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Publications (10 of 96) Show all publications
Mousavi, A., Berggren, M., Hägg, L. & Wadbro, E. (2024). Topology optimization of a waveguide acoustic black hole for enhanced wave focusing. Journal of the Acoustical Society of America, 155(1), 742-756
Open this publication in new window or tab >>Topology optimization of a waveguide acoustic black hole for enhanced wave focusing
2024 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 155, no 1, p. 742-756Article in journal (Refereed) Published
Abstract [en]

The waveguide acoustic black hole (WAB) effect is a promising approach for controlling wave propagation in various applications, especially for attenuating sound waves. While the wave-focusing effect of structural acoustic black holes has found widespread applications, the classical ribbed design of waveguide acoustic black holes (WABs) acts more as a resonance absorber than a true wave-focusing device. In this study, we employ a computational design optimization approach to achieve a conceptual design of a WAB with enhanced wave-focusing properties. We investigate the influence of viscothermal boundary losses on the optimization process by formulating two distinct cases: one neglecting viscothermal losses and the other incorporating these losses using a recently developed material distribution topology optimization technique. We compare the performance of optimized designs in these two cases with that of the classical ribbed design. Simulations using linearized compressible Navier–Stokes equations are conducted to evaluate the wave-focusing performance of these different designs. The results reveal that considering viscothermal losses in the design optimization process leads to superior wave-focusing capabilities, highlighting the significance of incorporating these losses in the design approach. This study contributes to the advancement of WAB design and opens up new possibilities for its applications in various fields.

Place, publisher, year, edition, pages
Acoustical Society of America, 2024
Keywords
Acoustical properties, Acoustic phenomena, Acoustic waves, Black holes, Finite-element analysis, Mathematical optimization, Boundary integral methods, Optimization problems, Liquid solid interfaces, Navier Stokes equations
National Category
Computer Sciences
Identifiers
urn:nbn:se:umu:diva-214110 (URN)10.1121/10.0024470 (DOI)001153140300001 ()38284824 (PubMedID)2-s2.0-85183806282 (Scopus ID)
Funder
eSSENCE - An eScience CollaborationSwedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Note

Originally included in thesis in manuscript form. 

Available from: 2023-09-05 Created: 2023-09-05 Last updated: 2024-02-14Bibliographically approved
Hosseini, S. A., Wadbro, E., Ngoc Do, D. & Lindroos, O. (2023). A scenario-based metaheuristic and optimization framework for cost-effective machine-trail network design in forestry. Computers and Electronics in Agriculture, 212, Article ID 108059.
Open this publication in new window or tab >>A scenario-based metaheuristic and optimization framework for cost-effective machine-trail network design in forestry
2023 (English)In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 212, article id 108059Article in journal (Refereed) Published
Abstract [en]

Designing an optimal machine trail network is a complex locational problem that requires an understanding of different machines’ operations and terrain features as well as the trade-offs between various objectives. With the overall goal to minimize the operational costs of the logging operation, this paper proposes a mathematical optimization model for the trail network design problem and a greedy heuristic method based on different randomized search scenarios aiming to find the optimal location of machine trails —with potential to reduce negative environmental impact. The network is designed so that all trees can be reached and adapted to how the machines can maneuver while considering the terrain elevation's influence. To examine the effectiveness and practical performance of the heuristic and the optimization model, it was applied in a case study on four harvest units with different topologies and shapes. The computational experiments show that the heuristic can generate solutions that outperform the solutions corresponding to conventional, manual designs within practical time limits for operational planning. Moreover, to highlight certain features of the heuristic and the parameter settings’ effect on its performance, we present an extensive computational sensitivity analysis.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Algorithm design, Forest machine-trail optimization, Heuristic, GRASP, Transportation
National Category
Computer Sciences
Identifiers
urn:nbn:se:umu:diva-212483 (URN)10.1016/j.compag.2023.108059 (DOI)2-s2.0-85165537328 (Scopus ID)
Funder
Vinnova, 2018-03344Swedish Research Council Formas, 942-2015-62
Available from: 2023-08-03 Created: 2023-08-03 Last updated: 2023-08-03Bibliographically approved
Mousavi, A., Berggren, M. & Wadbro, E. (2023). Extending material distribution topology optimization to boundary-effect-dominated problems with applications in viscothermal acoustics. Materials & design, 234, Article ID 112302.
Open this publication in new window or tab >>Extending material distribution topology optimization to boundary-effect-dominated problems with applications in viscothermal acoustics
2023 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 234, article id 112302Article in journal (Other academic) Published
Abstract [en]

A new formulation is presented that extends the material distribution topology optimization method to address boundary-effect-dominated problems, where specific boundary conditions need to be imposed at solid–fluid interfaces. As an example of such a problem, we focus on the design of acoustic structures with significant viscous and thermal boundary losses. In various acoustic applications, especially for acoustically small devices, the main portion of viscothermal dissipation occurs in the so-called acoustic boundary layer. One way of accounting for these losses is through a generalized acoustic impedance boundary condition. This boundary condition has previously been proven to provide accurate results with significantly less computational effort compared to Navier–Stokes simulations. To incorporate this boundary condition into the optimization process at the solid–fluid interface, we introduce a mapping of jumps in densities between neighboring elements to an edge-based boundary indicator function. Two axisymmetric case studies demonstrate the effectiveness of the proposed design optimization method. In the first case, we enhance the absorption performance of a Helmholtz resonator in a narrow range of frequencies. In the second case, we consider an acoustically larger problem and achieve an almost-perfect broadband absorption. Our findings underscore the potential of our approach for the design optimization of boundary-effect-dominated problems.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Design optimization, Topology optimization, Helmholtz equation, Acoustic boundary layer, Absorption coefficient, Broadband absorption
National Category
Computer Sciences
Identifiers
urn:nbn:se:umu:diva-214109 (URN)10.1016/j.matdes.2023.112302 (DOI)2-s2.0-85171333478 (Scopus ID)
Funder
eSSENCE - An eScience CollaborationSwedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Note

Originally included in thesis in manuscript form. 

Available from: 2023-09-05 Created: 2023-09-05 Last updated: 2023-09-28Bibliographically approved
Bokhari, A. H., Berggren, M., Noreland, D. & Wadbro, E. (2023). Loudspeaker cabinet design by topology optimization. Scientific Reports, 13(1), Article ID 21248.
Open this publication in new window or tab >>Loudspeaker cabinet design by topology optimization
2023 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 21248Article in journal (Refereed) Published
Abstract [en]

Using material distribution-based topology optimization, we optimize the bandpass design of a loudspeaker cabinet targeting low frequencies. The objective is to maximize the loudspeaker’s output power for a single frequency as well as a range of frequencies. To model the loudspeaker’s performance, we combine a linear electromechanical transducer model with a computationally efficient hybrid 2D–3D model for sound propagation. The adjoint variable approach computes the gradients of the objective function with respect to the design variables, and the Method of Moving Asymptotes (MMA) solves the topology optimization problem. To manage intermediate values of the material indicator function, a quadratic penalty is added to the objective function, and a non-linear filter is used to obtain a mesh independent design. By carefully selecting the target frequency range, we can guide the optimization algorithm to successfully generate a loudspeaker design with the required bandpass character. To the best of our knowledge, this study constitutes the first successful attempt to design the interior structure of a loudspeaker cabinet using topology optimization.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Applied Mechanics
Identifiers
urn:nbn:se:umu:diva-218076 (URN)10.1038/s41598-023-46170-4 (DOI)2-s2.0-85178334680 (Scopus ID)
Funder
Swedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Available from: 2023-12-19 Created: 2023-12-19 Last updated: 2023-12-19Bibliographically approved
Nobis, H., Schlatter, P., Wadbro, E., Berggren, M. & Henningson, D. S. (2023). Modal laminar–turbulent transition delay by means of topology optimization of superhydrophobic surfaces. Computer Methods in Applied Mechanics and Engineering, 403, Article ID 115721.
Open this publication in new window or tab >>Modal laminar–turbulent transition delay by means of topology optimization of superhydrophobic surfaces
Show others...
2023 (English)In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 403, article id 115721Article in journal (Refereed) Published
Abstract [en]

When submerged under a liquid, the microstructure of a SuperHydrophobic Surface (SHS) traps a lubricating layer of gas pockets, which has been seen to reduce the skin friction of the overlying liquid flow in both laminar and turbulent regimes. More recently, spatially homogeneous SHS have also been shown to delay laminar–turbulent transition in channel flows, where transition is triggered by modal mechanisms. In this study, we investigate, by means of topology optimization, whether a spatially inhomogeneous SHS can be designed to further delay transition in channel flows. Unsteady direct numerical simulations are conducted using the spectral element method in a 3D periodic wall-bounded channel. The effect of the SHS is modelled using a partial slip length on the walls, forming a 2D periodic optimization domain. Following a density-based approach, the optimization procedure uses the adjoint-variable method to compute gradients and a checkpointing strategy to reduce storage requirements. This methodology is adapted to optimizing over an ensemble of initial perturbations. This study presents the first application of topology optimization to laminar–turbulent transition. We show that this method can design surfaces that delay transition significantly compared to a homogeneous counterpart, by inhibiting the growth of secondary instability modes. By optimizing over an ensemble of streamwise phase-shifted perturbations, designs have been found with comparable mean transition time and lower variance.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Channel flow, Direct numerical simulations, Laminar–turbulent transition, Spectral element method, Super-hydrophobic surfaces, Topology optimization
National Category
Applied Mechanics Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-201199 (URN)10.1016/j.cma.2022.115721 (DOI)000906896000009 ()2-s2.0-85141501653 (Scopus ID)
Funder
Swedish Research Council, 2016-06119Swedish Research Council, 2019-04339
Available from: 2022-12-15 Created: 2022-12-15 Last updated: 2023-09-05Bibliographically approved
Araujo-Cabarcas, J. C., Engström, C. & Wadbro, E. (2023). Shape optimization for the strong routing of light in periodic diffraction gratings. Journal of Computational Physics, 472, Article ID 111684.
Open this publication in new window or tab >>Shape optimization for the strong routing of light in periodic diffraction gratings
2023 (English)In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 472, article id 111684Article in journal (Refereed) Published
Abstract [en]

In the quest for the development of faster and more reliable technologies, the ability to control the propagation, confinement, and emission of light has become crucial. The design of guide mode resonators and perfect absorbers has proven to be of fundamental importance. In this project, we consider the shape optimization of a periodic dielectric slab aiming at efficient directional routing of light to reproduce similar features of a guide mode resonator. For this, the design objective is to maximize the routing efficiency of an incoming wave. That is, the goal is to promote wave propagation along the periodic slab. A Helmholtz problem with a piecewise constant and periodic refractive index medium models the wave propagation, and an accurate Robin-to-Robin map models an exterior domain. We propose an optimal design strategy that consists of representing the dielectric interface by a finite Fourier formula and using its coefficients as the design variables. Moreover, we use a high order finite element (FE) discretization combined with a bilinear Transfinite Interpolation formula. This setting admits explicit differentiation with respect to the design variables, from where an exact discrete adjoint method computes the sensitivities. We show in detail how the sensitivities are obtained in the quasi-periodic discrete setting. The design strategy employs gradient-based numerical optimization, which consists of a BFGS quasi-Newton method with backtracking line search. As a test case example, we present results for the optimization of a so-called single port perfect absorber. We test our strategy for a variety of incoming wave angles and different polarizations. In all cases, we efficiently reach designs featuring high routing efficiencies that satisfy the required criteria.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Diffraction grating, Helmholtz problem, Light routing, Scattering problem, Shape optimization
National Category
Computational Mathematics
Identifiers
urn:nbn:se:umu:diva-200659 (URN)10.1016/j.jcp.2022.111684 (DOI)000879217600002 ()2-s2.0-85140226291 (Scopus ID)
Funder
The Kempe Foundations, SMK-1857eSSENCE - An eScience CollaborationSwedish Research Council, 2021-04537
Available from: 2022-11-07 Created: 2022-11-07 Last updated: 2023-09-05Bibliographically approved
Bokhari, A. H., Hassan, E. & Wadbro, E. (2023). Topology optimization of microwave frequency dividing multiplexers. Structural and multidisciplinary optimization (Print), 66, Article ID 106.
Open this publication in new window or tab >>Topology optimization of microwave frequency dividing multiplexers
2023 (English)In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 66, article id 106Article in journal (Refereed) Published
Abstract [en]

We use material-distribution-based topology optimization to design a three-port frequency dividing multiplexer at microwave frequencies. That is, by placing a good electric conductor inside the design domain, we aim to design a passive device that splits the incoming signal's frequencies into two frequency bands and transmits them to their respective output ports. The Helmholtz equation is used to model the time-harmonic wave propagation problem. We use the finite element method to solve the governing equation. The adjoint variable method provides the required gradients, and we solve the topology optimization problem using Svanberg's MMA algorithm. In this study, we present a technique for modeling the distribution of a good electric conductor within the design domain. In addition, we derive a power balance expression, which aids in formulating a series of three objective functions. In each successive objective function, we add more information and evaluate its impact on the results. The results show that by selecting a suitable objective function, we achieve more than 93.7 % transmission for both the frequency bands. Moreover, the numerical experiments suggest that the optimization problem is self penalized and is sensitive to the initial design.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
multiplexer, electromagnetic, microwave, topology optimization, material-distribution method
National Category
Computational Mathematics Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:umu:diva-193413 (URN)10.1007/s00158-023-03561-5 (DOI)000984353000001 ()2-s2.0-85153201085 (Scopus ID)
Funder
eSSENCE - An eScience Collaboration
Note

Originally included in manuscript form in thesis with title: "Topology optimization of microwave frequency dividing multiplexer". 

Available from: 2022-03-31 Created: 2022-03-31 Last updated: 2023-11-02Bibliographically approved
Hosseini, S. A. & Wadbro, E. (2022). A hybrid greedy randomized heuristic for designing uncertain transport network layout. Expert systems with applications, 190, Article ID 116151.
Open this publication in new window or tab >>A hybrid greedy randomized heuristic for designing uncertain transport network layout
2022 (English)In: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 190, article id 116151Article in journal (Refereed) Published
Abstract [en]

The foundations of efficient management are laid on transport networks in various scientific and industrial fields. Nonetheless, establishing an optimum transport network design (TND) is complicated due to uncertainty in the operating environment. As a result, an uncertain network may be a more realistic representation of an actual transport network. The present study deals with an uncertain TND problem in which uncertain programming and the greedy randomized adaptive search procedure (GRASP) are used to develop an original optimization framework and propose a solution technique for obtaining cost-efficient designs. To this end, we originally develop the concept of α-shortest cycle (α-SC) employing the pessimistic value criterion, given a user-defined predesignated confidence level α. Employing this concept and the operational law of uncertain programming, a new auxiliary chance-constrained programming model is established for the uncertain TND problem, and we prove the existence of an equivalence relation between TNDs in an uncertain network and those in an auxiliary deterministic network. Specifically, we articulate how to obtain the uncertainty distribution of the overall optimal uncertain network's design cost. After all, the effectiveness and practical performance of the heuristic and optimization model is illustrated by adopting samples with different topology from a case study to show how our approach work in realistic networks and to highlight some of the heuristic's features.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Heuristics, Network design, Operations research, Transportation, Uncertain programming
National Category
Computer Sciences
Identifiers
urn:nbn:se:umu:diva-189611 (URN)10.1016/j.eswa.2021.116151 (DOI)000720621200001 ()2-s2.0-85118736471 (Scopus ID)
Funder
Mistra - The Swedish Foundation for Strategic Environmental ResearchVinnova, 2018-03344Swedish Research Council Formas, 942-2015-62
Available from: 2021-11-17 Created: 2021-11-17 Last updated: 2023-09-05Bibliographically approved
Mousavi, A., Berggren, M. & Wadbro, E. (2022). How the waveguide acoustic black hole works: A study of possible damping mechanisms. Journal of the Acoustical Society of America, 151(6), 4279-4290
Open this publication in new window or tab >>How the waveguide acoustic black hole works: A study of possible damping mechanisms
2022 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 151, no 6, p. 4279-4290Article in journal (Refereed) Published
Abstract [en]

The acoustic black hole (ABH) effect in waveguides is studied using frequency-domain finite element simulations of a cylindrical waveguide with an embedded ABH termination composed of retarding rings. This design is adopted from an experimental study in the literature, which surprisingly showed, contrary to the structural counterpart, that the addition of damping material to the end of the waveguide does not significantly reduce the reflection coefficient any further. To investigate this unexpected behavior, we model different damping mechanisms involved in the attenuation of sound waves in this setup. A sequence of computed pressure distributions indicates occurrences of frequency-dependent resonances in the device. The axial position of the cavity where the resonance occurs can be predicted by a more elaborate wall admittance model than the one that was initially used to study and design ABHs. The results of our simulations show that at higher frequencies, the visco-thermal losses and the damping material added to the end of the setup do not contribute significantly to the performance of the device. Our results suggest that the primary source of damping, responsible for the low reflection coefficients at higher frequencies, is local absorption effects at the outer surface of the cylinder.

Keywords
Acoustic black hole, Finite element method, Helmholtz equation
National Category
Fluid Mechanics and Acoustics Applied Mechanics Computational Mathematics
Identifiers
urn:nbn:se:umu:diva-198676 (URN)10.1121/10.0011788 (DOI)000818623100001 ()35778217 (PubMedID)2-s2.0-85133707077 (Scopus ID)
Funder
Swedish Research Council, Swedish Research Council
Available from: 2022-08-17 Created: 2022-08-17 Last updated: 2023-09-05Bibliographically approved
Bokhari, A. H. & Wadbro, E. (2022). Sensitivity analysis of a coupled plasmonic problem.
Open this publication in new window or tab >>Sensitivity analysis of a coupled plasmonic problem
2022 (English)Report (Other academic)
Abstract [en]

In material distribution-based topology optimization, we place material inside a design domain to extremize an objective function. The optimization problem is solved using a gradient-based algorithm. An efficient way to compute the gradients is to use the adjoint method. This study performs the sensitivity analysis of a coupled plasmonic problem using the adjoint method. More precisely, a TE-polarized Helmholtz equation is coupled to a Poisson equation. The sensitivity analysis of the coupled plasmonic problem poses some challenges stemming from the complex solution of the plasmonic problem. Therefore, we first consider a model problem whose structure is similar to the main problem in some ways but is simpler to study. After examining the model problem, we perform the sensitivity analysis of the coupled plasmonic problem, highlighting key differences between the two problems.

Publisher
p. 21
Series
Report / UMINF, ISSN 0348-0542 ; 22.04
Keywords
metallic antenna, plasmonics, sensitivity analysis, adjoint method, material distribution
National Category
Nano Technology Computational Mathematics
Identifiers
urn:nbn:se:umu:diva-193443 (URN)
Available from: 2022-04-01 Created: 2022-04-01 Last updated: 2022-04-01Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8704-9584

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