Acoustic wave propagation in equivalent fluid macroscopically inhomogeneous materials

Cieszko, M.; Drelich, Radosław; Pakuła, Michał

doi:10.1121/1.4756949

Cited by 10 publications

(2 citation statements)

References 22 publications

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“…Together these results highlight the importance of defining the edges of the bone layer as a discontinuous, rather than smoothly varying, interface. This is likely because, when acoustic properties vary over a finite distance (rather than forming sharp, discontinuous interfaces), the resulting reflection and transmission coefficients demonstrate frequency dependent behaviour determined by the spatial rate of change of acoustic properties (Cieszko et al 2012). Ultrasound with wavelengths close to the spatial extent of the smoothly varying interface (or shorter) experience reduced reflection and increased transmission, consistent with the results shown here.…”

Section: Discussionsupporting

confidence: 83%

The effects of image homogenisation on simulated transcranial ultrasound propagation

et al. 2018

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Transcranial transmission of ultrasound is increasingly used in a variety of clinical and research applications, including high intensity ablation, opening the blood brain barrier, and neural stimulation. Numerical simulations of ultrasound propagation in the head are used to enable effective transcranial focusing and predict intracranial fields. Such simulations require maps of the acoustic properties of the head, which can be derived from clinical CT images. However, the spatial resolution of these images is typically coarser than the scale of heterogeneities within the skull bone, which are known to exert a major influence on ultrasound propagation. In the present work, the impact of image related homogenisation on transcranial transmission from a single element transducer is examined using a dataset of co-registered clinical resolution CT and micro-CT images of skull sections. Reference acoustic property maps are derived from micro-CT images of cortical bone tissue. The influence of imaging resolution is examined by progressively downsampling the segmented acoustic property maps, and through comparison with maps derived from co-registered clinical CT images. The influence of different methods of segmenting the bone volume from the clinical CT images, and for resampling the clinical and micro-CT data are also examined. Image related homogenisation is demonstrated to have a substantial effect on the transcranial transmission of ultrasound, resulting in underestimations of simulated transmission loss and time-of flight. Effects on time-of flight are due to the loss of the internal scattering microstructure of the skull, while changes in transmitted ultrasound amplitude are due to both loss of microstructure and other smoothing effects. Inflating the simulated attenuation coefficient of the skull layer reduces the error in transmitted pressure amplitude to around 40%, however this is unable to correct fully for errors in time of flight and the pressure distribution of the transmitted field.

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Section: Discussionsupporting

confidence: 83%

The effects of image homogenisation on simulated transcranial ultrasound propagation

et al. 2018

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“…It is the socalled Johnson-Champoux-Allard model [6][7][8][9][10][11] or its tuned-up versions with enhancements proposed by Pride 12,13 or Lafarge. 14 Recently, the acoustic wave propagation in macroscopically inhomogeneous materials using the equivalent fluid approach was also studied by Cieszko et al 15 In general, acoustics of granular media with open porosity can be modelled in the same or very similar way as other porous or fibrous materials. For example, Attenborough 16 proposed a model that predicts the acoustical characteristics of rigid fibrous absorbents and granular materials from five parameters (porosity, flow resistivity, tortuosity, steady flow shape factor, and dynamic shape factor).…”

Section: Introductionmentioning

confidence: 99%

Microstructure-based calculations and experimental results for sound absorbing porous layers of randomly packed rigid spherical beads

Zieliński

2014

Journal of Applied Physics

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Acoustics of stiff porous media with open porosity can be very effectively modelled using the so-called Johnson-Champoux-Allard-Pride-Lafarge model for sound absorbing porous media with rigid frame. It is an advanced semi-phenomenological model with eight parameters, namely, the total porosity, the viscous permeability and its thermal analogue, the tortuosity, two characteristic lengths (one specific for viscous forces, the other for thermal effects), and finally, viscous and thermal tortuosities at the frequency limit of 0 Hz. Most of these parameters can be measured directly, however, to this end specific equipment is required different for various parameters. Moreover, some parameters are difficult to determine. This is one of several reasons for the so-called multiscale approach, where the parameters are computed from specific finite-element analyses based on some realistic geometric representations of the actual microstructure of porous material. Such approach is presented and validated for layers made up of loosely packed small identical rigid spheres. The sound absorption of such layers was measured experimentally in the impedance tube using the so-called two-microphone transfer function method. The layers are characterised by open porosity and semi-regular microstructure: the identical spheres are loosely packed by random pouring and mixing under the gravity force inside the impedance tubes of various size. Therefore, the regular sphere packings were used to generate Representative Volume Elements suitable for calculations at the micro-scale level. These packings involve only one, two, or four spheres so that the three-dimensional finite-element calculations specific for viscous, thermal, and tortuous effects are feasible. In the proposed geometric packings, the spheres were slightly shifted in order to achieve the correct value of total porosity which was precisely estimated for the layers tested experimentally. Finally, in this paper some results based on the self-consistent estimates are also provided. V C 2014 AIP Publishing LLC. [http://dx.

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Equations and fundamental characteristics of compressional waves propagating in fluid-saturated porous materials

Cieszko

Kubik

2022

International Journal of Engineering Science

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Acoustic wave propagation in equivalent fluid macroscopically inhomogeneous materials

Cited by 10 publications

References 22 publications

The effects of image homogenisation on simulated transcranial ultrasound propagation

The effects of image homogenisation on simulated transcranial ultrasound propagation

Microstructure-based calculations and experimental results for sound absorbing porous layers of randomly packed rigid spherical beads

Equations and fundamental characteristics of compressional waves propagating in fluid-saturated porous materials

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