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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
Åpne denne publikasjonen i ny fane eller vindu >>Topology optimization of a waveguide acoustic black hole for enhanced wave focusing
2024 (engelsk)Inngår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 155, nr 1, s. 742-756Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Acoustical Society of America, 2024
Emneord
Acoustical properties, Acoustic phenomena, Acoustic waves, Black holes, Finite-element analysis, Mathematical optimization, Boundary integral methods, Optimization problems, Liquid solid interfaces, Navier Stokes equations
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-214110 (URN)10.1121/10.0024470 (DOI)001153140300001 ()38284824 (PubMedID)2-s2.0-85183806282 (Scopus ID)
Forskningsfinansiär
eSSENCE - An eScience CollaborationSwedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Merknad

Originally included in thesis in manuscript form. 

Tilgjengelig fra: 2023-09-05 Laget: 2023-09-05 Sist oppdatert: 2024-02-14bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Extending material distribution topology optimization to boundary-effect-dominated problems with applications in viscothermal acoustics
2023 (engelsk)Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 234, artikkel-id 112302Artikkel i tidsskrift (Annet vitenskapelig) 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.

sted, utgiver, år, opplag, sider
Elsevier, 2023
Emneord
Design optimization, Topology optimization, Helmholtz equation, Acoustic boundary layer, Absorption coefficient, Broadband absorption
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-214109 (URN)10.1016/j.matdes.2023.112302 (DOI)2-s2.0-85171333478 (Scopus ID)
Forskningsfinansiär
eSSENCE - An eScience CollaborationSwedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Merknad

Originally included in thesis in manuscript form. 

Tilgjengelig fra: 2023-09-05 Laget: 2023-09-05 Sist oppdatert: 2023-09-28bibliografisk kontrollert
Bokhari, A. H., Berggren, M., Noreland, D. & Wadbro, E. (2023). Loudspeaker cabinet design by topology optimization. Scientific Reports, 13(1), Article ID 21248.
Åpne denne publikasjonen i ny fane eller vindu >>Loudspeaker cabinet design by topology optimization
2023 (engelsk)Inngår i: Scientific Reports, E-ISSN 2045-2322, Vol. 13, nr 1, artikkel-id 21248Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Springer Nature, 2023
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-218076 (URN)10.1038/s41598-023-46170-4 (DOI)2-s2.0-85178334680 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2018-03546Swedish Research Council, 2022-03783
Tilgjengelig fra: 2023-12-19 Laget: 2023-12-19 Sist oppdatert: 2023-12-19bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Modal laminar–turbulent transition delay by means of topology optimization of superhydrophobic surfaces
Vise andre…
2023 (engelsk)Inngår i: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 403, artikkel-id 115721Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Elsevier, 2023
Emneord
Channel flow, Direct numerical simulations, Laminar–turbulent transition, Spectral element method, Super-hydrophobic surfaces, Topology optimization
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-201199 (URN)10.1016/j.cma.2022.115721 (DOI)000906896000009 ()2-s2.0-85141501653 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2016-06119Swedish Research Council, 2019-04339
Tilgjengelig fra: 2022-12-15 Laget: 2022-12-15 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Nobis, H., Schlatter, P., Wadbro, E., Berggren, M. & Henningson, D. S. (2023). Topology optimization of Superhydrophobic Surfaces to delay spatially developing modal laminar–turbulent transition. International Journal of Heat and Fluid Flow, 104, Article ID 109231.
Åpne denne publikasjonen i ny fane eller vindu >>Topology optimization of Superhydrophobic Surfaces to delay spatially developing modal laminar–turbulent transition
Vise andre…
2023 (engelsk)Inngår i: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 104, artikkel-id 109231Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Super-Hydrophobic Surfaces (SHSs) have been shown to reduce skin friction of an overlying fluid as a consequence of gas pockets trapped within the surface's microstructure. More recently, they have also been shown capable of delaying laminar–turbulent transition. This article investigates the applicability of topology optimization in designing the macroscopic layout of SHSs in a channel that are able to further delay K-type transition in a spatial setting. Unsteady direct numerical simulations are performed to simulate the transition scenario. This is coupled with adjoint–based sensitivity analysis and gradient based optimization. The optimized designs found through this procedure are capable of moving the transition location further downstream compared to a homogeneous counterpart by inhibiting the growth of secondary instability modes. This article provides the first application of topology optimization to a spatially developing transition scenario.

sted, utgiver, år, opplag, sider
Elsevier, 2023
Emneord
Direct numerical simulations, Laminar–turbulent transition, Superhydrophobic Surfaces, Topology optimization
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-217429 (URN)10.1016/j.ijheatfluidflow.2023.109231 (DOI)2-s2.0-85177193679 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2019-04339Swedish Research Council, 2016-06119eSSENCE - An eScience Collaboration
Tilgjengelig fra: 2023-12-04 Laget: 2023-12-04 Sist oppdatert: 2023-12-04bibliografisk kontrollert
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
Åpne denne publikasjonen i ny fane eller vindu >>How the waveguide acoustic black hole works: A study of possible damping mechanisms
2022 (engelsk)Inngår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 151, nr 6, s. 4279-4290Artikkel i tidsskrift (Fagfellevurdert) 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.

Emneord
Acoustic black hole, Finite element method, Helmholtz equation
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-198676 (URN)10.1121/10.0011788 (DOI)000818623100001 ()35778217 (PubMedID)2-s2.0-85133707077 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, Swedish Research Council
Tilgjengelig fra: 2022-08-17 Laget: 2022-08-17 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Nobis, H., Schlatter, P., Wadbro, E., Berggren, M. & Henningson, D. S. (2022). Topology optimization of unsteady flows using the spectral element method. Computers & Fluids, 239, Article ID 105387.
Åpne denne publikasjonen i ny fane eller vindu >>Topology optimization of unsteady flows using the spectral element method
Vise andre…
2022 (engelsk)Inngår i: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 239, artikkel-id 105387Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We investigate the applicability of a high-order Spectral Element Method (SEM) to density based topology optimization of unsteady flows in two dimensions. Direct Numerical Simulations (DNS) are conducted relying on Brinkman penalization to describe the presence of solid within the domain. The optimization procedure uses the adjoint-variable method to compute gradients and a checkpointing strategy to reduce storage requirements. A nonlinear filtering strategy is used to both enforce a minimum length scale and to provide smoothing across the fluid–solid interface, preventing Gibbs oscillations. This method has been successfully applied to the design of a channel bend and an oscillating pump, and demonstrates good agreement with body fitted meshes. The precise design of the pump is shown to depend on the initial material distribution. However, the underlying topology and pumping mechanism is the same. The effect of a minimum length scale has been studied, revealing it to be a necessary regularization constraint for the oscillating pump to produce meaningful designs. The combination of SEM and density based optimization offer some unique challenges which are addressed and discussed, namely a lack of explicit boundary tracking exacerbated by the interface smoothing. Nevertheless, SEM can achieve equivalent levels of precision to traditional finite element methods, while requiring fewer degrees of freedom. Hence, the use of SEM addresses the two major bottlenecks associated with optimizing unsteady flows: computation cost and data storage.

sted, utgiver, år, opplag, sider
Elsevier, 2022
Emneord
Direct numerical simulations, Length scale control, Non-linear filtering, Spectral element method, Topology optimization, Unsteady
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-193403 (URN)10.1016/j.compfluid.2022.105387 (DOI)000793263500001 ()2-s2.0-85126644608 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2019-04339eSSENCE - An eScience Collaboration
Tilgjengelig fra: 2022-03-31 Laget: 2022-03-31 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Bokhari, A. H., Berggren, M., Noreland, D. & Wadbro, E. (2021). A computationally efficient hybrid 2D–3D subwoofer model. Scientific Reports, 11, Article ID 255.
Åpne denne publikasjonen i ny fane eller vindu >>A computationally efficient hybrid 2D–3D subwoofer model
2021 (engelsk)Inngår i: Scientific Reports, E-ISSN 2045-2322, Vol. 11, artikkel-id 255Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

sted, utgiver, år, opplag, sider
Nature Publishing Group, 2021
Emneord
Acoustics, Applied Mathematics, Computational Science
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-178326 (URN)10.1038/s41598-020-80092-9 (DOI)000634380400001 ()2-s2.0-85098947980 (Scopus ID)
Forskningsfinansiär
eSSENCE - An eScience CollaborationSwedish National Infrastructure for Computing (SNIC)
Tilgjengelig fra: 2021-01-09 Laget: 2021-01-09 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Asan, N. B., Hassan, E., Perez, M. D., Joseph, L., Berggren, M., Voigt, T. & Augustine, R. (2021). Fat-IntraBody Communication at 5.8 GHz: Verification of Dynamic Body Movement Effects using Computer Simulation and Experiments. IEEE Access, 9, 48429-48445
Åpne denne publikasjonen i ny fane eller vindu >>Fat-IntraBody Communication at 5.8 GHz: Verification of Dynamic Body Movement Effects using Computer Simulation and Experiments
Vise andre…
2021 (engelsk)Inngår i: IEEE Access, E-ISSN 2169-3536, Vol. 9, s. 48429-48445Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper presents numerical modeling and experimental validation of the signal path loss at the 5.8 GHz Industrial, Scientific, and Medical (ISM) band, performed in the context of fat-intrabody communication (fat-IBC), a novel intrabody communication platform using the body-omnipresent fat tissue as the key wave-guiding medium. Such work extends our previous works at 2.0 and 2.4 GHz in the characterization of its performance in other useful frequency range. In addition, this paper also includes studies of both static and dynamic human body movements. In order to provide with a more comprehensive characterization of the communication performance at this frequency, this work focuses on investigating the path loss at different configurations of fat tissue thickness, antenna polarizations, and locations in the fat channel. We bring more realism to the experimental validation by using excised tissues from porcine cadaver as both their fat and muscle tissues have electromagnetic characteristics similar to those of human with respect to current state-of-art artificial phantom models. Moreover, for favorable signal excitation and reception in the fat-IBC model, we used topology optimized waveguide probes. These probes provide an almost flat response in the frequency range from 3.2 to 7.1 GHz which is higher than previous probes and improve the evaluation of the performance of the fat-IBC model. We also discuss various aspects of real-world scenarios by examining different models, particularly homogeneous multilayered skin, fat, and muscle tissue. To study the effect of dynamic body movements, we examine the impact of misalignment, both in space and in wave polarization, between implanted nodes. We show in particular that the use of fat-IBC techniques can be extended up in frequency to a broadband channel at 5.8 GHz.

sted, utgiver, år, opplag, sider
IEEE, 2021
Emneord
Antennas, channel characterization, dielectric properties measurement, Dielectrics, ex-vivo, fat tissue, fat-IBC, Fats, intrabody microwave communication, ISM band, Muscles, path loss, Phantoms, polarization, Probes, Skin, topology optimization
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-182157 (URN)10.1109/ACCESS.2021.3068400 (DOI)000637183300001 ()2-s2.0-85103303855 (Scopus ID)
Forskningsfinansiär
Swedish Foundation for Strategic Research , RIT17-0020EU, Horizon 2020, SINTEC-824984eSSENCE - An eScience Collaboration
Tilgjengelig fra: 2021-04-22 Laget: 2021-04-22 Sist oppdatert: 2021-07-02bibliografisk kontrollert
Mousavi, A., Berggren, M. & Wadbro, E. (2021). On the acoustic black-hole effect in waveguides. Paper presented at ASA 2021, The 180th Meeting of the Acoustical Society of America, Acoustics in Focus, Virtual, June 8-10, 2021. Journal of the Acoustical Society of America, 149(4), Article ID A108.
Åpne denne publikasjonen i ny fane eller vindu >>On the acoustic black-hole effect in waveguides
2021 (engelsk)Inngår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 149, nr 4, artikkel-id A108Artikkel i tidsskrift, Meeting abstract (Fagfellevurdert) Published
Abstract [en]

The acoustic black-hole (ABH) effect is a well-known way of controlling structural vibrations in solid beams and plates. The theory behind this effect is to reduce the velocity of waves by altering the physical properties of the domain according to a power-law profile. For an ideal ABH, this leads to vanishing reflections from the end of the termination. In practice, there will be a truncation in the profile, which leads to some reflections. A well-known way of minimizing this truncation error is to add damping material to the end of the ABH termination.

For a waveguide embedding a set of rings with retarding inner radius according to a power-law profile, the velocity of sound waves tends to zero. However, unlike the structural counterpart, experimental results in the literature show that adding damping material to reduce the truncation error is not effective for waveguides. Here, we present a finite element simulation of the considered cylindrical setup. Our results confirm that the addition of damping material to the end of the waveguide is ineffective while suggesting that the local absorption effects at the lateral surface of the cylinder are a primary source of damping to achieve the ABH effect.

sted, utgiver, år, opplag, sider
Acoustical Society of America (ASA), 2021
Emneord
Acoustic black-hole, finite element method, acoustic waveguide
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-189729 (URN)10.1121/10.0004664 (DOI)
Konferanse
ASA 2021, The 180th Meeting of the Acoustical Society of America, Acoustics in Focus, Virtual, June 8-10, 2021
Tilgjengelig fra: 2021-11-19 Laget: 2021-11-19 Sist oppdatert: 2021-11-22bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-0473-3263