Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

Weyna, Stefan; Mickiewicz, Witold

doi:10.2478/aoa-2014-0033

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…The details of using the phase-locked particle image velocimetry along with applying the Proper Orthogonal Decomposition method [13] are shown in the papers by Mickiewicz [11,12] and could be used for such a comparison.…”

Section: Measurement Resultsmentioning

confidence: 99%

A System for Acoustic Field Measurement Employing Cartesian Robot

Szczodrak

Kurowski

Kotus

et al. 2016

Metrology and Measurement Systems

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A system setup for measurements of acoustic field, together with the results of 3D visualisations of acoustic energy flow are presented in the paper. Spatial sampling of the field is performed by a Cartesian robot. Automatization of the measurement process is achieved with the use of a specialized control system. The method is based on measuring the sound pressure (scalar) and particle velocity(vector) quantities. The aim of the system is to collect data with a high precision and repeatability. The system is employed for measurements of acoustic energy flow in the proximity of an artificial head in an anechoic chamber. In the measurement setup an algorithm for generation of the probe movement path is included. The algorithm finds the optimum path of the robot movement, taking into account a given 3D object shape present in the measurement space. The results are presented for two cases, first without any obstacle and the other − with an artificial head in the sound field.

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Section: Measurement Resultsmentioning

confidence: 99%

A System for Acoustic Field Measurement Employing Cartesian Robot

Szczodrak

Kurowski

Kotus

et al. 2016

Metrology and Measurement Systems

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“…Vortex flow can be introduced in fluid systems by modification of the path of flow in order to achieve desired effects. Such modifications include introduction of holes with sharp edges [2], barriers in the path of flow [3], or sudden contraction or expansion as is the case with the SEC [4]. Applications of this phenomenon in vortex motion have been successfully studied by Smith et al, [5] who identified two scattering mechanisms that allow neighbouring modes to interact; scattering occurs at significantly lower frequencies when the mean flow is present; an exchange of energy between mean flow and acoustic field occurs during scattering.…”

Section: Introductionmentioning

confidence: 99%

Effects of Central Tube on Shape of Modal Duct of a Helicoid in a Simple Expansion Chamber

Onyango

Kinyua

Mayaka

2018

Advances in Acoustics and Vibration

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The shape of the modal duct of an acoustic wave propagating in a muffling system varies with the internal geometry. This shape can be either as a result of plane wave propagation or three-dimensional wave propagation. These shapes depict the distribution of acoustic pressure that may be used in the design or modification of mufflers to create resonance at cut-off frequencies and hence achieve noise attenuation or special effects on the output of the noise. This research compares the shapes of acoustic duct modes of two sets of four pitch configurations of a helicoid in a simple expansion chamber with and without a central tube. Models are generated using Autodesk Inventor modeling software and imported into ANSYS 18.2, where a fluid volume from the complex computer-aided-design (CAD) geometry is extracted for three-dimensional (3D) analysis. Mesh is generated to capture the details of the fluid cavity for frequency range between 0 and 2000Hz. After defining acoustic properties, acoustic boundary conditions and loads were defined at inlet and outlet ports before computation. Postprocessed acoustic results of the modal shapes and transmission loss (TL) characteristics of the two configurations were obtained and compared for geometries of the same helical pitch. It was established that whereas plane wave propagation in a simple expansion chamber (SEC) resulted in a clearly defined acoustic pressure pattern across the propagation path, the distribution in the configurations with and without the central tube depicted three-dimensional acoustic wave propagation characteristics, with patterns scattering or consolidating to regions of either very low or very high acoustic pressure differentials. A difference of about 80 decibels between the highest and lowest acoustic pressure levels was observed for the modal duct of the geometry with four turns and with a central tube. On the other hand, the shape of the TL curve shifts from a sinusoidal-shaped profile with well-defined peaks and valleys in definite multiples of π for the simple expansion chamber, while that of the other two configurations depended on the variation in wavelength that affects the location of occurrence of cut-on or cut-off frequency. The geometry with four turns and a central tube had a maximum value of TL of about 90 decibels at approximately 1900Hz.

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“…In conventional acoustic metrology, the analysis of acoustic fields concerns the distribution of pressure levels (scalar variable), however in a real acoustic field, both the scalar (acoustic pressure) and vector (acoustic particle velocity) effects are closely related (Weyna, 2014). Only when the acoustic field is described by both the potential and kinetic energies, it is possible to understand the mechanisms of propagation, diffraction and scattering of acoustic waves on obstacles, as a form of energy image (Weyna, 2003).…”

Section: Introductionmentioning

confidence: 99%

Sound Intensity Distribution Around Organ Pipe

Odya

Kotus

Szczodrak

et al. 2017

Archives of Acoustics

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The aim of the paper was to compare acoustic field around the open and stopped organ pipes. The wooden organ pipe was located in the anechoic chamber and activated with a constant air flow, produced by an external air-compressor. Thus, a long-term steady state response was possible to obtain. Multichannel acoustic vector sensor was used to measure the sound intensity distribution of radiated acoustic energy. Measurements have been carried out on a defined fixed grid of points. A specialized Cartesian robot allowed for a precise positioning of the acoustic probe. The resulted data were processed in order to obtain and visualize the sound intensity distribution around the pipe, taking into account the type of the organ pipe, frequency of the generated sound, the sound pressure level and the direction of acoustic energy propagation. For the open pipe, an additional sound source was identified at the top of the pipe. In this case, the streamlines in front of the pipe are propagated horizontally and in a greater distance than in a case of the stopped pipe, moreover they are directed downwards. For the stopped pipe, the streamlines of the acoustic flow were directed upwards. The results for both pipe types were compared and discussed in the paper.

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Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

Cited by 6 publications

References 15 publications

A System for Acoustic Field Measurement Employing Cartesian Robot

A System for Acoustic Field Measurement Employing Cartesian Robot

Effects of Central Tube on Shape of Modal Duct of a Helicoid in a Simple Expansion Chamber

Sound Intensity Distribution Around Organ Pipe

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