this issue has not yet been investigated in the literature. Here, we focus on a problem of proper surrogate model management. More specifically, we carry out a numerical study that aims at finding a trade-off between the design cost and reliability of the SBO algorithms. Our considerations are illustrated using several antenna design cases. Furthermore, we demonstrate that the use of multiple models of different fidelity may be beneficial to reduce the design cost while maintaining the robustness of the optimization process.

Paper Nr: 4
Title:

X-FEM based Topological Optimization Method

Authors:

Meisam Abdi, Ian Ashcroft and Ricky Wildman

Abstract: This study presents a new algorithm for structural topological optimization by combining the Extended Finite Element Method (X-FEM) with an evolutionary optimization algorithm. Taking advantage of an isoline design approach for boundary representation in a fixed grid domain, X-FEM can be implemented to obtain more accurate results on the boundary during the optimization process. This approach can produce topologies with clear and smooth boundaries without using a remeshing or a moving mesh algorithm. Also, reanalysing the converged solutions in NASTRAN confirms the high accuracy of the proposed method.

Paper Nr: 5
Title:

Challenges in Applying Optimization in the Design of Continuous Processes - Case: Collaborative Optimizing Design of Pulp Fractionation Process

Authors:

Mika Strömman, Ilkka Seilonen and Kari Koskinen

Abstract: In order to make pulp and paper facility design more effective, simulation and optimization could be used more comprehensively during design. The structure and the operation of the mill should be designed simultaneously, and therefore bi-level multi-objective optimization (BLMOO) is a feasible method. Applying BLMOO in pulp and paper facility design requires changes in business processes of organizations involved. In this research, projects of applying optimizing design in example cases have been followed and a multi-organizational design process is defined. The process is then evaluated by expert interviews.

Paper Nr: 6
Title:

Trawl-door Performance Analysis and Design Optimization with CFD

Authors:

Eirikur Jonsson, Leifur Leifsson and Slawomir Koziel

Abstract: Rising fuel prices and inefficient fishing gear are hampering the fishing industry. In this paper, we present a computational fluid dynamic (CFD) model to analyse the hydrodynamic performance of trawl-doors, which are a major contributor to the high fuel consumption of fishing vessels. Furthermore, we couple the CFD model with an efficient design optimization technique and demonstrate how to redesign the trawl-door shapes for minimum drag at a given lift. The optimization techinique is surrogate-based and employs a coarse discritization CFD model with relaxed convergence criteria. The surrogate model is constructed using the physics based low-fidelity model and space mapping. The CFD model is applied to the analysis of current trawl-door shapes and reveals that they are operated at low efficiency (with lift-to-drag ratios lower than 1), mainly due to massively separated flow. An example design optimization case study reveals that the angle of attack can be reduced significantly by re-positioning and tilting the leading-edge slats. The performance can be improved by as much as 24 times (attaining lift-ro-drag ratios around 24).

Paper Nr: 7
Title:

Transonic Wing Optimization by Variable-resolution Modeling and Space Mapping

Authors:

Eirikur Jonsson, Leifur Leifsson and Slawomir Koziel

Abstract: This paper presents an efficient aerodynamic design optimization methodology for wings in transonic flow. The approach replaces the computationally expensive high-fidelity CFD model in an iterative optimization process with a corrected polynomial approximation model constructed by a cheap low-fidelity CFD model. The output space mapping technique is used to correct the approximation model to yield an accurate predictor of the high-fidelity one. Both CFD models employ the RANS equations with the Spalart-Allmaras turbulence model, but the low-fidelity one uses a coarse mesh resolution and relaxed convergence criteria. Our method is applied to a constrained lift maximization of a rectangular wing at transonic conditions with 3 design variables. The optimized designs are obtained by using 50 low-fidelity CFD model evaluations to set up the approximation model and 7 to 8 high-fidelity model evaluations, equivalent to around 10 high-fidelity CFD model evaluations.

Paper Nr: 8
Title:

Microwave Design Optimization Exploiting Adjoint Sensitivity

Authors:

Slawomir Koziel, Leifur Leifsson and Stanislav Ogurtsov

Abstract: Adjustment of geometry and material parameters is an important step in the design of microwave devices and circuits. Nowadays, it is typically performed using high-fidelity electromagnetic (EM) simulations, which might be a challenging and time consuming process because accurate EM simulations are computationally expensive. In particular, design automation by employing an EM solver in an numerical optimization algorithm may be prohibitive. Recently, adjoint sensitivity techniques become available in commercial EM simulation software packages. This makes it possible to speed up the EM-driven design optimization process either by utilizing the sensitivity information in conventional, gradient-based algorithms or by combining it with surrogate-based approaches. In this paper, we review several recent methods and algorithms for microwave design optimization using adjoint sensitivity. We discuss advantages and disadvantages of these techniques and illustrate them through numerical examples.