Modeling sound propagation in acoustic waveguides using a hybrid numerical method

Kirby, Ray

doi:10.1121/1.2967837

Cited by 48 publications

(49 citation statements)

References 27 publications

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“…One further issue with the hybrid method is the location of planes B and C. This has been discussed in detail for more complicated "obstacles" in acoustic waveguides by Kirby [17] and, in general, it was concluded that one should not locate these planes close to areas in which modal scattering is pronounced. This is because a modal solution often requires a proportionally larger number of modes to accurately represent a complex sound field when compared to the use of a standard finite element discretisation.…”

Section: Uncoated Pipementioning

confidence: 99%

“…For non-uniform discontinuities it is convenient to return to a full finite element discretisation of the defect in order to provide the flexibility to examine arbitrary (but axisymmetric) geometries. Accordingly, a hybrid method is adopted here, which follows the method described by Kirby [17] for acoustic waveguides. The advantage of this method is that it only requires a finite element discretisation of the non uniform defect and so retains the modal expansions within the uniform pipe sections.…”

Section: Hybrid Numerical Methodsmentioning

confidence: 99%

“…This approach has been used by the first author in the study of sound dissipation in acoustic waveguides; for example, Kirby used point collocation [6] and mode matching [16] to enforce acoustic pressure and velocity matching conditions over two area discontinuities, after first finding the eigenmodes using a SAFE method. For non uniform regions, Kirby [16,17] adopts a hybrid method in which a full finite element discretisation of a non uniform section is matched to the surrounding (uniform) duct using either point collocation or mode matching. It is shown in these papers that these methods are potentially very computationally efficient and can be used to study relatively large systems and/or high frequencies.…”

Section: Introductionmentioning

confidence: 99%

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On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

Kirby

Zlatev

Mudge³

2012

Journal of Sound and Vibration

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Long range ultrasonic testing is now a well established method for examining in-service degradation in pipelines. In order to protect pipelines from the surrounding environment it is common for viscoelastic coatings to be applied to the outer surface. These coatings are, however, known to impact on the ability of long range ultrasonic techniques to locate degradation, or defects, within a coated pipe. The coating dissipates sound energy travelling along the pipe, attenuating both the incident and reflected signals making responses from defects difficult to detect. This article aims to investigate the influence of a viscoelastic coating on the ability of long range ultrasonic testing to detect a defect in an axisymmetric pipe. The article focuses on understanding the behaviour of the fundamental torsional mode and quantifying the effect of bitumen coatings on reflection coefficients generated by axisymmetric defects. Reflection coefficients are measured experimentally for coated and uncoated pipes and compared to theoretical predictions generated using numerical mode matching and a hybrid finite element technique. Good agreement between prediction and measurement is observed for uncoated pipes, and it is shown that the theoretical methods presented here are fast and efficient making them suitable for studying long pipe runs. However, when studying coated pipes agreement between theory and prediction is observed to be poor for predictions based on those bulk acoustic properties currently reported in the literature for bitumen. Good agreement is observed only after conducting a parametric study to identify more appropriate values for the bulk acoustic properties. Furthermore, the reflection coefficients obtained for the fundamental torsional mode in a coated pipe show that significant sound attenuation is present over relatively short lengths of coating, thus quantifying those problems commonly encountered with the use of long range ultrasonic testing on coated pipes in the field.3

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Section: Uncoated Pipementioning

confidence: 99%

Section: Hybrid Numerical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

Kirby

Zlatev

Mudge³

2012

Journal of Sound and Vibration

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“…The hybrid method implemented here follows the same general approach as that described by Kirby et al [21,22] for elastic waveguides, see also Kirby [18] and Duan and Kirby [19] for acoustic waveguides. Accordingly, a weak form of Eq.…”

Section: The Hybrid Methodsmentioning

confidence: 99%

“…One possible approach is to find the eigenmodes for a waveguide by directly solving the governing eigenequation. This method is often referred to in the elastodynamic literature as the semi analytic finite element (SAFE) method; however it has also been used in the acoustic waveguide literature where there is no such terminology [18,19]. A hybrid SAFE-FE method was recently applied to elastic wave propagation in a solid cylinder by Benmeddour et al [20].…”

Section: Introductionmentioning

confidence: 99%

A numerical model for the scattering of elastic waves from a non-axisymmetric defect in a pipe

Duan

Kirby

2015

Finite Elements in Analysis and Design

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Ultrasonic guided waves are used in the non-destructive testing of pipelines. This involves launching an elastic wave along the wall of the pipe and then capturing the returning wave scattered by a defect. Numerical study of wave scattering is often computationally expensive because the shortest wavelength is often very small compared to the size of the pipe in the ultrasonic frequency range. Furthermore, the number of the scattered wave modes from a non-axisymmetric defect in the pipe can be large and separation of these modes is difficult in a conventional finite element method. Accordingly, this article presents a model suitable for studying elastic wave propagation in waveguides with an arbitrary cross-section in the time and frequency domain. A weighted residual formulation is used to deliver an efficient hybrid numerical formulation, which is applied to a long pipeline containing a defect of arbitrary shape. The problem is solved first in the frequency domain and then extended to the time domain using an inverse Fourier transform. To separate the scattered wave modes in the time domain, a technique is proposed whereby measurement locations are arranged axially along the pipe and a two dimensional Fourier transform is used to present data in the wavenumberfrequency domain. This enables the separation of highly dispersive modes and the recovery of modal amplitudes. This has the potential to reveal more information about the characteristics of a defect and so may help in distinguishing between different type of defects, such a cracks or regions of corrosion, typically found in pipelines.3

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Acoustic scattering from a wave‐bearing cavity with flexible inlet and outlet

Afzal,

Bilal,

Ahmed

et al. 2023

Math Methods in App Sciences

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In this article, we substantiate the appositeness of the mode‐matching technique to study the scattering response of bridging elastic plates connecting two flexible duct regions of different heights. We present two different solution schemes to analyze the structure‐borne and fluid‐borne radiations in the elastic plate‐bounded waveguide. The first scheme supplements the mode‐matching technique with the so‐called tailored‐Galerkin approach that uses a solution ansatz with homogeneous and integral parts corresponding to the vibrations of the bridging elastic plate and the cavity, respectively. In the second scheme, we supplement the mode‐matching technique with the modal approach wherein the displacement of the bridging elastic plate is projected onto the eigenmodes of the cavity. To handle the non‐orthogonality of the eigenfunctions, we invoke generalized orthogonality relations. An advantage of the proposed mode‐matching schemes is that they provide a convenient way of incorporating a variety of edge conditions on the joints of the plates, including clamped, pin‐joint, or restraint connections. The numerical analysis of the waveguide scattering problems substantiates that edge connections on the joints have a significant impact on the scattering energies and transmission loss. Furthermore, it appears that the transmission loss and structural vibration attenuation in the expansion chamber may be improved by adjusting chamber dimensions and excitation modes.

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Modeling sound propagation in acoustic waveguides using a hybrid numerical method

Cited by 48 publications

References 27 publications

On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

A numerical model for the scattering of elastic waves from a non-axisymmetric defect in a pipe

Acoustic scattering from a wave‐bearing cavity with flexible inlet and outlet

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