12 results for Pearse, J.R.

  • Patterned fibre constrained layer damping for composite materials

    Verstappen, A.P.; Pearse, J.R. (2014)

    Conference Contributions - Published
    University of Canterbury Library

    Vibration damping is an important consideration in the design of fibre reinforced composite structures as these stiff, lightweight materials often have undesirable vibration transmission characteristics. If not properly addressed, high vibration levels can propagate throughout a composite structure, leading to significant noise levels and reductions in equipment longevity. It is possible to incorporate viscoelastic damping layers into a composite laminate’s construction to achieve improved damping properties. Inclusion of embedded viscoelastic layers results in a constrained layer damping configuration, where the damping capacity is governed by the shear strain in the damping layer. A new composite damping arrangement is proposed where patterned fibre constraining layers are used to increase damping capacity of a viscoelastic mid-layer by inducing additional shear strains. This paper details the design of materials in such a configuration, and the methods used to fabricate and test the damping performance of these patterned fibre constrained layer damping treatments.

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  • The average specific forced radiation wave impedance of a finite rectangular panel

    Davy, J.L.; Larner, D.J.; Wareing, R.R.; Pearse, J.R. (2014)

    Journal Articles
    University of Canterbury Library

    The average specific forced radiation wave impedance of a finite rectangular panel is of importance for the prediction of both sound insulation and sound absorption. In 1982, Thomasson published numerical calculations of the average specific forced radiation wave impedance of a square of side length 2e for wave number k in half octave steps of ke from 0.25 to 64. Thomasson’s calculations were for the case when the forced bending wave number kb was less than or equal to k. Thomasson also published approximate formulas for values of ke above and below the published results. This paper combines Thomasson’s high and low frequency formulas and compares this combined formula with Thomasson’s numerical calculations. The real part of the approximate formula is between 0.7 dB higher and 1 dB lower than the numerical calculations. The imaginary part of the approximate formula is between 2.3 dB higher and 2.6 dB lower than the numerical calculations. This paper also gives approximate formulas for the case when kb is greater than or equal to k. The differences are between 0.8 and 1.2 dB for the imaginary part and between 6.2 and 2.4 dB for the real part.

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  • Design of a standalone, modular test facility for measuring sound transmitted through a common ceiling plenum

    Barclay, E.A.; Wareing, R.W.; Pearse, J.R. (2014)

    Conference Contributions - Published
    University of Canterbury Library

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  • Experimental and computational analysis of the feed accelerator for a decanter centrifuge

    Bell, G.R.A.; Pearse, J.R. (2014)

    Journal Articles
    University of Canterbury Library

    Industrial decanter centrifuges are used in a wide range of industries to separate mixtures of solids and liquids. One of the main elements of these devices is the feed accelerator, which accelerates the incoming mixture to the high rotational speed required for separation. A well-designed feed accelerator can increase product throughput, solids recovery, and liquid clarity, while a poorly designed accelerator can increase wear and reduce the overall efficiency of the machine. This article presents experimental and computational quantification of the performance of six feed accelerator designs that are currently used in decanter centrifuges. The experimental method allowed for the measurement of accelerator and pool speed efficiencies, and high-speed photography of the flow in the annular space between the accelerator and the rotating pool. The computational model allowed for prediction of the flow path in the annular space and the torque imparted on the fluid by the accelerator. A parametric study was conducted using the aforementioned computational model for drum and disk accelerators. It was found that several of the accelerator design parameters were critical to the overall performance, reinforcing the need for an optimised design. It was found that increasing the surface area of the port faces of the drum accelerator and increasing the discharge angle and discharge radius for the disk accelerator improved the performance of the accelerators.

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  • The radiation impedance of a rectangular panel

    Davy, J.L.; Larner, D.J.; Wareing, R.R.; Pearse, J.R. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    This paper extends the definition of the one sided radiation impedance of a panel mounted in an infinite rigid baffle which was previously used by the authors so that it can be applied to all transverse velocity wave types on the panel rather than just to the possibly forced travelling plane transverse velocity waves considered previously by the authors. For the case of plane waves on a rectangular panel with anechoic edge conditions, and for the case of standing waves on a rectangular panel with simply supported edge conditions, the equations resulting from one of the standard reductions from quadruple to double integrals are given. These double integral equations can be reduced to single integral equations, but the versions of these equations given in the literature did not always converge when used with adaptive integral routines and were sometimes slower than the double integral versions. This is because the terms in the integrands in the existing equations have singularities. Although these singularities cancel, they caused problems for the adaptive integral routines. This paper rewrites these equations in a form which removes the singularities and enables the integrals in these equations to be evaluated with adaptive integral routines.

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  • Measurement of Sound in Airflow

    Pearse, J.R.; Kingan, M.J. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    The suitability of a number of different microphone configurations for making sound measurements in airflow was assessed. When a microphone is immersed in airflow, turbulence within the airflow interacts with the diaphragm causing the microphone to measure a noise level, which is due to the turbulence/diaphragm interaction and is not due to an acoustic wave. This turbulence-induced 'pseudo-noise' is equivalent to background noise and can interfere with sound level measurements if the pseudo-noise level is similar to the level of sound being measured. Instances where pseudo-noise may be a problem include measurements made out-doors where the microphone is subjected to atmospheric wind or measurements made in wind tunnels or HVAC ducts. In this paper a number of different microphones and microphone treatments were investigated for their suitability for minimizing pseudo-noise.

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  • Design of Automobile Components for the Minimization of Aeroacoustic Noise

    Kingan, M.J.; Pearse, J.R. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    In recent years, automotive manufacturers have invested significantly in measures to minimize the noise level within an automobile cabin. Today, aeroacoustic noise produced by airflow over car accessories such as vehicle side-mirrors, windscreen wipers and roof carrier systems make a significant contribution to the sound level within the automobile cabin. Consequently, the design of these components to minimize aeroacoustic noise has become important. This paper is concerned with minimizing the aeroacoustic noise of a roof carrier system.

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  • Use of a small low-noise wind tunnel for determining the aeroacoustic noise produced by components on a vehicle

    Kingan, M.J.; Pearse, J.R.; Hubbard, P.D. (2006)

    Journal Articles
    University of Canterbury Library

    This paper describes an experimental method used to determine the aeroacoustic noise produced by a 'roof rack' placed on the roof of a vehicle. Testing was done on a vehicle roof positioned at the outlet jet of a small low-noise wind tunnel. A 'simulated vehicle cabin' was constructed beneath the vehicle roof that had similar absorption characteristics to an actual vehicle cabin. Sound pressure level measurements were made within the simulated vehicle cabin. The sound pressure level measurements were consistent with measurements made within the cabin of an actual vehicle in a large anechoic wind tunnel. The method could also be used to determine the in-cabin aeroacoustic noise produced by other vehicle accessories.

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  • Resonant and Non-Resonant Sound Transmission Loss of a Finite Panel

    Trevathan, J.W.; Pearse, J.R. (2006)

    Journal Articles
    University of Canterbury Library

    The contributions of resonant and non-resonant components to the overall sound transmission through a finite panel have been studied numerically. It was seen that the fundamental mode makes a significant contribution to the non-resonant sound transmission through a finite panel. Therefore, the non-resonant sound transmission loss of a finite panel can be determined, when using a coupled finite element/boundary element analysis, by constructing a structural model with only the fundamental mode in the modal database. The sound transmission loss obtained using this method represents the non-resonant transmission loss of the panel at all frequencies apart from those in the vicinity of the natural frequency of the fundamental mode. The analysis of panels containing higher order modes showed that these modes only contribute to the overall sound transmission loss of a panel at frequencies close to their natural frequencies. The resonant contribution of these higher order modes is reduced by the presence of damping.

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  • The Effect of Workmanship on the Sound Transmission of Airborne Sound through Light Framed Timber Walls

    Trevathan, J.W.; Pearse, J.R. (2007)

    Journal Articles
    University of Canterbury Library

    A study of the airborne sound transmission in a multi-tenanted building has shown that elements of the building which are nominally identical do not have the same acoustic performance. It was seen that some of this variation in performance could be attributed to visually-observable differences in the constructions. Some of the variation could not be explained however, and it was concluded that this variation was due to workmanship. The level of this variation was seen to be approximately 1 dB for a light steel framed construction. This variation is considerably less than that measured previously for a monolithic construction.

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  • Evaluation of the sound insulation of roofing systems

    Mahn, J.; Pearse, J.R. (2010)

    Conference Contributions - Published
    University of Canterbury Library

    The transmission of noise from the outside environment into dwellings is often a concern for the inhabitants. However, the transmission of the noise through the roof is often overlooked when the sound insulation of the dwelling is being assessed unless the dwelling is located near an airport. The transmission of noise through the roof system depends not only on the performance of the roof cladding, but also on the structure-borne noise attenuation of the trusses, the ceiling and the ceiling insulation. In this investigation, the sound insulation of different configurations of roofing systems were evaluated in the laboratory. The configurations tested included variations in the cladding, the sarking installed under the cladding, the thickness of the insulation installed between the ceiling joists and the ceiling construction. The outcome of the study will help to improve the acoustic performance of roofing systems as well as to assist architects in the selection of roofing systems.

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  • The influence of two-dimensional hills on simulated atmospheric boundary layers.

    Pearse, J.R. (1979)

    Doctoral thesis
    University of Canterbury Library

    This thesis describes the development of a number of simulated atmospheric boundary layers and their application to the investigation of wind flow over hills. A review is made of the current knowledge of the wind flow over hills. The atmospheric boundary layer wind tunnel in the Department of Mechanical Engineering was recommissioned and a model 1:300 rural boundary layer established. Measurements of the mean and fluctuating velocities, energy spectra and autocorrelation functions were made in the flow over model two-dimensional triangular hills of slope 3°, 9°, 14° and 27°. Once a certain slope was reached large scale separated flow occurred after the hill crest. The largest increase in velocity occurred for the hill with a slope of 14°. Measurements were also made over round crested hills with the same aspect ratio. Comparison of the flow fields showed that the crest shape had little effect on the flow over the hills. A rural atmospheric boundary layer of 1:3000 scale was established and measurements were made over a selection of the model triangular hills. An increase in the hill height to boundary layer height ratio was found to decrease the amplification factors at the hill crests. Measurements were also made over a number of model triangular hills in an urban model boundary layer of about 1:400 scale which was developed. The effect of the higher velocity gradient was to cause an increase in the amplification factors at the hill crests. A digital data handling system capable of accepting the voltage output from a single hot wire anemometer was developed. Software was written to control the analog to digital converter and transmit the data samples to a minicomputer remote from the wind tunnel. The data samples are stored on disc. When data collection has finished the data is analysed. Software is described which calculates the mean, standard deviation, spectral density function, autocorrelation function and probability density function of the stored data.

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